Search results

Title: Dynamics of the Wind Field Expansion Associated with Extratropically Transitioning Tropical Cyclones.
Creator: Evans, Allen Clark, Hart, Robert, Cunningham, Philip, Krishnamurti, T. N., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Extratropical transition, or ET, can be characterized by the transformation of an initially symmetric, warm-core tropical cyclone into an initially cold-core, asymmetric extratropical cyclone. As a consequence of undergoing transition, changes in the synoptic and dynamic characteristics of the cyclone are realized. Of particular note is the wind field evolution, one of the aspects of ET that has seen little research into its causes. Previous informal theories toward understanding the wind...
Show moreExtratropical transition, or ET, can be characterized by the transformation of an initially symmetric, warm-core tropical cyclone into an initially cold-core, asymmetric extratropical cyclone. As a consequence of undergoing transition, changes in the synoptic and dynamic characteristics of the cyclone are realized. Of particular note is the wind field evolution, one of the aspects of ET that has seen little research into its causes. Previous informal theories toward understanding the wind field evolution based upon key meteorological conservation principles do not accurately account for its observed evolution, while formal studies into other aspects of the ET process (e.g. Ritchie et al. 2001, Jones et al. 2003) have only mentioned its existence or its resultant impacts. This study attempts to bridge this gap by analyzing the physical and dynamical mechanisms involved with both the expansion of the wind field and outward movement of the radial wind maximum during the transition process. One ET case, North Atlantic Tropical Cyclone Bonnie (1998), is modeled using the Pennsylvania State University/NCAR Mesoscale Model version 5 (MM5; Dudhia 1993) at 12km horizontal resolution. The evolution of the cyclone within the model output is found to be an accurate measure of reality when compared to the observed track and dynamical evolution of the cyclone. Analysis of the model output shows that the expansion of the wind field is brought about by the net import of absolute angular momentum from a midlatitude trough of low pressure along descending isentropic trajectories in the western semicircle of the cyclone. Export of absolute angular momentum in the outward branch of the secondary circulation in the eastern semicircle of the cyclone partially negates but does not balance the import to the west; thus a net import of momentum into the cyclone is seen. Redistribution of momentum within the cyclone is accomplished through vertical pressure torques. The overall evolution is found to be consistent with that for a developing extratropical cyclone as shown by Johnson and Downey (1976). Net cooling (warming) inside (outside) of the radial wind maximum is shown to lead to the outward movement of this feature via a hydrostatic response in the radial height gradient, a response opposite to that seen with eyewall contraction (Shapiro and Willoughby 1982) yet consistent with the transition into a cold-core vortex. The observed results are used to formulate a conceptual model for the evolution of the wind field during ET. Implications toward the wind field evolution with other post-ET structural evolutions, such as warm seclusion cyclones and those that remain cold core yet strengthen (e.g. Hart et al. 2006), are drawn in conjunction with the observed results. Related concepts of vertical wind shear and cyclone size are discussed as natural outgrowths of the wind field expansion process.
Show less
Date Issued: 2006
Identifier: FSU_migr_etd-0439
Format: Thesis

Title: The Thermodynamic Evolution of Recurving Tropical Cyclone Bonnie (1998).
Creator: Evans, Allen Clark, Hart, Robert E., Elsner, James B., Krishnamurti, T. N., Reasor, Paul, Ruscher, Paul, Department of Earth, Ocean and Atmospheric Sciences, Florida State...
Show moreEvans, Allen Clark, Hart, Robert E., Elsner, James B., Krishnamurti, T. N., Reasor, Paul, Ruscher, Paul, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: One of the defining characteristics of the extratropical transition of tropical cyclones is the transition of the warm core thermal structure associated with the tropical cyclone into an initially cold core thermal structure associated with the extratropical cyclone. Despite this being a defining characteristic of the extratropical transition process, the literature expresses no consensus agreement upon or a quantification and physical description of the factors that explicitly cause this...
Show moreOne of the defining characteristics of the extratropical transition of tropical cyclones is the transition of the warm core thermal structure associated with the tropical cyclone into an initially cold core thermal structure associated with the extratropical cyclone. Despite this being a defining characteristic of the extratropical transition process, the literature expresses no consensus agreement upon or a quantification and physical description of the factors that explicitly cause this transition to occur. Understanding this evolution is important in order to better forecast and describe the evolution of physical features within the cyclone such as its four-dimensional wind field structure and to begin to quantify the contributors to the poleward transport of heat energy associated with the transitioning cyclone and its impacts upon hemisphere weather patterns and model predictability. This work employs a suite of high resolution numerical simulations in order to quantify and physically describe the evolution of the thermodynamic structure associated with a typical extratropical transition case, North Atlantic Tropical Cyclone Bonnie of 1998. Thermodynamic budgets native to the numerical model's primitive equation set and physical parameterizations are computed during the transition phase of the cyclone within a four-dimensional analysis framework. The observed warm-to-cold thermal profile evolution is found to arise out of an imbalance between dynamical cooling and parameterized warming contributions. This dynamical cooling, as influenced by horizontal advection, vertical advection and adiabatic cooling, and total divergence, is of greater magnitude than warming associated with latent heat release due to condensation and deposition processes within the transitioning cyclone's delta rain region. While the net thermodynamic evolution is found to be relatively resolution-insensitive, specific details of the thermodynamic balance are found to vary depending upon the horizontal resolution of the given numerical simulation. The thermodynamic evolution is ultimately shown to be a natural outgrowth of the factors that influence extratropical transition as a whole and is found to closely resemble the mature and occluding stages of purely cold-core extratropical cyclone development.
Show less
Date Issued: 2009
Identifier: FSU_migr_etd-0440
Format: Thesis

Title: Microwave Radiative Transfer Modeling of Ice in the Atmosphere: A Critical Examination of Cloud Ice Utilizing Remote Sensing.
Creator: Zuiderweg, Adriaan T., Liu, Guosheng, Ruscher, Paul, Kim, KwangYul, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Tropospheric cloud ice has a significant impact on the earth's radiative balance and climate, and to help improve the ability to forecast short-term through climatological-scale weather, the importance of quantification of these ice particles is not to be underestimated. To that end, the study presented here describes an attempt to accomplish large spatial-scale integrated ice water quantity (known as ice water path) retrieval via remote sensing in the microwave band (80-300GHz), where...
Show moreTropospheric cloud ice has a significant impact on the earth's radiative balance and climate, and to help improve the ability to forecast short-term through climatological-scale weather, the importance of quantification of these ice particles is not to be underestimated. To that end, the study presented here describes an attempt to accomplish large spatial-scale integrated ice water quantity (known as ice water path) retrieval via remote sensing in the microwave band (80-300GHz), where effects from ice crystals become detectable via scattering of terrestrial radiation. At the heart of this study is the use of a radiative transfer model in conjunction with data from surface-based instrumentation to simulate atmospheric brightness temperatures at microwave frequencies, and to compare the simulated results to observational data from the Advanced Microwave Sounding Unit - B instrument on the NOAA-15 polar orbiting platform. However, this cannot be done without first discussing the nature of ice crystals in the atmosphere and the scattering modes that result from their interaction with energy, and the implementation of approximations thereof for model usage. Case studies are performed using the model to establish the sensitivity and behavior of the model under differing conditions, and these are compared to real-world data. Subsequently ice water path retrieval from satellite data utilizing Bayesian theory is attempted, with somewhat limited success, and the results hereof are discussed. Finally, known error sources are examined with possibilities for improvement, and ideas for future work in the field presented.
Show less
Date Issued: 2006
Identifier: FSU_migr_etd-0476
Format: Thesis

Title: Spatiotemporal Variability and Prediction of Rainfall over the Eastern Caribbean.
Creator: Pologne, Lawrence, Cai, Ming, Krishnamurti, T. N., Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Recent, recurrent, and extreme weather events have been a cause for concern over the Eastern Caribbean (EC). Given the dependence on rainfall of agriculture, the main stay of the fragile economies throughout the region, accurate and timely forecasts of seasonal rainfall need to be issued to facilitate decision making in Water Resource Management. Understanding the causes of climate variability can lead to the development of more robust models for climate prediction. So as a diagnostic...
Show moreRecent, recurrent, and extreme weather events have been a cause for concern over the Eastern Caribbean (EC). Given the dependence on rainfall of agriculture, the main stay of the fragile economies throughout the region, accurate and timely forecasts of seasonal rainfall need to be issued to facilitate decision making in Water Resource Management. Understanding the causes of climate variability can lead to the development of more robust models for climate prediction. So as a diagnostic approach, different techniques are employed. Empirical Orthogonal Function (EOF) analysis is performed in order to isolate the different modes of rainfall variability as well as investigating their amplitudinal modulations. The evolution of external forcing mechanisms that impact on precipitation extremes is also investigated with the use of composites. Based on the strength of the relationship between Sea Surface Temperature Anomalies (SSTA) and EC rainfall, a statistical model is subsequently developed using multivariate Canonical Correlation Analysis (CCA) to predict rainfall over the region on seasonal time scales. The CCA model demonstrated useful skill in predicting seasonal rainfall over the EC up to six months lead. The highest average predictive skill is realized for the June-July-August (JJA) season at one-month lead, while the lowest average skill is realized for the March-April-May (MAM) season at five months lead. The December-January-February (DJF) season maintained steady skill throughout six months lead. Below normal conditions are forecasted by the CCA model for the 2004/2005 dry season (DJF/2004-05, MAM/2005). This outlook is in part, verified from seasonal rainfall totals at two stations within the EC. The outlook for the coming rainy season is for above normal conditions.
Show less
Date Issued: 2005
Identifier: FSU_migr_etd-0510
Format: Thesis

Title: Assessment of Groundwater Discharge to Lake Barco via Radon Tracing.
Creator: Stringer, Christina Elaine, Burnett, William C., Chanton, Jeffrey P., Sturges, Wilton, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Groundwater-surface water interactions in lakes have been gaining attention in recent years as scientists have recognized the potential significance that groundwater has as a source of nutrients and contaminants to aquatic ecosystems. Such interactions need to be understood in order for us to protect important ecosystems and quantify nutrient loading into lakes. This project set out to test the idea that good estimates could be made of groundwater inputs into Florida lakes using a simple...
Show moreGroundwater-surface water interactions in lakes have been gaining attention in recent years as scientists have recognized the potential significance that groundwater has as a source of nutrients and contaminants to aquatic ecosystems. Such interactions need to be understood in order for us to protect important ecosystems and quantify nutrient loading into lakes. This project set out to test the idea that good estimates could be made of groundwater inputs into Florida lakes using a simple geochemical tracer technique. We hypothesize that a relatively small number of measurements would be sufficient to provide a reasonably good (a factor of 2) estimate of groundwater discharge. Naturally occurring 222Rn makes an ideal tracer because it exists in enriched concentrations in groundwater relative to surface water. We used Lake Barco, a small seepage lake in the Katherine Ordway Preserve, for a detailed pilot study in order to test this hypothesis. The preserve is located about 34 km east of Gainesville, Florida and makes an excellent research site because it is maintained in a pristine state as it is closed off to public access. Two intensive samplings were completed, one in the "dry" season (March 2002) and one in the "wet" season (August 2003). In addition, periodic sampling trips were made to the lake every few weeks to evaluate the spatial and temporal patterns of radon distribution. A 222Rn mass balance was constructed for the lake to evaluate radon fluxes. Once the 222Rn fluxes were determined, groundwater inputs were estimated by dividing these fluxes by the concentration of radon in the water seeping into the lake. The radon concentration is estimated by sediment equilibration experiments using grab samples of sediment and radon activity measurements from monitor wells. We also constructed a traditional hydrologic water budget for Lake Barco. All hydrological variables were either measured or estimated and substituted into a water balance equation, which was then solved for the net groundwater flow term. These estimates were then compared to those from the 222Rn model. Our 222Rn measurements show little discernible spatial variation of radon inventories in the lake on any given day of sampling. Inventories measured at five different stations during the two different intensive sampling trips were all within ±13% of the mean value for each sampling. This amount of variation is considered insignificant, as the estimated analytical variation for the radon measurements is ±10%. We also found that we can estimate the lake inventory at any one station by collecting triplicate samples approximately one meter over the bottom at a single central sampling station. However, our results did display significant temporal variability, responding to rainfall trends that can influence the recharge rates. So, in a lake the size of Lake Barco (12 ha), reasonable groundwater discharge estimates at any given time can be made by triplicate analysis of radon in near-bottom waters and collection and processing of a few sediment samples. The estimations of groundwater discharge to the lake over the period of our study were, on average, 13,000 m3/month and 18,000 m3/month for the radon model and hydrologic budget, respectively. The water balance based estimate might be somewhat low due to differences in hydrogeologic movement under such dry conditions or the large error associated with budget estimations. Considering the large uncertainties in estimating groundwater flow via a hydrologic budget, agreement within a factor of two is considered satisfactory.
Show less
Date Issued: 2004
Identifier: FSU_migr_etd-0395
Format: Thesis

Title: Modeling Streamflow Using Gauge-Only versus Multi-Sensor Rainfall.
Creator: Sullivan, John Lawrence, Fuelberg, Henry E., Ruscher, Paul H., Liu, Guosheng, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: This study evaluates the impacts of two types of rainfall input on simulated streamflow using a specialized, fully-distributed hydrologic model—the Watershed Assessment Model (WAM). We compare gauge-only Thiessen polygon input data with the gridded 4 × 4 km Florida State University (FSU) version of the National Weather Service (NWS) Multi-sensor Precipitation Estimator (MPE) scheme. Streamflow results are compared to observed amounts over a six year period (2000-2005) at two U.S. Geological...
Show moreThis study evaluates the impacts of two types of rainfall input on simulated streamflow using a specialized, fully-distributed hydrologic model—the Watershed Assessment Model (WAM). We compare gauge-only Thiessen polygon input data with the gridded 4 × 4 km Florida State University (FSU) version of the National Weather Service (NWS) Multi-sensor Precipitation Estimator (MPE) scheme. Streamflow results are compared to observed amounts over a six year period (2000-2005) at two U.S. Geological Survey (USGS) stream gauge sites in the greater Florida Suwannee River basin. One catchment has an area of 1505 km2, while the smaller catchment is 500 km2. Previous comparisons have been made between the two different precipitation data types using mean areal precipitation calculations over several Florida basins. This study of streamflow expands on those findings. Results show significant differences in simulated streamflow when the higher-resolution FSU MPE rainfall data are input to WAM. However, the FSU MPE dataset does not always provide better results with this model configuration. The improvements in WAM simulated streamflow depend on a combination of factors, including the desired type of comparison with observed amounts (volume or correlation), rainfall pattern characteristics, and individual event scenarios. The accumulations of FSU MPE WAM streamflow generally are found to be more accurate than those from Thiessen polygons. During drought periods, MPE-derived streamflow provided more accurate accumulations, but coefficients of determination were not always improved. During years with more average rainfall events, FSU MPE produced greater underestimates of accumulation amounts, and thus a better approximation by the Thiessen polygon input. Seasonal results emphasized the weaknesses of each data source. Rain gauges usually are not able to capture the small scale spatial variability of summer rainfall events. And, radar-derived precipitation generally is underestimated during relatively low top stratiform winter events. When simulating streamflow with a hydrologic model using rain gauge input, it is apparent that gauge locations are very important. Generally speaking, increasing the spatial density of gauges will produce a better representation of rainfall. Our small basin was found to be prone to significant underestimates of accumulations and lower coefficients of determination regardless of the rainfall input. However, statistical differences between our larger and smaller basins are not as dramatic with the FSU MPE data. Current results are based on the WAM model as configured for this study. Results from other models and/or other configurations may be different. Although there appear to be errors in both WAM's ability to utilize the rainfall data properly and in the rainfall data measurements themselves, the results highlight areas where both can be improved.
Show less
Date Issued: 2008
Identifier: FSU_migr_etd-0403
Format: Thesis

Title: Metabolic Pathways in Natural Systems: A Tracer Study of Carbon Isotopes.
Creator: Prater, James L., Chanton, Jeffrey P., Wang, Yang, Kostka, Joel E., Mortazavi, Behzad, Burnett, William C., Winchester, John W., Department of Earth, Ocean and Atmospheric...
Show morePrater, James L., Chanton, Jeffrey P., Wang, Yang, Kostka, Joel E., Mortazavi, Behzad, Burnett, William C., Winchester, John W., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: The δ13C value of foliage respiration has been considered a constant in the past and modeling efforts have assumed that the δ13C value of foliage respiration is constant and is directly related to substrate without any fractionation. Consecutive δ13C measurements of foliage dark-respired CO2 (δ13Cr) for slash pine trees (Pinus elliottii) over several diel cycles were used to test the hypothesis that significant variation in δ13Cr would be observed. δ13Cr values collected in daylight from all...
Show moreThe δ13C value of foliage respiration has been considered a constant in the past and modeling efforts have assumed that the δ13C value of foliage respiration is constant and is directly related to substrate without any fractionation. Consecutive δ13C measurements of foliage dark-respired CO2 (δ13Cr) for slash pine trees (Pinus elliottii) over several diel cycles were used to test the hypothesis that significant variation in δ13Cr would be observed. δ13Cr values collected in daylight from all time series showed mid- day 13C enrichment (5 – 10‰) relative to bulk biomass, but values become more 13C depleted following shading and at night and approach bulk-biomass δ13C values by dawn. Assimilation model results suggest that respiration during daylight has the potential to significantly affect ∆13C by as much as 1.6‰, but night dark respiration has little impact on 24-hour integrated ∆13C (0.1‰). We also sampled methane and CO2 from collapse scar bogs (transient permafrost degradation features in permafrost peatlands) to test the hypotheses that microbial respiration and methane production are stimulated by permafrost degradation and collapse and that the fen-like vegetation (i.e. Carex andxi Eriophorum) found in collapse scar bogs near the collapsing edge stimulates acetate fermentation. Our results show that collapse scar bogs have an evolution of spatial variation in methanogenic pathways that is related to surface vegetation cover type. We also demonstrate that changes in stable-isotope fractionation caused by shifts from acetate fermentation and CO2 reduction occur over long time scales (> annual) and are dependent on changes in wetland morphology and surface vegetation cover. We also used radiocarbon as a tracer to test the hypothesis that melting permafrost surrounding the collapse scar bog provides nutrients to the bog-moat location, stimulating the production of radiocarbon-depleted methane. Our results show that the radiocarbon content of methane and DIC at these sites is highly variable and may depend on groundwater input, surface vegetation, and morphological factors associated with the melting permafrost plateau. We conclude that the younger, more labile, carbon stimulating acetate fermentation at one of the sites is supplied by the fen-like surface vegetation, while the older, more recalcitrant, carbon stimulating CO2 reduction at the other site may be supplied by melting permafrost plateau..
Show less
Date Issued: 2005
Identifier: FSU_migr_etd-0429
Format: Thesis

Title: Morphological Barrier Island Changes and Recovery of Dunes after Hurricane Dennis, St. George Island, Florida.
Creator: Priestas, Anthony Michael, Fagherazzi, Sergio, Stallins, J. Anthony, Kish, Stephen, Georgen, Jennifer, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A robust dune system is one of the principal factors in the protection of recreational and residential property within barrier islands. Storm surge from significantly large storm events may remove some or all of the dunes during overwash processes and deposit sediment as washover fans or terraces in the back-barrier. During the summer of 2005, Hurricane Dennis greatly overwashed much of the northwest barrier island chain along the Florida panhandle. The post-storm recovery of dunes and...
Show moreA robust dune system is one of the principal factors in the protection of recreational and residential property within barrier islands. Storm surge from significantly large storm events may remove some or all of the dunes during overwash processes and deposit sediment as washover fans or terraces in the back-barrier. During the summer of 2005, Hurricane Dennis greatly overwashed much of the northwest barrier island chain along the Florida panhandle. The post-storm recovery of dunes and morphological changes occurring after Hurricane Dennis within St. George Island State Park is investigated, in addition to the application of numerical methods as a supplemental tool in determining the post-storm "recovery state" of the barrier and envision morphologic trends. Dune recovery rates are estimated by calculating sediment volume changes of profiles through time. One-dimensional, spatial-series Fourier analysis of individual profiles are used to quantify the recovery and morphologic nature of secondary dunes. Two-dimensional Fourier analysis of elevation data were attempted to be used as a tool to discriminate geomorphic trends in the barrier. Digital elevation models are used to describe post-storm morphologic changes, and the future recovery state of the barrier may be supplemented by analyzing the distributions of curvature and gradients calculated numerically from LIDAR data. Results show that secondary dunes recovered at an average rate of ~3-4 cm per month, and sediment volume changes across transects varied between -1.5 m3/m to1.2 m3/m depending on the presence of vegetation, storm-debris pavement, and proximity to washover deposits. Despite some transects having a net sediment volume loss, all dunes in the presence of vegetation had increased in height. Vegetation did not propagate where storm-debris pavement existed during the one-year duration of the study. The presence of vegetation inhibited dune migration thus favoring dune growth or decreasing the effect of erosion from strong wind events. Fourier analysis of profiles captured changes in dune height at specific wavelengths. The highest energies from the spectra were usually at 30 to 40 meter wavelengths for each profile in time, which reflects the immobility of the dunes and may also reflect the controls of vegetation on dune spacing. The results of two-dimensional Fourier analysis on terrain data were difficult to interpret, but may prove a potential use in terrain analysis. Overwash was prevalent throughout the barrier. For the studied area, St. George Island had experienced inundation overwash with an estimated 100,000 ft3/ft net loss of sediment following the hurricane. Nearly the entire foredune complex was removed, save a few remnants. Storm surge had likely penetrated first in areas where foredunes were either low or discontinuous; in these areas, beach widening was less prevalent. In contrast, the beach widening (~30ft) occurred in areas where the foredunes were higher and more continuous.
Show less
Date Issued: 2009
Identifier: FSU_migr_etd-0458
Format: Thesis

Title: Climatological Characteristics of the Jet Streams over West Africa.
Creator: Suk, Jonathan David, Nicholson, Sharon E., Fuelberg, Henry E., Cai, Ming, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: This paper examines the climatology of the major jet steams over West Africa. Three prominent jets occur at varying heights in the atmosphere, and while each jet is zonal in its flow, their sizes, magnitudes, and directions vary greatly. The Tropical Easterly Jet is shown to be the strongest and most consistent in its location at approximately 200 to 150 hPa. As its name implies, this jet stream consists of easterly flow and has been the topic of many studies over the Tibetan Plateau and...
Show moreThis paper examines the climatology of the major jet steams over West Africa. Three prominent jets occur at varying heights in the atmosphere, and while each jet is zonal in its flow, their sizes, magnitudes, and directions vary greatly. The Tropical Easterly Jet is shown to be the strongest and most consistent in its location at approximately 200 to 150 hPa. As its name implies, this jet stream consists of easterly flow and has been the topic of many studies over the Tibetan Plateau and Indian Ocean due to its relationship with the Indian Monsoon. On a smaller scale, the African Easterly Jet is prominent over West Africa at approximately 700 to 600 hPa. Although it is associated with the African Monsoon, its strength is related to the temperature contrast between the dry desert to its north, and the cool, moist south-westerlies to the south. The third jet stream is the only one that is westerly in direction. It is the least studied of the three jets. The Low Level Westerlies are located between 1000 and 850 hPa. Although they exhibit a smaller velocity, they are believed to exert a significant influence on the precipitation pattern over West Africa. The goal of this project is to determine the climatological characteristics of the three jet streams, especially during the summer months of June, July, August, and September. Along with building a database to analyze the climatological trends of the jets, their interrelationships are also studied. The speed of the Low Level Westerlies is shown to have a significant correlation with the speed of the Tropical Easterly Jet. And, although the African Easterly Jet occurs in the center of the atmospheric column between the other two jets, it does not have a significant relationship to either of the jets located above and below. The conclusions of this paper naturally lend themselves to further research to help explain not only the reason why the Tropical Easterly Jet and the Low Level Westerlies are related, but also the influence that these systems have on the local environment. In addition, future research should determine the larger scale implications of each jet's location in relation to the other jet streams
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0400
Format: Thesis

Title: Ecology of Phytoplankton, Acartia Tonsa, and Microzooplankton in Apalachicola Bay, Florida.
Creator: Putland, Jennifer Nancy, Iverson, Richard, Wise, Sherwood, Marcus, Nancy, Kostka, Joel, Mortazavi, Behzad, Department of Earth, Ocean and Atmospheric Sciences, Florida State...
Show morePutland, Jennifer Nancy, Iverson, Richard, Wise, Sherwood, Marcus, Nancy, Kostka, Joel, Mortazavi, Behzad, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: Apalachicola Bay is a productive estuary located in the northern Gulf of Mexico. The high productivity is, in part, the result of the Apalachicola River delivering freshwater and nutrients to the Bay. Nutrient input supports high levels of phytoplankton productivity, which supports the Bay's secondary productivity. Diversion of water from headwaters of the Apalachicola River during summer has been proposed to satisfy upstream freshwater requirements for recreation and agriculture. Knowledge...
Show moreApalachicola Bay is a productive estuary located in the northern Gulf of Mexico. The high productivity is, in part, the result of the Apalachicola River delivering freshwater and nutrients to the Bay. Nutrient input supports high levels of phytoplankton productivity, which supports the Bay's secondary productivity. Diversion of water from headwaters of the Apalachicola River during summer has been proposed to satisfy upstream freshwater requirements for recreation and agriculture. Knowledge of the ecology of phytoplankton and zooplankton in the Bay is needed to help predict the effects of upstream water diversion on Apalachicola Bay. In this study, the temporal and spatial distribution of phytoplankton size composition, growth, biomass, productivity, microzooplankton bacterivory, herbivory, production, and Acartia tonsa herbivory, carnivory, egg production rate, and egg production efficiency were determined in Apalachicola Bay during 2003 and 2004. Phytoplankton growth, biomass, productivity, total ingestion rates and production rates of microzooplankton, and total ingestion rates and egg production rates of Acartia tonsa peaked during summer within lower salinity (psu) waters. Microzooplankton ingested, on average, ten times more phytoplankton productivity than A. tonsa. Compared to the 24 year average river discharge, river discharge into Apalachicola Bay was above average during 2003 and below average during 2004. On average, 100% and about 50% of the surface salinity of the Bay was 2004, respectively. Nutrient concentrations, at a specific salinity, were higher during 2003 than during 2004. Phytoplankton growth and productivity, as well as total ingestion rates and production rates of microzooplankton, at a specific salinity, were higher during summer 2003 than during summer 2004. It is expected that withdrawal of freshwater from the Apalachicola River during summer will lead to reduced higher trophic level production in Apalachicola Bay because of (1) reduced productivity of phyto- and microzooplankton at a specific salinity and (2) increased areal extent of higher salinity water (>20 psu) where phytoplankton growth, biomass, and productivity and zooplankton productivity is low. Implications of these results are also discussed with respect to our understanding of estuarine planktonic food web structure.20 psu) where phytoplankton growth, biomass, and productivity and zooplankton productivity is low. Implications of these results are also discussed with respect to our understanding of estuarine planktonic food web structure.
Show less
Date Issued: 2005
Identifier: FSU_migr_etd-0505
Format: Thesis

Title: Mixing Corrosion in a Coastal Aquifer.
Creator: Esterson, Kris, Cowart, James B., Lundberg, Neil S., Osmond, John K., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: The coastal aquifer of the northeastern Yucatan peninsula is a mixing zone where freshwater from the platform interior mixes with seawater and saline groundwater to form new brackish solutions. The brackish solutions may form stable flows that move seaward through the aquifer as discrete water parcels. These flows frequently have lowered pH, may be undersaturated with respect to calcite, and may produce significant regional-scale porosity changes due to mixing corrosion.
Date Issued: 2003
Identifier: FSU_migr_etd-0504
Format: Thesis

Title: Development of the Finite-Volume Dynamical Core on the Cubed-Sphere.
Creator: Putman, William M., O'Brien, James J., Lin, Shian-Jiann, Rood, Richard, Krishnamurti, T. N., Navon, I. Michael, Zou, Xiaolei, Department of Earth, Ocean and Atmospheric Sciences...
Show morePutman, William M., O'Brien, James J., Lin, Shian-Jiann, Rood, Richard, Krishnamurti, T. N., Navon, I. Michael, Zou, Xiaolei, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: The finite-volume dynamical core has been developed for quasi-uniform cubed-sphere grids within a flexible modeling framework for direct implementation as a modular component within the global modeling efforts at NASA, GFDL-NOAA, NCAR, DOE and other interested institutions. The shallow water equations serve as a dynamical framework for testing the implementation and the variety of quasi-orthogonal cubed-sphere grids ranging from conformal mappings to those numerically generated via elliptic...
Show moreThe finite-volume dynamical core has been developed for quasi-uniform cubed-sphere grids within a flexible modeling framework for direct implementation as a modular component within the global modeling efforts at NASA, GFDL-NOAA, NCAR, DOE and other interested institutions. The shallow water equations serve as a dynamical framework for testing the implementation and the variety of quasi-orthogonal cubed-sphere grids ranging from conformal mappings to those numerically generated via elliptic solvers. The cubed-sphere finite-volume dynamical core has been parallelized with a 2-dimensional X-Y domain decomposition to achieve optimal scalability to 100,000s of processors on today's high-end computing platforms at horizontal resolutions of 0.25-degrees and finer. The cubed-sphere fvcore is designed to serve as a framework for hydrostatic and non-hydrostatic global simulations at climate (4- to 1-deg) and weather (25- to 5-km) resolutions, pushing the scale of global atmospheric modeling from the climate/synoptic scale to the meso- and cloud-resolving scale.
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0511
Format: Thesis

Title: Multiple Isotopic Tracers for Study of Coastal Hydrological Processes.
Creator: Dulaiova, Henrieta, Burnett, William C., Donoghue, Joseph F., Chanton, Jeffrey P., Landing, William M., Moore, Willard S., Kostka, Joel E., Department of Earth, Ocean and...
Show moreDulaiova, Henrieta, Burnett, William C., Donoghue, Joseph F., Chanton, Jeffrey P., Landing, William M., Moore, Willard S., Kostka, Joel E., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: This study focused on the combined use of radon and radium isotopes as tracers of near-shore geophysical processes including submarine groundwater discharge (SGD), water exchange rates, and atmospheric evasion. Methods were developed for easier measurement of long-lived radium isotopes in natural waters and for continuous radon surveying over larger areas in the coastal zone. These tracer techniques were used to study the mentioned processes at study sites in Shelter Island Sound (New York),...
Show moreThis study focused on the combined use of radon and radium isotopes as tracers of near-shore geophysical processes including submarine groundwater discharge (SGD), water exchange rates, and atmospheric evasion. Methods were developed for easier measurement of long-lived radium isotopes in natural waters and for continuous radon surveying over larger areas in the coastal zone. These tracer techniques were used to study the mentioned processes at study sites in Shelter Island Sound (New York), the Gulf of Thailand, and Apalachicola Bay, Florida. Groundwater fluxes calculated for Shelter Island using isotopic techniques produced results consistent with those measured directly via seepage meters. Groundwater discharge in the Chao Phraya Estuary (Thailand) was shown to be in the range of 2 to 20 m3/s, small compared to river discharge but much higher than seepage rates measured in nearby locations. An experimental assessment of Rn-222 evasion to the atmosphere was performed using radon and Ra-224 profiles in the Chao-Phraya Estuary in Thailand. The different trends in radium and radon isotopes measured in the estuary provided an estimate of atmospheric exchange that agreed with a theoretical approach. Short-lived radium isotopes were applied in a seasonal study of water residence time in Apalachicola Bay, Florida. The water transport within different sectors of the bay was evaluated as a result of advective (estuarine) and dispersive physical mixing. The distribution of the radium isotope ratios was used to determine apparent radium ages of the water within the bay. The results clearly showed how the water-residence time in the bay changes seasonally and that the winds and tides influence the water circulation in the bay. The radium tracer approach gave turnover times of 6 to 12 days in Apalachicola Bay during the studied periods.
Show less
Date Issued: 2005
Identifier: FSU_migr_etd-0643
Format: Thesis

Title: Interannual Flow off Southern California and Its Influence on Water Properties and Marine Life.
Creator: Dottori, Marcelo, Clarke, Allan J., Tam, Christopher, Nof, Doron, Weatherly, Georges, Dittmar, Thorsten, Department of Earth, Ocean and Atmospheric Sciences, Florida State...
Show moreDottori, Marcelo, Clarke, Allan J., Tam, Christopher, Nof, Doron, Weatherly, Georges, Dittmar, Thorsten, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: Lagged correlation of dynamic height from the gappy California Cooperative Oceanic Fisheries Investigation (CalCOFI) with monthly San Diego sea level for the period 1949-2001 shows that the dynamic height propagates westward at 4.10 cm/s, about double the speed of the large-scale low frequency Rossby wave (2.2 cm/s). TOPEX/Poseidon/Jason1 along-track sea level height estimates since January 1993, filtered interannually, propagate westward at 4.3 cm/s, verifying that observed westward...
Show moreLagged correlation of dynamic height from the gappy California Cooperative Oceanic Fisheries Investigation (CalCOFI) with monthly San Diego sea level for the period 1949-2001 shows that the dynamic height propagates westward at 4.10 cm/s, about double the speed of the large-scale low frequency Rossby wave (2.2 cm/s). TOPEX/Poseidon/Jason1 along-track sea level height estimates since January 1993, filtered interannually, propagate westward at 4.3 cm/s, verifying that observed westward propagation is about double that expected. Including the effect of the mean California current on the Rossby wave propagation does not explain the discrepancy but rather slightly increases it. Because of the westward propagation, interannual variations in alongshore geostrophic surface current are proportional to the time derivative of sea level. This means that such large scale interannual current variability can be monitored with appropriate lag, by the time derivative of coastal sea level. The anomalous alongshore flow advects particles, the anomalous alongshore particle displacement being proportional to sea level. Since nutrient concentration is lower in the south, the anomalous alongshore displacement results in lower nutrient concentration when sea level is anomalously high and higher nutrient concentration when the sea level is anomalously low. Vertical displacement also results in a similar relationship between nutrients and sea level. The anomalous alongshore and vertical particle displacements associated with the Rossby waves also act on the mean temperature and salinity fields to produce temperature and salinity anomalies. Theory suggests that these anomalies should be proportional to the anomalous dynamic height. Consistent with this, observed salinity anomalies at depths of 100-200 m are well correlated with dynamic height anomalies. At depths greater than 200 m the observed anomalies are small and, consistent with a smaller signal to noise ratio, the correlation falls. At depths shallower than 100 m the correlation between salinity and dynamic height anomalies also falls rapidly. The flow anomalies can similarly be used to explain the temperature fluctuations except that the correlation between temperature and dynamic height fluctuations does not fall rapidly in the surface layer as in the salinity case.
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0684
Format: Thesis

Title: Statistical Prediction of Tropical Cyclone Intensity Using Dynamical and Thermodynamical Inner-Core Parameters Derived from Hwrf Analysis and Forecasts.
Creator: Zelinsky, David A., Co-, T.N. Krishnamurti, Co-, Paul Ruscher, Misra, Vasu, Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A new multiple linear regression model for short range tropical cyclone intensity prediction is developed. Four new dynamical and thermodynamical predictors based on HWRF output are considered: (1) the horizontal advection of relative angular momentum, (2) energy exchange from the divergent to the rotational kinetic energy (Psi-Chi interactions), (3) the conversion of shear vorticity to curvature vorticity, and (4) the vertical differential of heating in the complete potential vorticity...
Show moreA new multiple linear regression model for short range tropical cyclone intensity prediction is developed. Four new dynamical and thermodynamical predictors based on HWRF output are considered: (1) the horizontal advection of relative angular momentum, (2) energy exchange from the divergent to the rotational kinetic energy (Psi-Chi interactions), (3) the conversion of shear vorticity to curvature vorticity, and (4) the vertical differential of heating in the complete potential vorticity equation. Predictors were calculated using Hurricane Research Weather and Forecast (HWRF) model initial fields. Each predictor was determined to exhibit a statistically significant relationship with 12 hour intensity change in tropical cyclones by an F-test. The predictors were then used as the basis for a multiple linear regression model, following the methodology of the operational Statistical Hurricane Intensity Prediction Scheme (SHIPS). Four additional predictors, intended to represent basic storm information and environmental conditions, were included in the development of a second model. Retrospective forecasts of hurricanes in 2004, 2005, and 2006 were created for both models, and compared to operational SHIPS and HWRF forecasts. Despite relying on HWRF fields for the calculation of predictors, the new model produces better forecasts than HWRF for short term (less than 48-hr) forecasts. Additional methods were developed to extend forecasts beyond 48 hours. This resulted in a systematic improvement of HWRF forecasts. It is proposed that the new model could be used operationally as a new version of the "early" HWRF.
Show less
Date Issued: 2011
Identifier: FSU_migr_etd-0585
Format: Thesis

Title: The Effect of Radiative Transfer on the Atlantic Subtropical Anticyclone and Hurricane Steering.
Creator: Diaz, Dante Christopher, Krishnamurti, T. N., Hart, Robert E., Liu, Guosheng, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: This study explores sensitivity of the Atlantic subtropical anticyclone and the tracks of tropical cyclones traveling around the subtropical anticyclone to radiative transfer. The data sets for these experiments are derived from 120-hours forecasts generated using the T126 version of the Florida State University Global Spectral Model (FSUGSM). The subtropical anticyclone owes its origin, maintenance, and its asymmetrical nature over the Atlantic Ocean mainly due to radiative cooling over the...
Show moreThis study explores sensitivity of the Atlantic subtropical anticyclone and the tracks of tropical cyclones traveling around the subtropical anticyclone to radiative transfer. The data sets for these experiments are derived from 120-hours forecasts generated using the T126 version of the Florida State University Global Spectral Model (FSUGSM). The subtropical anticyclone owes its origin, maintenance, and its asymmetrical nature over the Atlantic Ocean mainly due to radiative cooling over the eastern ocean. This being the case, it follows that the way radiative properties are modeled will play a crucial role in determining the reliability of a forecast. In order to examine this, the full FSUGSM is compared to a version with no radiative properties. This represents the most extreme case and shows the significance of radiative properties on not only the subtropical anticyclone, but also the flow associated with it, and thus the tracks of tropical cyclones traversing the Atlantic Ocean. Since the subtropical anticyclone is the dominant factor in the steering flow, it follows that changes in the tropical cyclones' tracks occur in concert with changes seen in the anticyclone under different radiative conditions. The effects of (no) radiation take about three days to manifest themselves. The subtropical high weakens, and broadens westward without radiative cooling to maintain it. In turn, the orientation of the subtropical high changes as does the steering pattern. Due to this there is a change seen in the tracks of the tropical cyclones. The cyclones are more to the west and south compared to the normal model. Thus, radiation is an important factor in the forecasts of tropical cyclones and their steering environment three days or greater.
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0738
Format: Thesis

Title: Effect Hypoxia Has on Feeding and Egg Production Rates of Acartia Tonsa Dana 1849 (Copepoda: Calanoida).
Creator: Sedlacek, Chris, Marcus, Nancy, Thistle, David, Kostka, Joel, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Low oxygen conditions in the water column or hypoxia occur in estuaries and impact more than just the obvious commercially important species. Copepods are an important link in the food web and the influence of hypoxia upon them is relatively unstudied. Using the copepod Acartia tonsa, a study of the impact of hypoxia on egg production and feeding was conducted. A. tonsa decreased egg production at lower dissolved oxygen concentrations (DO), with the lowest egg production occurring at 0.53-ml...
Show moreLow oxygen conditions in the water column or hypoxia occur in estuaries and impact more than just the obvious commercially important species. Copepods are an important link in the food web and the influence of hypoxia upon them is relatively unstudied. Using the copepod Acartia tonsa, a study of the impact of hypoxia on egg production and feeding was conducted. A. tonsa decreased egg production at lower dissolved oxygen concentrations (DO), with the lowest egg production occurring at 0.53-ml/l O2 concentration. However as the DO decreased the amount of chlorophyll a in the gut of the copepods increased. Also as DO decreased the number of fecal pellets decreased, indicating that feeding was being suppressed. Another experiment was conducted to determine if by increasing food concentration the affect of hypoxia could be mitigated. The results indicate that increased food did not offset the impact hypoxia has on egg production of A. tonsa. These results suggest that as A. tonsa experiences hypoxia in the wild, population numbers will decrease. Thus if hypoxic conditions increase in scope and duration declines in copepod abundance may very well lead to a decline in the abundance of species that depend on them as food. These species may be of commercial importance.
Show less
Date Issued: 2003
Identifier: FSU_migr_etd-0285
Format: Thesis

Title: The Impacts of Macrobenthos on the Rates and Pathways of Organic Matter Mineralization in Two Coastal Marine Ecosystems of the Southeastern United States.
Creator: Smith, April Christine, Kostka, Joel E., Balkwill, David, Thistle, David, Marcus, Nancy, Devereux, Richard, Furukawa, Yoko, Department of Earth, Ocean and Atmospheric Sciences,...
Show moreSmith, April Christine, Kostka, Joel E., Balkwill, David, Thistle, David, Marcus, Nancy, Devereux, Richard, Furukawa, Yoko, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: Coastal ecosystems are among the most productive in the world, and they serve as an invaluable resource to society. Despite many decades of biogeochemical research in the coastal zone, carbon and nutrient budgets remain uncertain largely due to the inherent complexity and spatiotemporal variability observed in coastal ecosystems. This dissertation addresses the rates, pathways, and microorganisms responsible for organic-matter mineralization and nutrient release in the sediments of coastal...
Show moreCoastal ecosystems are among the most productive in the world, and they serve as an invaluable resource to society. Despite many decades of biogeochemical research in the coastal zone, carbon and nutrient budgets remain uncertain largely due to the inherent complexity and spatiotemporal variability observed in coastal ecosystems. This dissertation addresses the rates, pathways, and microorganisms responsible for organic-matter mineralization and nutrient release in the sediments of coastal marine ecosystems. In particular, the research herein focuses on the role of macrobenthos and spatial/ temporal variability in impacting organic matter and nutrient cycles in such ecosystems. The common theme throughout the dissertation research was to combine ecology with biogeochemistry to explore the impacts of benthic organisms in the macroscale on microbial processes that mediate organic matter mineralization and nutrient release over the microscale. Sulfate-reducing prokaryotes (SRP) play a key role in carbon and nutrient cycles of coastal marine, vegetated ecosystems, but interactions of SRP communities with aquatic plants remain little studied. In the subtidal zone of Santa Rosa Sound, Florida, SRP abundance, activity, and community composition were studied in relation to sediment geochemical gradients and plant growth state in a Thalassia testudinum seagrass bed and in adjacent unvegetated areas (Chapter 1). The community composition of SRP was determined using restriction fragment length polymorphism (RFLP) screening and amino acid sequence comparisons inferred from partial dissimilatory bisulfite reductase (dsrA and B) genes that were PCR-amplified and cloned from DNA extracted from sediment samples. Our results indicate that seagrass growth state affects the abundance and activity of SRP, while SRP community composition remains relatively stable across the environmental parameters tested. Sequence data from this study may be used to direct future cultivation efforts and to design new genetic probes for sulfate-reducers in seagrass sediments. The remaining dissertation research focused on a second coastal marine ecosystem, the saltmarsh, on Skidaway Island near Savannah, Georgia. The Georgia saltmarsh contrasts with seagrass beds from the west coast of Florida in that it exists in the intertidal zone, contains a large tidal range of 2-3 m, and the sediments are exposed to extensive burrowing and feeding activities by macrofauna. In addition, larger seasonal change may be observed in the Georgia marsh because it is intertidal and exposed to slightly larger annual temperature extremes. In chapter two, extensive biogeochemical field characterization was combined with state-of-the-art diagenetic modeling to elucidate feedbacks between macrobenthic organisms (macrophyte plants, bioturbating macrofauna) and the controls of organic matter mineralization in saltmarsh sediments. A multicomponent, inverse model was used to support the field work by quantifying properties and processes that in some cases could not be experimentally determined. Modeled rates of organic matter diagenesis were determined by attempting to find the best agreement with measured profiles of major redox species. Results indicated that sulfate reduction is the dominant degradation pathway for sites with less bioturbation, while iron reduction outcompeted sulfate reduction where intense bioturbation activity caused the rapid recycling of Fe(III)-oxyhydroxides. These results were fairly consistent across seasons, however, the magnitude of degradation rates decreased dramatically in the winter, and microbial sulfate reduction was more greatly affected by changes in temperature than microbial iron reduction. The objective of the third and final study was to scale up biogeochemical measurements over an entire ecosystem (saltmarsh basin) in order to address spatial variability that has confounded estimates of organic matter and nutrient mineralization at the whole ecosystem level. A 100,000 m2 area of Georgia marsh was mapped using a combination of aerial photography, Geographic Information Systems (GIS), and localized identification of plant types. Major habitats were delineated according to the predominant vegetation, including the short form of Spartina alterniflora (SS), the tall form of S. alterniflora (TS) and unvegetated creekbank (CB). Spatial variability was addressed across all major habitats with a statistically-sound experimental design to carry out determinations of porewater and solid-phase geochemistry, sulfate reduction rates (SRR), bacterial abundances, macrofaunal burrow size/density, plant stem height/density, and above/belowground plant biomass. Habitat type had a large influence on the rates and pathways of carbon oxidation. Consideration of spatial variability revealed that overall carbon oxidation rates in saltmarsh ecosystems may be higher than previously thought. Surprisingly, microbial Fe(III) reduction (and not sulfate reduction) was observed to be the predominant terminal-electron-accepting process coupled to carbon oxidation for the majority of the marsh basin studied. Together with the observation that most of the Georgia marsh studied was not sulfidic, results indicate that our perceptions of the redox poise, and the impacts of redox poise on biogeochemical cycles, need to be revised for marsh ecosystems taking into account spatial variability driven by macrobenthic activities. Typically, coastal sediments rapidly become anaerobic just below the sediment surface, and the flux of oxidants into sediments is limited. Under these conditions, anaerobic bacteria are responsible for the majority of organic matter remineralization. Increased solute and particle transport via macroorganismal activities (bioturbation, bioirrigation, and phytoirrigation) aids in mixing reactants throughout sediments, thereby encouraging microbial activities, and increasing organic matter remineralization rates. The following research employed an array of new and diverse multidisciplinary approaches from molecular biological techniques and GIS mapping to state-of-the-art diagenetic modeling in order to elucidate the impacts of macrobenthos on carbon and nutrient cycles mediated by anaerobic microorganisms in coastal marine ecosystems. In all three studies, geochemical parameters indicated that bacterial activities were stimulated in vegetated sediments, while saltmarsh studies revealed that macrofaunal burrows strongly influenced the pathways of terminal electron acceptor (TEA) usage. The uncertainty of current estimates of carbon and nitrogen cycling in saltmarsh habitats indicates the need for a more comprehensive approach to address the spatial variability that exists in these habitats. From the research reported in this dissertation, it is clear that macrobenthos have a profound impact on the rates and pathways of organic matter mineralization and that the resulting spatial variability in sediment biogeochemical cycles must be incorporated into future studies that attempt to determine elemental budgets in coastal marine ecosystems.
Show less
Date Issued: 2004
Identifier: FSU_migr_etd-0343
Format: Thesis

Title: Characteristics of Decaying Storms during Lightning Cessation at Kennedy Space Center and Cape Canaveral Air Force Station.
Creator: Anderson, Holly Alison, Fuelberg, Henry E., Ruscher, Paul H., Hart, Robert E., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Improved knowledge of thunderstorm behavior near the end of its lifecycle is essential to improving the prediction of lightning cessation. This study documents the characteristics of decaying storms near the end of their lightning activity at Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). Total lightning data were obtained by combining information from the Lightning Detection and Ranging (LDAR) network with the Cloud-to-Ground-Surveillance System (CGLSS) and the...
Show moreImproved knowledge of thunderstorm behavior near the end of its lifecycle is essential to improving the prediction of lightning cessation. This study documents the characteristics of decaying storms near the end of their lightning activity at Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). Total lightning data were obtained by combining information from the Lightning Detection and Ranging (LDAR) network with the Cloud-to-Ground-Surveillance System (CGLSS) and the National Lightning Detection Network (NLDN). The lightning data were used in conjunction with WSR-88D radar data and Rapid Update Cycle (RUC) model analyses. The study focuses on a dataset of 116 isolated unicellular and multicellular storms during the warm-seasons (May-September) of 2000-2005. Twenty of the 116 storms were tracked through lightning cessation using the K-Means storm clustering and tracking algorithm within the Warning Decision Support System – Integrated Information (WDSS-II). This tracking yielded time-series of radar-derived, RUC-derived, and lightning parameters. Flash characteristics of the 116 storms showed trends during storm growth and dissipation; however, none exhibited clear relationships with the final flash. Although most storms experienced gradually decaying flash rates until cessation, two other cessation behaviors also were observed, making flash activity an unreliable indicator of cessation. Trends in composite reflectivity, reflectivity at three temperatures crucial to storm electrification (i.e., 0°C, -10°C, -20°C), storm thickness of 30 dBZ above -10°C, and vertical gradients of reflectivity were analyzed for 20 storms during the 8 min period prior to cessation to determine if any indicated imminent cessation. Results showed substantial variability in the decaying storms. Although these parameters decreased in most storms during the 8 min period, some increased. Distributions of the parameters at the last flash also were considered, but no clearly preferred value was evident at the last flash. Neither the inversion of lightning initiation criteria (e.g., 40 dBZ at -10°C) nor the descent of 45 dBZ below -10°C were found to be a useful indicator of cessation. Previously-documented lightning "bubbles" of LDAR sources were observed and were consistent with pulses in the intensifying updrafts. The last lightning "bubble" signatures were found to precede lightning cessation by ~35 min.
Show less
Date Issued: 2010
Identifier: FSU_migr_etd-0197
Format: Thesis

Title: Variability of Intraseasonal Precipitation Extremes Associated with ENSO in Panama.
Creator: Arrocha, Gloria, O'Brien, James J., Ruscher, Paul, Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Extensive analysis has been conducted over past decades showing the impacts of El Niño-Southern Oscillation (ENSO) on various regions throughout the world. However, these studies have not analyzed data from many stations in Panama, or they have not analyzed long periods of observations. For these reasons, they often miss climatological differences within the region induced by topography, or they do not possess enough observations to adequately study its climatology. Accordingly, the current...
Show moreExtensive analysis has been conducted over past decades showing the impacts of El Niño-Southern Oscillation (ENSO) on various regions throughout the world. However, these studies have not analyzed data from many stations in Panama, or they have not analyzed long periods of observations. For these reasons, they often miss climatological differences within the region induced by topography, or they do not possess enough observations to adequately study its climatology. Accordingly, the current study focuses on ENSO impacts on precipitation specific to the Isthmus of Panama. Results will be useful for agricultural and water resources planning and Panama Canal operations. Monthly total precipitation data were provided by Empresa de Transmisión Eléctrica S.A., which includes 32 stations with records from 1960 to 2004. The year is split into three seasons: two wet seasons (Early and Late Wet), one dry season (Dry). The country is also divided into regions according to similarities in the stations' climatology and geographic locations. Upper and lower precipitation extremes are associated with one of the three ENSO phases (warm, cold or neutral) to estimate their percentages of occurrences. The differences between each ENSO phases' seasonal precipitation distributions are statistically examined. Statistical analyses show effects of ENSO phases that vary by season and geographical region. Cold and warm ENSO years affect the southwestern half of the country considerably during the Late Wet season. Cold ENSO phases tend to increase rainfall, and the warm phase tends to decrease it. The opposite is true for the Caribbean coast. The Dry season experiences drier conditions in warm ENSO years, and the Early Wet season does not show any statistically significant difference between ENSO years' rainfall distributions.
Show less
Date Issued: 2006
Identifier: FSU_migr_etd-0237
Format: Thesis

Title: The Bering Strait and the Southern Ocean Winds' Grip on the World Climate.
Creator: De Boer, Agatha M., Nof, Doron, Hunter, Christopher, Burnett, William, Clarke, Alan J., Speer, Kevin, Weatherly, Georges L., Department of Earth, Ocean and Atmospheric Sciences,...
Show moreDe Boer, Agatha M., Nof, Doron, Hunter, Christopher, Burnett, William, Clarke, Alan J., Speer, Kevin, Weatherly, Georges L., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: The Bering Strait's Grip On The World Climate: The Holocene interglacial period of the last 10,000 years and the penultimate interglacial ~125,000 years ago have been characterized by distinctly stable climates. During the intervening glacial period, climate records are marked by rapid large-amplitude oscillations, general known as Dansgaard-Oeschger events. These millennial-scale cycles are generally believed to be a result of freshwater anomalies in the North-Atlantic, followed by a...
Show moreThe Bering Strait's Grip On The World Climate: The Holocene interglacial period of the last 10,000 years and the penultimate interglacial ~125,000 years ago have been characterized by distinctly stable climates. During the intervening glacial period, climate records are marked by rapid large-amplitude oscillations, general known as Dansgaard-Oeschger events. These millennial-scale cycles are generally believed to be a result of freshwater anomalies in the North-Atlantic, followed by a reorganization of the thermohaline circulation. Here, we propose that such long lasting instabilities in the thermohaline circulation are only possible during glacial periods when the Bering Strait (BS) is closed. A semi-global analytical ocean model (which includes both wind and thermohaline processes) is used to show that, during interglacial periods (when the BS is open) perturbations in North Atlantic Deep Water (NADW) formation are rapidly damped out because of a novel BS freshwater feedback mechanism. This new feedback mechanism is due to the strong winds in the Southern Ocean (SO) which, with an open BS, quickly [O(10)years)] flush any low salinity anomalies out of the Atlantic and into the Pacific Ocean. During glacial periods, the stabilizing feedback is prevented by the closure of the BS which traps the anomalies within the Atlantic, causing long lasting perturbations. The sensitivity of the mean stable state to steady changes in the external forcing, namely the wind or the precipitation field, is also tested. A relevant example is a prolonged increase in precipitation due to anthropogenic warming, (predicted by global circulation models). We find that both stronger winds (especially the SO Winds) and a decrease in precipitation over the North Atlantic (NA) will lead to a new (stable) enhanced overturning. Conversely, weaker winds or increased precipitation will reduce the overturning to a slower stable state. The Island Wind-Bouyancy Paradox: In reent years, a variety of studies have suggested that the meridional overturning circulation is at least partially controlled by the Southern Ocean winds. The paraadoxical implication is that a link exists between the surface bouyancy flux to the ocean (which is needed for the density transfor4matio between surface and deep water) and the wind. These forcings have traditionally been viewed as independent drivers of the ocean circulation. Here, the paradox is formally stated in the framework of a gigantic island that lies between latitude bands free of continents (such as the land mass of the Americas). The choice of such an island on a sphere was made because it enables one to obtain analytical solutions and it circumvents the need to calculate the torque exerted on zonal sills adjacent to the island tips (e.g., the Bering Strait). The torque calculation is notoriously difficult and is avoided here by the clockwise integration which goes twice through the western boundary of the island (in opposite directions) eliminating any unknown pressure torques. The derived wind-driven overturning is shown to be consistent with Godfrey's Island Rule when the rule is extended to include the sinking or upwelling adjacent to the island. In addition, the consideration of vertical exchange in the Island Rule eliminates the need to make the level-of-no-motion assumption. The paradox is resolved quanlitatively, using salinity and temperature mixed dynamical-box models and a temperature slab model, and quantitatively, employing a numerical model. We show that in all cases the ocean stratification and thermocline depth adjust themselves to allow the overturning imposed by the wind. The salinity and temperature box model suggests that stronger southern winds will tend to weaken the virtical and horizontal salinity stratfication so that it is esier for the conversion of deep to surface water (and vice versa) to take place. A temperature slab model (i.e., y-dependent)offers a more detailed picture;stronger southern winds flatten the meridional temperature profile and shift it northwards (so that it lags the atmospheric temperature). The (process orientated) numericl model is adapted to include a thermodynamic parameterization for the surface heat and freshwater fluxes. In response to stronger southern winds, the thermocline thickens in the north, releases more heat to the atmosphere and, therefore, converts more surface to deep water.
Show less
Date Issued: 2003
Identifier: FSU_migr_etd-0336
Format: Thesis

Title: Attributing Contributions to the Seasonal Cycle of Anthropogenic Warming in a Simple Radiative- Convective Global Energy Balance Model.
Creator: Sejas, Sergio A., Cai, Ming, Ellingson, Robert G., Wu, Zhaohua, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A simple one-dimensional seasonal atmosphere-ocean energy balance model is used to study the seasonal and latitudinal response of the model climate to a doubling of the CO2 concentration. A new climate feedback analysis method, formulated in Lu and Cai (2009a), is used to isolate contributions (partial temperature changes) of the external forcing alone and subsequent feedbacks to the total temperature change experienced by the model climate. In this study, the relative importance of the...
Show moreA simple one-dimensional seasonal atmosphere-ocean energy balance model is used to study the seasonal and latitudinal response of the model climate to a doubling of the CO2 concentration. A new climate feedback analysis method, formulated in Lu and Cai (2009a), is used to isolate contributions (partial temperature changes) of the external forcing alone and subsequent feedbacks to the total temperature change experienced by the model climate. In this study, the relative importance of the external forcing alone (the CO2 doubling), surface ice-albedo feedback, water vapor feedback, changes in poleward heat transport, changes in vertical sensible heat flux, and changes in heat storage are analyzed. The partial temperature change due to the water vapor feedback is substantially the largest contributor to the globally averaged surface warming. The ice-albedo feedback plays a smaller role, but also significantly contributes to the overall warming of the surface. The most important negative feedback, counteracting the surface warming, is the change in the vertical sensible heat flux. However, though the water vapor feedback is most responsible for the overall surface warming, it is not the feedback most responsible for the seasonal and spatial pattern of the surface warming. The climate of this model indicates that there is a surface polar warming amplification, with a maximum occurring in late summer/early fall. The feedback most responsible for this polar warming amplification and seasonal pattern in this model is the surface ice-albedo feedback, which is largest at high latitudes in summer.
Show less
Date Issued: 2011
Identifier: FSU_migr_etd-0278
Format: Thesis

Title: Impacts of Deep-Sea Carbon Sequestration and of Ciliate Epibionts on Harpacticoid Copepods.
Creator: Sedlacek, Linda, Thistle, David, Wulff, Janie, Marcus, Nancy, Huettel, Markus, Burnett, William, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: One way to slow down global warming is to reduce the amount of carbon dioxide released into the atmosphere by capturing carbon dioxide from point sources (e.g., power plants) and storing it out of contact with the atmosphere. One storage site that is being considered is the deep-sea floor. Below ~2600 m, carbon dioxide is a liquid and is denser than seawater, so carbon dioxide poured into a depression would create a carbon dioxide lake. The environmental consequences of this disposal option...
Show moreOne way to slow down global warming is to reduce the amount of carbon dioxide released into the atmosphere by capturing carbon dioxide from point sources (e.g., power plants) and storing it out of contact with the atmosphere. One storage site that is being considered is the deep-sea floor. Below ~2600 m, carbon dioxide is a liquid and is denser than seawater, so carbon dioxide poured into a depression would create a carbon dioxide lake. The environmental consequences of this disposal option are largely unknown. This study tries to address the environmental consquences by studying the effects of carbon dioxide-rich seawater on organisms at various distance from a carbon-dioxide source. Harpacticoids were chosen as the study organism because they are abundant and may be an important prey item in the deep sea. To determine if the carbon dioxide-rich seawater affected the harpacticoids, a seven metrics were used. Overall, none of the metrics indicated that exposure to carbon dioxide-rich seawater had an effect. A previous study found a very different result. A comparison of the two studies revealed that the difference in flow dynamics between the two stations in the two experiments could explain the dichotomy, raising the possibility that deep-sea benthic environments that experience slower flow may be better disposal sites. Harpacticoids in the deep-sea sometimes harbor ciliate epibionts. Their presence may influence a harpacticoid's ability to deal with the stress imposed by carbon-dioxide rich seawater. As a first step in trying to understand the harpacticoid-epibiont relationship, I identified the epibionts and determined whether or not they occurred more frequently on adults, on one host species more than the others, on one host sex more than another, or on one portion of a host more than another portion at the control site. Three epibiont species were abundant enough to analyze, Loricophrya sp., Trachelolophos sp., and Vorticella sp. Loricophrya sp. and Trachelolophos sp. individuals attached only to the antennules of Nitokra sp. and occurred significantly more often on this species than on other species. Vorticella sp. individuals attached significantly more frequently to Ameira sp. and Mesocletodes cf. irrasus than to other species. Individuals of Vorticella sp. were found attached to the side of the cephalosome, to the region of the mouth parts, and to the body between the swimming legs. Specificity in host usage was unexpected because harpacticoid individuals of a given species are sparse in the deep-sea. I did not find that any of the epibiont species occurred on one sex more than the other. One method that epibionts may use in order to be host specific is to attach to species that are relatively abundant. I then examined the potential effect that the epibionts had on their hosts. To do so, I compared the harpacticoids at the 2-m site (treatment area) and 75-m site (control area). I found that only for individuals of Nitokra sp. with individuals of Loricophrya sp. attached was there a significantly higher proportion of host individuals with epibionts in the treatment area than in the control area. None of the host species showed a difference in the average number of epibionts they carried in the control area and the treatment area. These results suggest that individuals of Nitokra sp. were capable of resisting the attachment of the first individual of Loricophrya sp., but that individuals of Nitokra sp. were unable to continue to resist after the first Loricophrya sp. individual attached. Trachelolophos sp. was always with Loricophrya sp., so for the analyses that examined the proportion of host individuals that were alive at the time of collection, the group of harpacticoids that had only Loricophrya sp. (= L.) and those with both Trachelolophos sp. and Loricophrya sp. (= L. + T.) were analyzed together (= L. and L. + T.). In the treatment area, the proportion of individuals of Nitokra sp. that were alive at the time of collection was greater when individuals of L. and L. + T. were attached than when they not. In the control area, the proportion of individuals of Ameira sp. that were alive at the time of collection was greater when individuals of Vorticella sp. were attached than when they were not. In general, the effect of the epibionts on their host harpacticoids appears to be positive, an unexpected result considering that positive effects have not been found before.
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0284
Format: Thesis

Title: The Biochemical Composition of Naupii Derived from Stored Non-Diapause and Diapause Copepod Eggs and the Biology of Diapausing Eggs.
Creator: Sedlacek, Christopher, Marcus, Nancy, Keller, Laura, Thistle, David, Huettel, Markus, Kostka, Joel, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Mariculture of fish is needed to support our ever growing global population. Copepods are a natural and beneficial source of first feed for many marine fish species, but it can be difficult to hatch enough when the fish are ready to feed. Therefore, storage of copepod eggs for use at a later date increases the potential of nauplii to be used as a commercial food source. There are two types of eggs produced by copepods: diapause and non-diapause (or subitaneous). However, little is known about...
Show moreMariculture of fish is needed to support our ever growing global population. Copepods are a natural and beneficial source of first feed for many marine fish species, but it can be difficult to hatch enough when the fish are ready to feed. Therefore, storage of copepod eggs for use at a later date increases the potential of nauplii to be used as a commercial food source. There are two types of eggs produced by copepods: diapause and non-diapause (or subitaneous). However, little is known about diapause or the effects and duration of storage, either under cold or warm temperature conditions, on the biochemical composition of nauplii. Little is also known about the development of embryos that enter diapause. Diapause requires a refractory period before development of the embryo continues. The refractory period can last for several months regardless of environmental conditions. I studied the effects of both cold storage and cold storage with the addition of antibiotics on non-diapause eggs of the copepod Acartia tonsa and duration of storage for diapause eggs produced by Centropages hamatus and compared those results to nauplii derived from non-diapause eggs. The organic components analyzed to determine if potential changes were occurring during storage were lipids, fatty acids, proteins, free amino acids, and carbohydrates as well as the percent hatch of the eggs and the dry weight of the resultant nauplii. To understand diapause, we utilized two stains, one to determine the number of nuclei present and another to determine intracellular pH of the diapausing eggs. Acartia tonsa eggs stored for up to15 days at 1°C did not indicate any change in the biochemical make-up of the resulting nauplii. The only change we observed was in the viability of the eggs, which decreased at a steady rate over time. The viability of the eggs quickly approached zero percent hatch beyond 15 days. The addition of the antibiotic oxytetracyclin at a 10% concentration did not change the naupliar biochemistry and did not increase viability over the storage time. Centropages hamatus eggs maintained a high level of viability over the course of 13 months of storage under anoxic conditions. The nauplii derived from the diapause eggs stored at 25°C had similar biochemical components regardless of the length of the storage period. My study indicates that storage of A. tonsa and C. hamatus may not affect the nutritional value of the nauplii for aquaculture purposes. We also determined that the embryos of C. hamatus stopped developing after ~7 cleavages. The diapausing embryos also maintained an intracellular pH similar to the surrounding water and acidified when beginning to develop. This is the first time the intracellular pH and only the third time the nuclei of a copepod diapausing egg has been determined. This information could allow future researchers to interrupt diapause and induce the eggs to hatch before the end of the refractory period.
Show less
Date Issued: 2008
Identifier: FSU_migr_etd-0283
Format: Thesis

Title: Trends in Maximum and Minimum Temperature Deciles in Select Regions of the United States.
Creator: Smith, Rebecca Anne, O'Brien, James J., Bourassa, Mark A., Ruscher, Paul H., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Daily maximum and minimum temperature data from 758 COOP stations in nineteen states are used to create temperature decile maps. All stations used contain records from 1948 through 2004 and could not be missing more than 5 consecutive years of data. Missing data are replaced using a multiple linear regression technique from surrounding stations. For each station, the maximum and minimum temperatures are first sorted in ascending order for every two years (to reduce annual variability) and...
Show moreDaily maximum and minimum temperature data from 758 COOP stations in nineteen states are used to create temperature decile maps. All stations used contain records from 1948 through 2004 and could not be missing more than 5 consecutive years of data. Missing data are replaced using a multiple linear regression technique from surrounding stations. For each station, the maximum and minimum temperatures are first sorted in ascending order for every two years (to reduce annual variability) and divided into ten equal parts (or deciles). The first decile represents the coldest temperatures, and the last decile contains the warmest temperatures. Patterns and trends in these deciles can be examined for the 57-year period. A linear least-squares regression method is used to calculate best-fit lines for each decile to determine the long-term trends at each station. Significant warming or cooling is determined using the Student's t-test, and bootstrapping the decile data will further examine the validity of significance. Two stations are closely examined. Apalachicola, Florida shows significant warming in its maximum deciles and significant cooling in its minimum deciles. The maximum deciles seem to be affected by some localized change. The minimum deciles are discontinuous, and the trends are a result of a minor station move. Columbus, Georgia has experienced significant warming in its minimum deciles, and this appears to be the result of an urban heat-island effect. The discontinuities seen in the Apalachicola case study illustrate the need for a quality control method. This method will eliminate stations from the regional analysis that experience large changes in the ten-year standard deviations within their time series. The regional analysis shows that most of the region is dominated by significant cooling in the maximum deciles and significant warming in the minimum deciles, with more variability in the lower deciles. Field significance testing is performed on subregions (based on USGS 2000 land cover data) and supports the findings from the regional analysis; it also isolates regions, such as the Florida peninsula and the Maryland/Delaware region, that appear to be affected by more local forcings.
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0357
Format: Thesis

Title: Assimilation of GPS Radio Occultation Observations.
Creator: Shao, Hui, Zou, Xiaolei, Navon, Ionel M., Liu, Guosheng, Ray, Peter S., Krishnamurti, T. N., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Unlike conventional and satellite observations, the Global Positioning System (GPS) radio occultation (RO) techniques provide all-weather, high-vertical-resolution observations that require no calibration. In this dissertation, the assimilation of GPS RO data is studied using the National Centers for Environmental prediction (NCEP) three dimensional variational analysis system. Three GPS data assimilation choices are considered and compared. A set of GPS bending angle assimilation (BA)...
Show moreUnlike conventional and satellite observations, the Global Positioning System (GPS) radio occultation (RO) techniques provide all-weather, high-vertical-resolution observations that require no calibration. In this dissertation, the assimilation of GPS RO data is studied using the National Centers for Environmental prediction (NCEP) three dimensional variational analysis system. Three GPS data assimilation choices are considered and compared. A set of GPS bending angle assimilation (BA) experiments is first carried out and sensitivity of BA results to the observational weighting, the quality of the background fields, the variation of the gravity, and the vertical resolution of the GPS data are investigated. The GPS local refractivity assimilation (REF) is then conducted and compared with BA. Although REF is computationally cheaper than BA, the bias and root mean square errors of the background fields are more significantly reduced by BA than REF. Differences between GPS refractivity and bending angle assimilations are larger in thick-layered cloud systems (e.g., convective clouds in the mid-latitudes and cumulus clouds in the tropics) than in thin clouds and clear sky, which are found to be associated with the strength of horizontal gradient of the atmospheric refractivity. Aiming at achieving both accuracy and computational efficiency, a new observation operator that simulates the GPS excess phase delay is proposed and tested for GPS RO data assimilation. Using the excess phase delay, the along-track refractivity and refractivity gradient information can be included while the computational cost is kept low. Numerical results from the forward simulation and data assimilation using the excess phase delay (PHA) are compared with those of REF. PHA tends to produce a warmer and wetter model atmosphere, with finer structures and larger radii of influence than REF. Compared to GPS observations, simulations and analyses produced by PHA are more accurate than those of REF. It is also pointed out that under the assumption of the spherical symmetry of the local refractivity, the observation operator for the excess phase delay simplifies into a point scheme in which only a vertical profile of model refractivity is required.
Show less
Date Issued: 2005
Identifier: FSU_migr_etd-0301
Format: Thesis

Title: Evaluating the Aerosol First Indirect Effect Using Satellite Data.
Creator: Shao, Hongfei, Liu, Guosheng, Song, Kai-Sheng, Ellingson, Robert G., Fuelberg, Henry, Kim, Kwang-Yul, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: First proposed by Twomey, the aerosol first indirect effect hypothesizes that increased aerosol concentration leads to a larger number of cloud condensation nuclei, and therefore smaller but more numerous cloud droplets, which results in greater reflection of incoming solar radiation. It is known that this phenomenon has a net effect to cool the Earth radiatively and offset a substantial amount of the warming caused by the increasing of greenhouse gases. However, the magnitude of this effect...
Show moreFirst proposed by Twomey, the aerosol first indirect effect hypothesizes that increased aerosol concentration leads to a larger number of cloud condensation nuclei, and therefore smaller but more numerous cloud droplets, which results in greater reflection of incoming solar radiation. It is known that this phenomenon has a net effect to cool the Earth radiatively and offset a substantial amount of the warming caused by the increasing of greenhouse gases. However, the magnitude of this effect has been very uncertain. For example, discrepancies of more than a factor of 2 have been reported among various observational results. This uncertainty is a major hurdle in advancing our understanding of how humans have altered, and may in the future alter the Earth's climate. One of the difficulties in deriving the magnitude of this effect from observational data arises from the fact that the aerosol abundance often varies coherently with meteorological conditions, which makes it extremely hard to distinguish between the changes in cloud microphysical parameters caused by varying aerosol concentration and by varying meteorological conditions. Therefore, the goal of this study is to find a reliable method to extract the real strength and to narrow the uncertainty in the estimates of the indirect radiative effect of aerosols. To achieve this goal, first, a satellite visible/near-infrared algorithm is developed to retrieve cloud optical depth and effective radius simultaneously at solar wavelengths (0.63 and 1.61 mm), and a satellite microwave algorithm is developed to retrieve liquid water path in the microwave range (19 and 37 GHz). Using these algorithm we derive cloud microphysical variables in relation to the aerosol first indirect effect. Second, a drizzle index is introduced to discriminate the drizzle clouds from non-drizzle clouds from satellite, which ensures our estimation of the first indirect effect not being contaminated by precipitation related processes. Third, using an analytical model, we have explained how the coherent nature between cloud depth and aerosol concentration as observed in the northeastern Pacific causes misidentification of the aerosol first indirect effect. Finally, we have further explained that the coherent variation between aerosol abundance and meteorological conditions is the major cause responsible for the large discrepancies among various observed values of the aerosol first indirect effect published in literature. We found that clouds in clean areas tend to deviate more from adiabatic process than clouds in polluted area near the coast, which causes an artifact term in commonly-used methods for deriving the aerosol first indirect effect. By introducing a new method capable of removing this artifact, the real strength of the aerosol first indirect effect is assessed over the region of Northeast Pacific. It shows that the magnitude of the aerosol first indirect effect measured by the new parameter is about half of that originally estimated by Twomey
Show less
Date Issued: 2006
Identifier: FSU_migr_etd-0302
Format: Thesis

Title: Lightning Observations during Tropical Cyclone Intensity Change: A Composite Study of Spatial and Temporal Relationships.
Creator: Austin, Marcus, Fuelberg, Henry, Hart, Robert, Ruscher, Paul, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Although tropical cyclone (TC) track forecasts have improved considerably in recent years, predicting their intensity continues to be a challenge for both meteorologists and numerical models. A storm's path is primarily influenced greatly by large-scale atmospheric circulations; however, its strength appears to be dominated both by large scale influences and small-scale mechanisms within the storm itself. Most previous research on TC intensity change has employed either numerical modeling or...
Show moreAlthough tropical cyclone (TC) track forecasts have improved considerably in recent years, predicting their intensity continues to be a challenge for both meteorologists and numerical models. A storm's path is primarily influenced greatly by large-scale atmospheric circulations; however, its strength appears to be dominated both by large scale influences and small-scale mechanisms within the storm itself. Most previous research on TC intensity change has employed either numerical modeling or diagnostic approaches using traditional meteorological parameters. Only recently have studies begun to examine electrification as a means for assessing the potential for intensification. Several papers have considered lightning as a proxy for storm intensification, mostly using data from Vaisala's National Lightning Detection Network (NLDN) and Long-Range Lightning Detection Network (LLDN). However, they mostly have examined individual TCs. This study uses LLDN data to study 45 Atlantic Basin TCs between the years 2004 and 2008. Using the National Hurricane Center's (NHC) best track dataset, lightning data are collected for each TC out to a 500 km radius. Parameters including storm intensity, intensity change, environmental vertical wind shear, storm motion, and flash count are compiled at each NHC best track position. The data at each position then are categorized in several ways, including change in intensity. These methods allow us to examine relations between composites of storm intensity/intensification and convective distribution and frequency. Distributions of cloud-to-ground (CG) flash density with respect to storm motion and speed show that lightning generally is preferred in the TCs' right front and right rear quadrants. Hurricanes produce the greatest flash densities during relatively slow forward motion, while tropical depressions and tropical storms exhibit greater flash densities during faster forward motion. Storm-relative CG flash distributions during weakening, no pressure change, and slow intensification (-5 to 0 hPa 6 h-1) exhibit the same right front and rear quadrant preference as the TC intensity categories. Flash densities are greatest during periods of faster intensification, with a nearly symmetric presentation in the inner core region. When computing flash densities with respect to environmental deep layer wind shear, TCs exhibit a strong preference for lightning in the downshear left and right quadrants of the inner core (0-100 km) and outer rainbands (100-300 km), respectively. Tropical storms and hurricanes best show this relation, with TDs exhibiting a stronger preference for lightning in the downshear right quadrant. Relatively weak wind shear produces greater flash densities in all TC intensity categories. Conversely, storms experiencing strong shear exhibit smaller flash densities in all TC categories due to the disruption of deep convection. During periods of faster intensification, maximum flash densities are located in the inner core, with weakening, no change, and slow intensification periods containing greatest density in the outer rainbands. Average flash rates and flash densities are found to be greatest for weaker TCs (tropical depressions and tropical storms) with smaller flash rates and densities in hurricanes. Considering intensity change, periods of faster intensification exhibit significantly greater flash rates than periods of weakening, no pressure change, and slow intensification. Only weak relations are found between flash rates and intensity change, with the strongest relationship occurring when lightning lags (occurs after) the pressure change period. Lightning preceding (occurring before) the pressure change period exhibits the weakest relationships in all TC intensities. Correlations between CG lightning and sustained wind speed indicate that there is no preferred timing between maximum lightning activity and maximum sustained winds. Instead, maximum correlations occur during periods when greatest lightning activity both precedes and lags the maximum sustained wind. These results indicate that lightning is poorly correlated with intensity change and can be regarded as a poor choice for intensity forecasting.
Show less
Date Issued: 2011
Identifier: FSU_migr_etd-0261
Format: Thesis

Title: Abundance of Bottlenose Dolphins (Tursiops Truncatus) in the Big Bend of Florida, St. Vincent Sound to Alligator Harbor.
Creator: Tyson, Reny Blue, Nowacek, Douglas, Dewar, William, Wells, Randy, Chanton, Jeffrey, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Mark-recapture surveys implementing photographic identification techniques were used to estimate the abundance of bottlenose dolphins in an area of the Big Bend of Florida, stretching from St. Vincent Sound to Alligator Harbor, in the summer of 2007 and winter of 2008. The current population size of individuals in this region is unknown as the most recent abundance estimates were calculated based on aerial surveys conducted in 1993. Recent large scale mortality events, together with an...
Show moreMark-recapture surveys implementing photographic identification techniques were used to estimate the abundance of bottlenose dolphins in an area of the Big Bend of Florida, stretching from St. Vincent Sound to Alligator Harbor, in the summer of 2007 and winter of 2008. The current population size of individuals in this region is unknown as the most recent abundance estimates were calculated based on aerial surveys conducted in 1993. Recent large scale mortality events, together with an increasing potential for human impacts in this area, warrant an updated and increased understanding of the abundance and stock structure of dolphins in this region. Because the region is large and recent work here suggests that at least two distinct communities exist in these waters, the region was divided into the two areas in which these communities appear to reside (St. Vincent Sound/Apalachicola Bay and St. George Sound/Alligator Harbor) and independent estimates of abundance were calculated for each area and each season. Closed-population models in the program CAPTURE were used to derive the estimates of abundance and the assumptions underlying each model were examined. The estimates calculated from the models selected as being the most appropriate for each data set were similar for each survey area for each season: in the St. Vincent Sound/Apalachicola Bay survey area 182 ± 58 animals inhabited the survey area in the summer and 178 ± 77 animals in the winter; in the St. George Sound/Alligator Harbor survey area 365 ± 164 animals inhabited the survey area in the summer and 359 ± 87 animals in the winter. Results from this study also provided further evidence that at least two communities reside in these waters as only 2.4% of animals captured during the study were captured in both survey areas. If indeed two communities exist in these waters, it appears that site-fidelity and/or residence patterns of individuals may differ between them; in the St. Vincent Sound/Apalachicola Bay survey area 49.6% of the total animals captured were captured more than once and 29.6% were captured both seasons, while in the St. George Sound/Alligator Harbor survey area 35.3% were captured more than once and 13.8% of animals were captured both seasons. In addition, it appears that the St. George Sound/Alligator Harbor survey area supports a greater number of transient animals than the St. Vincent Sound/Apalachicola survey area (46.1% of distinctive animals were seen only once versus 29.9% respectively). This may be due in part to this survey area being more accessible to the open waters of the Gulf of Mexico than the St. Vincent Sound/Apalachicola Bay survey area, which is more protected by barrier islands. The results provided here can be used by the National Marine Fisheries Service to aid in their stock-assessment process and help in the management of the animals in this region.
Show less
Date Issued: 2008
Identifier: FSU_migr_etd-0323
Format: Thesis

Title: A Validation of the FSU/COAPS Climate Model.
Creator: Engelman, Mary Beth, O'Brien, James J., Ahlquist, Jon E., Ruscher, Paul H., LaRow, Timothy E., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: This study examines the predictability of the Florida State University/Center for Oceanic and Atmospheric Prediction Studies (FSU/COAPS) climate model, and is motivated by the model's potential use in crop modeling. The study also compares real-time ensemble runs (created using persisted SST anomalies) to hindcast ensemble runs (created using weekly updated SST) to asses the effect of SST anomalies on forecast error. Wintertime (DJF, 2 month lead time) surface temperature and precipitation...
Show moreThis study examines the predictability of the Florida State University/Center for Oceanic and Atmospheric Prediction Studies (FSU/COAPS) climate model, and is motivated by the model's potential use in crop modeling. The study also compares real-time ensemble runs (created using persisted SST anomalies) to hindcast ensemble runs (created using weekly updated SST) to asses the effect of SST anomalies on forecast error. Wintertime (DJF, 2 month lead time) surface temperature and precipitation forecasts over the southeastern United States (Georgia, Alabama, and Florida) are evaluated because of the documented links between tropical Pacific SST anomalies and climate in the southeastern United States during the winter season. The global spectral model (GSM) runs at a T63 resolution and then is dynamically downscaled to a 20 x 20 km grid over the southeastern United States using the FSU regional spectral model (RSM). Seasonal, monthly, and daily events from the October 2004 and 2005 model runs are assessed. Seasonal (DJF) plots of real-time forecasts indicate the model is capable of predicting wintertime maximum and minimum temperatures over the southeastern United States. The October 2004 and 2005 real-time model runs both produce temperature forecasts with anomaly errors below 3°C, correlations close to one, and standard deviations similar to observations. Real-time precipitation forecasts are inconsistent. Error in the percent of normal precipitation vary from greater than 100% in the 2004/2005 forecasts to less than 35% error in the 2005/2006 forecasts. Comparing hindcast runs to real-time runs reveals some skill is lost in precipitation forecasts when using a method of SST anomaly persistence if the SST anomalies in the equatorial Pacific change early in the forecast period, as they did for the October 2004 model runs. Further analysis involving monthly and daily model data as well as Brier scores (BS), relative operating characteristics (ROC), and equitable threat scores (ETS), are also examined to confirm these results.
Show less
Date Issued: 2008
Identifier: FSU_migr_etd-0560
Format: Thesis

Title: Determination of the Quantity of Cloud Liquid in Snow Clouds and Its Effect on Masking the Snow Scattering Signature.
Creator: Smith, John Robert, Liu, Guosheng, Bourassa, Mark, Fuelberg, Henry, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Many studies have been conducted on the satellite remote sensing of rainfall, but not on the remote sensing of snowfall. To obtain a global view of snowfall in a timely matter, passive high frequency microwave satellite measurements must be used. Therefore, an accurate algorithm for detecting and retrieving snowfall on a global scale is needed. In developing this algorithm, it is important to account for the snow scattering signature which reduces the upwelling emission signal from the ocean...
Show moreMany studies have been conducted on the satellite remote sensing of rainfall, but not on the remote sensing of snowfall. To obtain a global view of snowfall in a timely matter, passive high frequency microwave satellite measurements must be used. Therefore, an accurate algorithm for detecting and retrieving snowfall on a global scale is needed. In developing this algorithm, it is important to account for the snow scattering signature which reduces the upwelling emission signal from the ocean surface observed at the top of the atmosphere. However, the emission due to cloud liquid will increase the upwelling radiation, therefore masking the snow scattering signature. Thus, cloud liquid within snow clouds must be understood. In this study, data from the Cloud Profiling Radar on CloudSat and AMSR-E on Aqua are used to investigate the quantity of cloud liquid for snowfall events. The relationship between cloud liquid and echo top, cloud thickness, and two-meter air temperature is determined. The quantity of cloud liquid present in stratiform and convective snowfall events is also compared. Using snowfall profiles obtained from the reflectivity profiles provided by CloudSat, the masking effect of cloud liquid on the snow scattering signature on vertical and horizontal brightness temperature is determined for snow events with various surface snowfall rates. The masking effect on a parameter designed to reduce the emission signal due to cloud liquid, the polarization corrected temperature, is also tested.
Show less
Date Issued: 2010
Identifier: FSU_migr_etd-0369
Format: Thesis

Title: Surface Heating and Restratification of the Ocean after a Tropical Cyclone.
Creator: Deal, Robert, Clayson, Carol Anne, Hart, Robert, Ruscher, Paul, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Ocean transport of heat is a substantial component of the climate system but its characteristics and dynamic causes are still somewhat unknown. Prior research has shown that global observations from the ocean and atmosphere indicate that the ocean and atmosphere transport about 6 PW of energy from the equatorial regions towards the poles. Studies have shown that approximately 2 PW of that transport are carried by the ocean. It has been proposed that global tropical cyclone activity could...
Show moreOcean transport of heat is a substantial component of the climate system but its characteristics and dynamic causes are still somewhat unknown. Prior research has shown that global observations from the ocean and atmosphere indicate that the ocean and atmosphere transport about 6 PW of energy from the equatorial regions towards the poles. Studies have shown that approximately 2 PW of that transport are carried by the ocean. It has been proposed that global tropical cyclone activity could account for a large amount of the mixing needed to explain the thermohaline circulation driving this transport. However, there remain insufficient observations to conclusively prove this hypothesis. After a tropical cyclone moves across the ocean it leaves behind a wake of colder temperatures in the upper ocean. The cold wake is primarily caused by mixing, upwelling and an enthalpy flux into the atmosphere. This study makes use of the JASON-1, and TOPEX/POSEIDON satellite altimeters to investigate the amount of heating of the ocean required to re-stratify the ocean to pre storm conditions. Argo floats are also used to validate results found from the sea surface height anomalies from satellite. In order to attain the necessary spatial and temporal resolution, the Climate System Forecast Reanalysis (CFSR) model is used. Given that CFSR is a coupled atmospheric and ocean model, it enabled this study to compare the modeled storms and then the impact of storms on the ocean. After the storm passed through the area, surface heating fluxes could be determined over the duration of the storm thus providing a direct comparison of heat loss and net heat gain over the entire duration of the storm. It was found that during the time period of the cold wake, the surface heating imbalance was high enough to account for all of the rewarming of the cold wake. Therefore it is possible that global cyclone activity could account for the large amount of mixing required to explain the thermohaline circulation.
Show less
Date Issued: 2011
Identifier: FSU_migr_etd-0060
Format: Thesis

Title: Determining the Error Characteristics of H*WIND.
Creator: Dinapoli, Steven, Bourassa, Mark, Powell, Mark, Hart, Robert, Liu, Guosheng, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: The HRD Real-time Hurricane Wind Analysis System (H*Wind) is a software application used by NOAA's Hurricane Research Division to create a gridded tropical cyclone wind analysis based on a wide range of observations. One application of H*Wind fields is calibration of scatterometers for high wind speed environments. Unfortunately, the accuracy of the H*Wind product has not been studied extensively, and therefore the accuracy of scatterometer calibrations in these environments is also unknown....
Show moreThe HRD Real-time Hurricane Wind Analysis System (H*Wind) is a software application used by NOAA's Hurricane Research Division to create a gridded tropical cyclone wind analysis based on a wide range of observations. One application of H*Wind fields is calibration of scatterometers for high wind speed environments. Unfortunately, the accuracy of the H*Wind product has not been studied extensively, and therefore the accuracy of scatterometer calibrations in these environments is also unknown. This investigation seeks to determine the uncertainty in the H*Wind product and estimate the contributions of several potential error sources. These error sources include random observation errors, relative bias between different data types, temporal drift resulting from combining non-simultaneous measurements, and smoothing and interpolation errors in the H*Wind software. The effects of relative bias between different data types and random observation errors are determined by performing statistical calculations on the observed wind speeds. We show that in the absence of large biases, the total contribution of all error sources results in an uncertainty of approximately 7% near the storm center, which increases to nearly 15% near the tropical storm force wind radius. The H*Wind analysis algorithm is found to introduce a positive bias to the wind speeds near the storm center, where the analyzed wind speeds are enhanced to match the highest observations. In addition, spectral analyses are performed to ensure that the filter wavelength of the final analysis product matches user specifications. With increased knowledge of these error sources and their effects, researchers will have a better understanding of the uncertainty in the H*Wind product, and can then judge the suitability of H*Wind for various research applications
Show less
Date Issued: 2010
Identifier: FSU_migr_etd-0090
Format: Thesis

Title: Development of the Coamps Adjoint Mesoscale Modeling System for Assimilating Microwave Radiances within Hurricanes.
Creator: Amerault, Clark Mathew, Zou, Xiaolei, Navon, Ionel Michael, O'Brien, James J., Liu, Guosheng, Krishnamurti, T.N., Department of Earth, Ocean and Atmospheric Sciences, Florida...
Show moreAmerault, Clark Mathew, Zou, Xiaolei, Navon, Ionel Michael, O'Brien, James J., Liu, Guosheng, Krishnamurti, T.N., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: An adjoint mesoscale modeling system based on the Naval Research Laboratory's Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS) atmospheric model was created for use in sensitivity and data assimilation experiments. In addition to the tangent linear and adjoint models of the dynamical core of the COAMPS model, the system includes the tangent linear and adjoint models of the boundary layer turbulent kinetic energy, cumulus, and explicit moist physics parameterizations. The...
Show moreAn adjoint mesoscale modeling system based on the Naval Research Laboratory's Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS) atmospheric model was created for use in sensitivity and data assimilation experiments. In addition to the tangent linear and adjoint models of the dynamical core of the COAMPS model, the system includes the tangent linear and adjoint models of the boundary layer turbulent kinetic energy, cumulus, and explicit moist physics parameterizations. The inclusion of these adjoint model physics schemes allows for assimilation experiments involving rain-affected observations such as microwave radiances. A radiative transfer model which includes the effects of hydrometeors on atmospheric radiation was linked to the adjoint modeling system to assimilate microwave radiance observations. Probability distribution functions of model-produced and SSM/I observed brightness temperatures show that the mesoscale prediction overestimates the areas of precipitation, but overall matches the microwave observations quite well. Furthermore, estimates of vertical background error covariance matrices for the hydrometeor variables were calculated using differences between model forecasts which utilized different explicit moisture schemes. The statistics of the differences between the forecasts were assumed to be the same as the statistics of the background error for these variables. The inverse of these matrices (which are needed for data assimilation) were computed using Singular Value Decomposition. Only the largest singular value was kept in calculating the inverse. This ensured that all of the elements of the inverse matrix were non-negative. Finally, microwave radiance observations for Hurricane Bonnie (1998) were assimilated in a 4-dimensional variational data assimilation framework using the COAMPS adjoint model. The model-produced radiances calculated from the analysis fields after the assimilation process match the observations well for the lower frequency channels which are sensitive to liquid precipitation and water vapor. In the highest frequency channel, where the presence of frozen hydrometeors can have a large impact on the radiance value, the match between the analysis and the observations was not as good. The forecasted hurricane was slightly stronger after the assimilation of microwave radiances in terms of both maximum surface windspeed and minimum central sea level pressure, and some improvement was seen in radiance space as well. More observations from within the hurricane, which will improve the analysis of other variables, will most likely be needed to see a greater forecast impact from the assimilation of these observations.
Show less
Date Issued: 2005
Identifier: FSU_migr_etd-0049
Format: Thesis

Title: Hurricane Surface Wind Model for Risk Management.
Creator: Axe, Lizabeth Marie, Krishnamurti, T. N., Ruscher, Paul H., Cunningham, Philip, Cocke, Steven, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: The landfalls of extreme hurricane events in recent years reveal the need for more accurate predictions of winds during landfalling tropical cyclone events to help reduce property damage. The goal of this study is to develop a high-resolution surface wind exposure model that incorporates an effective roughness model. In this study, the wind model calculates flight- level winds of a rankine- like vortex in a simple synthetic large-scale environment at a 1 km resolution. The flight-level winds...
Show moreThe landfalls of extreme hurricane events in recent years reveal the need for more accurate predictions of winds during landfalling tropical cyclone events to help reduce property damage. The goal of this study is to develop a high-resolution surface wind exposure model that incorporates an effective roughness model. In this study, the wind model calculates flight- level winds of a rankine- like vortex in a simple synthetic large-scale environment at a 1 km resolution. The flight-level winds are then reduced to 10 m using a reduction scheme based on GPS dropwindsonde profiles. The roughness component calculates the effective roughness length using a radial weight function based on the source area model developed by Schmid and Oke, with an upwind fetch of 5 km. The weight function is dependent on the distance from sensor, sensor height, surface roughness (approximately 100 m resolution), and the Monin-Obukov length. The weighted average of roughness values is taken over 8 possible wind directions to give a more sophisticated effective roughness length for all land points. The high-resolution wind exposure model provides realistic analyses for hurricane Andrew (1992), Erin (1995), Kate (1985), and Donna (1960) at the time of their Florida landfalls. It is also useful for recreating historical hurricane case studies. There is a potential for further development into a real-time analysis and forecasting tool during tropical cyclone landfall events.
Show less
Date Issued: 2003
Identifier: FSU_migr_etd-0039
Format: Thesis

Title: Post-Processing Improvements to an Ensemble Forecast Using an Archive of Past Forecasts and Verifications.
Creator: Allgood, Adam Douglas, Ahlquist, Jon E., Krishnamurti, T. N., Zou, Xiaolei, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Ensemble forecasts are the primary tool used operationally to assess forecast uncertainty. Studies of ensemble forecasts, however, have shown that forecast verifications too frequently lie outside of the ensemble's range of possibilities, meaning that uncorrected ensemble forecasts suggest more confidence than is justified. To make ensemble forecasts more representative of the actual range of possibilities, we present a technique to post-process ensemble forecasts by replacing member...
Show moreEnsemble forecasts are the primary tool used operationally to assess forecast uncertainty. Studies of ensemble forecasts, however, have shown that forecast verifications too frequently lie outside of the ensemble's range of possibilities, meaning that uncorrected ensemble forecasts suggest more confidence than is justified. To make ensemble forecasts more representative of the actual range of possibilities, we present a technique to post-process ensemble forecasts by replacing member forecasts with verifications of what actually occurred when past forecasts were similar. To maximize the information that can be extracted from an archive of past forecasts and verifications, we allow analogs to come from different locations in space. We evaluated our procedure to post-process NCEP ensemble precipitation forecasts for the United States for 15-day periods in July 2005 and January 2006. Our analog correction technique significantly improved the ensemble's ability to forecast the probability of precipitation, in particular correcting the NCEP Global Ensemble's ``wet' bias at low precipitation amounts. Brier Skill Scores for 6-hour accumulated precipitation during the winter indicated that uncorrected ensemble forecasts were less skillful at predicting the probability of precipitation than forecasting zero precipitation as indicated by negative Brier Skill Scores (roughly -2.5). Post processed forecasts had Brier Skill Scores as high as 0.34. The tendency of the ensemble to underforecast heavy precipitation events, however, was not well corrected by our post-processing technique. Examinations of analog locations during heavy precipitation events indicated that analogs were taken from regions where precipitation patterns differed from those at the forecast point. This indicates that analogs must be chosen using more information than merely the similarity of ensemble precipitation forecasts to past forecasts.
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0173
Format: Thesis

Title: Holocene Diatoms Recovered from Shaldril I Cores, Maxwell Bay, Antarctica.
Creator: Geary, Lindsey Eileen, Wise, Sherwood W., Georgen, Jennifer, Donoghue, Joseph F., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: High-resolution Holocene sediment cores from the continental shelf of Antarctica are integral to the study of recent climate transitions, but such records are rare. The inaugural SHALDRIL I cruise to Maxwell Bay along the Northern Antarctica Peninsula, however, recovered the most expanded record to date at Site NBP05-02-1B. More than twice as long as any other such Antarctic sequence, the 108.2 m section dates back 13,480 yr B.P. Presented here is a record of climate variation interpreted...
Show moreHigh-resolution Holocene sediment cores from the continental shelf of Antarctica are integral to the study of recent climate transitions, but such records are rare. The inaugural SHALDRIL I cruise to Maxwell Bay along the Northern Antarctica Peninsula, however, recovered the most expanded record to date at Site NBP05-02-1B. More than twice as long as any other such Antarctic sequence, the 108.2 m section dates back 13,480 yr B.P. Presented here is a record of climate variation interpreted from analyses of the diatom content. Diatoms have proven to be a useful tool in the study of paleoclimate. Analyses completed here include species diversity, total diatom abundance (valves per gram of sediment), Eucampia antarctica var. antarctica to E. antarctica var. recta ratio, Eucampia index, Chaetoceros resting-spore percent, Chaetoceros hyalochaete to C. vegetative ratio, and Thalassiosira antarctica T2 percentage. The analyses show a continuous sea-ice assemblage with minor fluctuations in response to changing sea-ice conditions. Other than the Thalassiosira antarctica T2 percentage, all analyses show a prominent warming period identified as the Mid-Holocene Climatic Optimum. Thalassiosira antarctica T2 percentage marks a period of deglaciation at approximately 11 ka. This episode of deglaciation has been documented in other studies and is believed to mark the onset of present-day ice conditions.
Show less
Date Issued: 2008
Identifier: FSU_migr_etd-0129
Format: Thesis

Title: Improving Hurricane Intensity Forecasts in a Mesoscale Model via Microphysical Parameterization Methods.
Creator: Albers, Cerese Marie, Krishnamurti, Tiruvalam N., Liu, Guosheng, Ruscher, Paul, Hood, Robbie, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Accurate hurricane intensity prediction is at the forefront of atmospheric science today, and improvements to mesoscale modeling of these storms continue to be major components of refining the accuracy of intensity forecasting. The primary goal of this study is to improve mesoscale modeling of hurricane intensity via the comparison of field campaign observations of Hurricane Erin 2001 from the Fourth Convection And Moisture Experiment (CAMEX-4) and Hurricane Dennis 2005 from the Tropical...
Show moreAccurate hurricane intensity prediction is at the forefront of atmospheric science today, and improvements to mesoscale modeling of these storms continue to be major components of refining the accuracy of intensity forecasting. The primary goal of this study is to improve mesoscale modeling of hurricane intensity via the comparison of field campaign observations of Hurricane Erin 2001 from the Fourth Convection And Moisture Experiment (CAMEX-4) and Hurricane Dennis 2005 from the Tropical Cloud Systems and Processes (TCSP) mission with simulated results of improved microphysical parameterization in a mesoscale model that utilizes the Krishnamurti, et al (1991) technique of rain rate initialization (RRI). Comparison of the simulated results with field observations collocated with satellite observations provides a way to validate many different aspects of the simulated hurricane's structure and intensity. The mesoscale model used in this research is the Weather Research & Forecasting (WRF) model version 2.1 (ARW). Much of the existing microphysical parameterization of this model is built from results of mid-latitude observations. Substantial improvement to the model's intensity forecasting in the tropics can be made via proper parameterization of the model microphysics for hurricanes. With a foundation of results from other hurricane mesoscale modeling initial/boundary conditions, dynamics and physics studies, basic options for modeling hurricanes Erin (2001) and Dennis (2005) are chosen and held constant during a series of microphysical sensitivity experiments for each storm. These are specifically designed to isolate the individual effects of altering one microphysical parameter at a time on the hurricane's intensity forecast and are carried out in a doubly or triply nested way. The initial and boundary conditions used in the innermost grid with finer resolution are obtained from the respective outermost grids where rain rate initialization is invoked. All of the results are illustrated for the highest-resolution innermost domain, which is integrated using an explicit microphysics scheme. Each of these experiments are integrated for a forty-eight hour forecast period, adequately capturing the mature and intensification stages of the two hurricanes. Skill scores are obtained from the results of the two sets of experiments. Root Mean Square Errors (RMSE) and Anomaly Correlations (AC) are computed by comparing the model output of each experiment to NCEP's final analysis (fnl) available at one-degree horizontal resolution and six-hour temporal resolution interpolated to the respective model grid. Taking into account the way that each experiment performs in terms of simulated storm intensity as well as optimized RMSE and AC, the optimal combination of microphysical processes (i.e. melting, evaporation, fall speed of hydrometeors) for each storm is determined. Then a final forty-eight hour forecast of each hurricane is made utilizing this optimal microphysical parameterization combination. The results from each final run are compared to observations, skill scores are computed, and the final intensity improvements for both hurricanes Erin and Dennis are shown. The results of this study strengthen the evidence that RRI and proper microphysical parameterization in mesoscale hurricane modeling are both useful and effective techniques, and combine to improve hurricane intensity forecasting in a mesoscale model.
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0156
Format: Thesis

Title: An Examination of the Differences in Tropical Cyclone Pressure-Wind Relationships Among Observations, Model Analyses, and Model Forecasts.
Creator: Visin, Lauren, Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: Despite significant advances in tropical cyclone (TC) track forecasting over the past few decades, intensity forecasts remain problematic, even for high-resolution computer models uniquely developed and tailored to TC prediction. This study examines the ability of two of these models, the Geophysical Fluid Dynamics Laboratory (GFDL) model and the Hurricane Weather Research and Forecasting (HWRF) model, to analyze and predict one measure of TC structure in the Atlantic Basin. Instead of more...
Show moreDespite significant advances in tropical cyclone (TC) track forecasting over the past few decades, intensity forecasts remain problematic, even for high-resolution computer models uniquely developed and tailored to TC prediction. This study examines the ability of two of these models, the Geophysical Fluid Dynamics Laboratory (GFDL) model and the Hurricane Weather Research and Forecasting (HWRF) model, to analyze and predict one measure of TC structure in the Atlantic Basin. Instead of more conventional evaluations based solely on a TC's maximum wind speed or minimum sea level pressure (MSLP), the relationship between these two variables is used: a TC's pressure-wind relationship (PWR), which gives a more detailed look at how well each model analyzes and forecasts TC structure. The analysis begins in 2007, the year the GFDL was initially "frozen" (development and improvements were ceased) and also the first year that the HWRF was used for operational forecasting. Comparison of both GFDL and HWRF analyses and forecasts to the National Hurricane Center's (NHC) "best track" (database of 6-hourly observations of vital statistics such as maximum wind speed and MSLP for all TCs) revealed that, while both models produced errors in their analyses and forecasts, the GFDL outperformed the HWRF in both analysis and forecasting of TC PWR's for Atlantic Basin hurricanes from 2007-2013.. There was a subsection of particularly strong TCs (maximum winds above 120kt, MSLP lower than 950mb) whose structure was forecast especially poorly. The forecast PWR's produced by the HWRF fell largely outside the "best track" for this set of intense TCs, suggesting that the structures produced by the HWRF are inconsistent with our best estimates of observations in the Atlantic Basin and given current climate conditions. The PWR distribution evolved considerably for the HWRF over time, presumably as model improvements were made (including a decrease in model gridspacing). This has led to the model analysis PWR becoming more consistent with the model forecast PWR envelope. Nonetheless, both often fall outside the best-track estimates of PWR and potential explanations for this disparity are presented.
Show less
Date Issued: 2014
Identifier: FSU_migr_uhm-0386
Format: Thesis

Title: Algorithms for Advanced Tropical Cyclone Visualization.
Creator: Winterbottom, Henry R., Zou, Xiaolei, Erlebacher, Gordon, Bourassa, Mark A., Liu, Gousheng, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: With the events of recent years - especially in the Atlantic tropical basin, the need for additional forecast tools to aid in tropical cyclone (TC) prediction and understanding is apparent. A suite of algorithms to be used for 3-D TC visualization are presented. Utilizing the assets of the Amira visualization software, we present methods which constitute a real-time visualization routine of TC genesis, mesoscale, and TC centered features derived from the The Florida State University (FSU)...
Show moreWith the events of recent years - especially in the Atlantic tropical basin, the need for additional forecast tools to aid in tropical cyclone (TC) prediction and understanding is apparent. A suite of algorithms to be used for 3-D TC visualization are presented. Utilizing the assets of the Amira visualization software, we present methods which constitute a real-time visualization routine of TC genesis, mesoscale, and TC centered features derived from the The Florida State University (FSU) adaptation of the Pennsylvania State University (PSU) and National Center for Atmospheric Research (NCAR) Fifth Generation Mesoscale Model (MM5). However, the algorithms we develop are generic in that they can be applied to any gridded output from a forecast model. A method for the removal TC vorticity fields allowing an approximation of the environmental steering levels is also developed. The development and use of an adaptive wavenumber refinement filter (AWRF) has proven to outperform various alternative methods for TC vortex removal and thus the preservation of the environmental flow. Case study inter-comparisons are performed and illustrate that the AWRF provides the smallest mean track errors in future forecast position compared to those determined by the model's use of minimum sea level pressure (SLP) and vorticity maxima algorithm for TC center location. Discussions are also provided suggesting areas of needed improvement within the algorithm as illustrated by the case studies presented.
Show less
Date Issued: 2006
Identifier: FSU_migr_etd-0929
Format: Thesis

Title: Characterization of Metal-Reducing Microbial Communities from Acidic Subsurface Sediments Contaminated with Uranium(VI).
Creator: Edwards, Ellen Mclain, Kostka, Joel E., Balkwill, David, Krumholz, Lee R., Burnett, Bill, Chanton, Jeff, Department of Earth, Ocean and Atmospheric Sciences, Florida State...
Show moreEdwards, Ellen Mclain, Kostka, Joel E., Balkwill, David, Krumholz, Lee R., Burnett, Bill, Chanton, Jeff, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: Extraction and processing of uranium ore during the Cold-War era have left many sites around the world contaminated with uranium. Leaching of uranium into the groundwater is of major concern because oxidized uranium, U(VI), is toxic, soluble, and therefore mobile in subsurface environments where the majority of contamination resides. Uranium [U(VI)] can be immobilized from water by its reduction from UO22+ to insoluble U(IV) oxide, and biostimulation by the addition of carbon substrates has...
Show moreExtraction and processing of uranium ore during the Cold-War era have left many sites around the world contaminated with uranium. Leaching of uranium into the groundwater is of major concern because oxidized uranium, U(VI), is toxic, soluble, and therefore mobile in subsurface environments where the majority of contamination resides. Uranium [U(VI)] can be immobilized from water by its reduction from UO22+ to insoluble U(IV) oxide, and biostimulation by the addition of carbon substrates has been shown to stimulate the microbial reduction of U(VI) in contaminated subsurface environments. However, in order to develop effective bioremediation strategies for contaminant metals, the microbial communities and mechanisms controlling metal reduction need to be better understood, especially in acidic subsurface environments. This dissertation research used an array of microbiological and geochemical techniques to examine metal reduction in materials from the U.S. Department of Energy (DOE) Natural and Accelerated Bioremediation Research (NABIR)'s Field Research Center (FRC), in Oak Ridge, Tennessee, where subsurface sediments are cocontaminated with high levels of U(VI) and nitrate. The combination of low pH and high concentrations of nitrate and radionuclides in an aerobic subsurface environment is representative of many sites within the U.S. nuclear weapons complex managed by the DOE. Thus, results are not only important for bioremediation research at the FRC but can also be applied to other sites. Iron(III)-reducing bacteria (FeRB) have been demonstrated to rapidly catalyze U(VI) reduction and Fe(III) is an abundant electron acceptor in uranium-contaminated subsurface sediments. Thus, FeRB communities were the focus of this dissertation. The abundance, diversity, and activity of indigenous metal-reducing microbial communities likely to contribute to uranium reduction was examined in the field and under more controlled conditions in the laboratory. In chapter one, a combination of cultivation-dependent and cultivation-independent microbiological techniques were utilized to characterize metal-reducing bacteria in FRC subsurface sediments. Iron(III)-reducing enrichment cultures were initiated from pristine and contaminated (high in uranium, nitrate; low pH) subsurface sediments at pH 7 and pH (4-5). In selected enrichments, nitrate contamination was removed from the sediment by washing. Using a most probable number (MPN) approach and a range of different carbon sources (glycerol, acetate, lactate, or glucose), sediments of lower pH typically yielded lower counts of FeRB except when glucose was utilized as an electron donor in acidic enrichments. Phylogenetic analysis of the 16S rRNA gene sequences extracted from the highest positive MPN dilutions revealed that the predominant members of Fe(III)-reducing consortia cultured from pristine background sediments were closely related to the family Geobacteraceae, whereas a recently characterized Fe(III)-reducer (Anaeromyxobacter) and organisms not previously shown to reduce Fe(III) (Paenibacillus, Brevibacillus) predominated the Fe(III)-reducing consortia of contaminated sediments. Analysis of enrichment cultures using terminal restriction fragment length polymorphism (T-RFLP) strongly supported the cloning and sequencing results. Enrichment cultures of Fe(III)-reducers from contaminated sites were also shown to rapidly reduce millimolar amounts of U(VI) in comparison to killed controls. Using DNA extracted directly from the subsurface sediments, quantitative analysis of 16S rRNA gene sequences with MPN-PCR indicated that Geobacteraceae sequences were one to two orders of magnitude less abundant in contaminated as compared to pristine environments. In contrast, Anaeromyxobacter sequences were more abundant in contaminated sediments. Thus, results from a combination of cultivation-based and cultivation-independent approaches indicate that the abundance/ community composition of Fe(III)-reducing consortia in subsurface sediments is dependent upon geochemical parameters (pH, nitrate concentration) and microorganisms capable of producing spores (gram positives) or spore-like bodies (Anaeromyxobacter) were representative of acidic subsurface environments. In chapter two, microbial communities were studied in sediment microcosms under near in situ conditions in order to establish rates of respiration and to assess which environmental parameters might be governing activity. Rates of nitrate reduction, metal reduction, and electron donor utilization were measured in acidic subsurface sediments across a range of environmental variables (pH, nitrate) relevant to bioremediation. Microbial activity was minimal at pH 5 or below and in the absence of added electron donor, indicating that acidity is a master variable controlling microbial metabolism in FRC sediments, while high nitrate concentrations were not found to be toxic to microorganisms. In microcosms of neutral pH sediment and neutralized acidic sediment, similar, rapid rates of terminal-electron-accepting pathways were observed. The pathways of nitrate reduction were dictated by sediment pH, as denitrification predominated in glucose-amended sediments originating from neutral pH zones, whereas in neutralized acidic microcosms, metabolism shifted to dissimilatory nitrate reduction (to ammonium). Electron donors were determined to stimulate microbial metabolism leading to metal reduction in the following order: glucose > ethanol > lactate > hydrogen. A mass balance of carbon equivalents was obtained in glucose- and ethanol-amended microcosms. In neutralized acidic sediments amended with glucose, 50 to 60 % of carbon equivalents were recovered as fermentation products (mainly as acetate) and glucose-amended microcosms showed the highest iron reduction activity, while the extended presence of ethanol seemed to hinder iron reduction. The presence of bicarbonate greatly increased both nitrate and iron reduction activity in glucose-amended microcosms, more so than raising the pH by washing. Washing did increase iron reduction in glucose-amended microcosms as compared to neutralized acidic sediments, indicating that soluble toxins may somehow decrease iron reduction potential. ethanol > lactate > hydrogen. A mass balance of carbon equivalents was obtained in glucose- and ethanol-amended microcosms. In neutralized acidic sediments amended with glucose, 50 to 60 % of carbon equivalents were recovered as fermentation products (mainly as acetate) and glucose-amended microcosms showed the highest iron reduction activity, while the extended presence of ethanol seemed to hinder iron reduction. The presence of bicarbonate greatly increased both nitrate and iron reduction activity in glucose-amended microcosms, more so than raising the pH by washing. Washing did increase iron reduction in glucose-amended microcosms as compared to neutralized acidic sediments, indicating that soluble toxins may somehow decrease iron reduction potential. lactate > hydrogen. A mass balance of carbon equivalents was obtained in glucose- and ethanol-amended microcosms. In neutralized acidic sediments amended with glucose, 50 to 60 % of carbon equivalents were recovered as fermentation products (mainly as acetate) and glucose-amended microcosms showed the highest iron reduction activity, while the extended presence of ethanol seemed to hinder iron reduction. The presence of bicarbonate greatly increased both nitrate and iron reduction activity in glucose-amended microcosms, more so than raising the pH by washing. Washing did increase iron reduction in glucose-amended microcosms as compared to neutralized acidic sediments, indicating that soluble toxins may somehow decrease iron reduction potential. hydrogen. A mass balance of carbon equivalents was obtained in glucose- and ethanol-amended microcosms. In neutralized acidic sediments amended with glucose, 50 to 60 % of carbon equivalents were recovered as fermentation products (mainly as acetate) and glucose-amended microcosms showed the highest iron reduction activity, while the extended presence of ethanol seemed to hinder iron reduction. The presence of bicarbonate greatly increased both nitrate and iron reduction activity in glucose-amended microcosms, more so than raising the pH by washing. Washing did increase iron reduction in glucose-amended microcosms as compared to neutralized acidic sediments, indicating that soluble toxins may somehow decrease iron reduction potential. For the first time, rates of metal reduction and electron donor utilization were measured in acidic subsurface sediments across a range of environmental variables (pH, nitrate) relevant to bioremediation. In concurrence with previous studies of neutrophilic uranium-contaminated subsurface environments, metal reduction in the acidic subsurface did not occur until after nitrate was depleted to low levels in response to pH neutralization and carbon substrate addition. Through quantification of the rates and pathways of terminal-electron-accepting pathways in acidic subsurface sediments, we provide important inputs for reaction-based biogeochemical models that will greatly aid in the development of in situ radionuclide remediation strategies. In chapter 3, a pure culture of Fe(III)-reducing bacteria isolated from the FRC subsurface was further examined for its ability to reduce U(VI). Uranium measurements were conducted using a Kinetic Phosphorescence Analyzer, which was cross-calibrated using alpha spectrometry. The uranium reduction ability of isolate FRC32, was compared to a known uranium-reducing organism, Geobacter metallireducens. FRC32 was tested under various cultivation conditions, including a range of uranium and cell concentrations and up to 90% of 0.1-5 mM uranium was reduced. However, reduction in killed-control cultures suggests either a strong potential for abiotic reduction or the ability to form spores. Thus, the potential for uranium reduction was observed, but further research is necessary to determine which environmental parameters are controlling uranium transformation by this organism.
Show less
Date Issued: 2005
Identifier: FSU_migr_etd-0599
Format: Thesis

Title: The Development of Forecast Confidence Measures Using NCEP Ensembles.
Creator: Durante, Andrew Vincent, Hart, Robert, Fuelberg, Henry, Krishnamurti, T.N., Watson, Andrew I., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Ensemble model data can provide a wealth of guidance to forecasters, especially in terms of forecast confidence. A model run where members diverge generally corresponds to a low confidence forecast, while a model run where members converge generally corresponds to a forecast of high confidence. The current NWS graphically based forecasts accessible to the public do not show this measure of uncertainty and thus communicate a false sense of confidence or precision. From August 2004 into 2006,...
Show moreEnsemble model data can provide a wealth of guidance to forecasters, especially in terms of forecast confidence. A model run where members diverge generally corresponds to a low confidence forecast, while a model run where members converge generally corresponds to a forecast of high confidence. The current NWS graphically based forecasts accessible to the public do not show this measure of uncertainty and thus communicate a false sense of confidence or precision. From August 2004 into 2006, approximately 2 years of individual GFS model ensemble data were analyzed. The result is a climatology of each ensemble member, which obviously does not match the observed climatology based on the NCEP reanalysis. The GFS model ensemble climatology was normalized so that there is a mapping between the current model ensemble value and the climatological value. Since there is only two years of data, the climatology is calculated on a 45 day temporal window. This method is similar, but more simplistic, to the method that is used in the FSU Superensemble (Krishnamurti 2000) of using temporal windows to increase climatology robustness in the training dataset. The variables analyzed here include 2-m temperature, 10-m wind speed and 10-m vorticity. Normalized climatology distributions have been calculated for each grid point within the ensemble member, with forecast confidence measures developed by comparing the normalized spread of the ensemble members to the model climatological spread, as described below. This normalized spread is compared to the typical spread for that time of year, location, and forecast length to arrive at a relative measure of forecast uncertainty. If the current model uncertainty is greater (less) than the uncertainty of the model climatology, then there is a lower (higher) than average confidence. Confidence graphics have been developed and analyses to see how confidence values behave with certain synoptic situations are ongoing. This overall behavior along with certain case studies will be featured. It has also been seen that there is a statistical significant difference in NWS forecast error between low confidence and high confidence regimes. Average NWS error for the below (above) normal GFS confidence forecasts was 5.20oF (3.08oF). A student t-test on these values revealed that there is a statistically significant difference to 95% confidence of the mean forecast error during low and high confidence GFS forecasts. That is, the mean WFO forecast error is significantly increased during times of low forecast confidence in the GFS ensemble. Therefore, forecasters have a-priori knowledge of the likely human forecast error when they see the GFS ensemble output-- before the NWS forecast even verifies. During cases of extreme low confidence where the current model standard deviation is greater than the 25-year observational standard deviation, a climatology forecast was found to be more accurate than the overall ensemble mean. Although the confidence graphics are only based on the GFS ensembles as of now, more models will be added in the future to see how they behave when compared to each other. The GFS ensembles and the corresponding confidence technique have been used in the FSU-MM5 to see how a mesoscale model affects the overall confidence for a specific case. Recent feedback from NWS employees suggests an additional development of confidence graphics based on the "poor man's ensemble", which is an ensemble of all the operational forecast models. Eventually these graphics of below and above average confidence may be implemented into the Graphical Forecast Editor (GFE) for use in the National Digital Forecast Database (NDFD).
Show less
Date Issued: 2006
Identifier: FSU_migr_etd-0627
Format: Thesis

Title: Assessing the Potential Impact of Gifts Data to Severe Convective Precipitation Prediction.
Creator: Yorsaner, Mark Evan, Zou, Xiaolei, Hart, Robert, Ruscher, Paul, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A two-phase study of the potential impact of Geosynchronous Imaging Fourier Transfer Spectrometer (GIFTS) radiance data to the prediction of strong convective events was developed. In the first phase of the project, a statistical analysis of six runs of the Fifth Generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5), version 3, was performed. These runs incorporate different size domains, numbers of vertical levels, numbers of nesting domains,...
Show moreA two-phase study of the potential impact of Geosynchronous Imaging Fourier Transfer Spectrometer (GIFTS) radiance data to the prediction of strong convective events was developed. In the first phase of the project, a statistical analysis of six runs of the Fifth Generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5), version 3, was performed. These runs incorporate different size domains, numbers of vertical levels, numbers of nesting domains, and physical schemes. Using high-resolution National Center for Environmental Prediction (NCEP) Stage IV precipitation estimates, mesonet data, and radar reflectivity, it was determined that of all runs, one was chosen as being most appropriate for simulating GIFTS radiance. This run incorporates the simple ice microphysical scheme, the Grell cumulus scheme, the Blackadar planetary boundary layer scheme, and a simple atmospheric radiation scheme. Furthermore, this run was nested, with the mother domain (12-km resolution) of size 163 x 127 x 54 and the nested domain (4-km resolution) of size 103 x 127 x 54. In the second phase of the project, two sensitivity studies were carried out. In the first sensitivity study, the sensitivity of simulated GIFTS radiance to temperature and water vapor were examined. The 14 most sensitive channels within the GIFTS spectral range, out of 3,073, were chosen for further analysis. Through an analysis of an MM5 grid point that had relatively minimal cloud cover, it was determined that the most sensitive atmospheric layers at eight channels are in the lower troposphere (temperature) and lower to mid-troposphere (water vapor). At the other six, the most sensitive region is in the mid- to upper troposphere. The layers of maximum sensitivity are consistent with peaks of the weighting functions of these channels. The second sensitivity study examined the sensitivity of convective precipitation forecasts to the initial conditions of temperature and water vapor. The purpose of this study was to "bridge" the results of the first sensitivity study to the MM5 quantitative precipitation forecast (QPF) results. It was found that the most sensitive region is over the Central Plains of the United States and that the convective QPF is most sensitive to both water vapor content and temperature in the low-levels of the troposphere. Furthermore, temperature is deemed more sensitive to convective QPFs than water vapor. The results from these sensitivity tests, when linked together, demonstrate that GIFTS radiance at the eight wavenumbers most sensitive in the lower troposphere may be more effective to improve QPF than higher wavenumber radiance and that temperature in the Central Plains is the key meteorological variable to which the convective QPF is most sensitive. In a future four-dimensional variational data assimilation (4D-Var) study, simulated and real atmospheric observations from various sources will be assimilated into the MM5, with the GIFTS model representing the observation operator. Through this current study, a better sense of the utility of data from GIFTS to the forecasting of convective precipitation is ascertained, which would help streamline the 4D-Var study.
Show less
Date Issued: 2005
Identifier: FSU_migr_etd-0856
Format: Thesis

Title: Geochemical and Geochronological Investigations in the Southern Appalachians, Southern Rocky Mountains and Deccan Traps.
Creator: Das, Reshmi, Odom, A. Leroy, Chanton, Jeffrey, Kish, Stephen A., Salters, Vincent J. M., Tull, James F., Department of Earth, Ocean and Atmospheric Sciences, Florida State...
Show moreDas, Reshmi, Odom, A. Leroy, Chanton, Jeffrey, Kish, Stephen A., Salters, Vincent J. M., Tull, James F., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: In the southernmost Appalachians, bimodal volcanics of Pumpkinvine Creek Formation (PCF) and its proposed equivalent, the Hillabee Greenstone (HG) have indistinguishable ages (~460 Ma) and trace element-REE pattern similar to an arc/back-arc type setting. Eplison 143Nd values of felsic members of the HG and PCF indicate involvement of Grenville crust during petrogenesis. U-Pb dates (900-1500)Ma of detrital zircons in PCF meta-sandstone cluster around 1100Ma. Nd-model ages of the Ashland...
Show moreIn the southernmost Appalachians, bimodal volcanics of Pumpkinvine Creek Formation (PCF) and its proposed equivalent, the Hillabee Greenstone (HG) have indistinguishable ages (~460 Ma) and trace element-REE pattern similar to an arc/back-arc type setting. Eplison 143Nd values of felsic members of the HG and PCF indicate involvement of Grenville crust during petrogenesis. U-Pb dates (900-1500)Ma of detrital zircons in PCF meta-sandstone cluster around 1100Ma. Nd-model ages of the Ashland-Wedowee Supergroup metasediments range between 943-1439 Ma and cluster around 1000 Ma. Rb-Sr whole rock and U-Pb zircon dates of the Mulberry Rock Gneiss also demonstrate an Ordovician age (~460 Ma). It is concluded that the PCF-HG arc formed on the Laurentian continental margin on Ashland-Wedowee sediments during Ordovician and remained outboard of the continent until final closure during Alleghenian orogeny. Geochronological investigations of the Tres Piedras Granite of northcentral New Mexico have revealed a sharp discordancy between Rb-Sr whole-rock and U-Pb zircon ages. Analyses of fifty individual zircons (most concordant) by LA-MS-ICPMS yield a ~1730 Ma magmatic crystallization age. Rb-Sr whole-rock isochron ages from separate localities are 1490+/-20 Ma and 1497+/-42 Ma. Sphene/whole-rock/biotite isochron ages and initial 87Sr/86Sr ratios from separate localities are indistinguishable from those of whole-rock isochrons. In both cases feldspar plots above the isochrons and appeared to be an open system as evidenced by 4% difference in 87Sr/86Sr in the core and rim of feldspar. Taken altogether, these data are interpreted to reflect a large (kilometer) scale redistribution and rehomogenization of strontium isotopes during an independently, well-documented metamorphic event in the region. The geochemical character of the Kutch volcanics, northwest of Deccan Traps, India, have been investigated in order the magma's origin. Sr-Nd-Pb isotopic ratios and trace element patterns identifies three end members: Reunion plume-type alkali basalts, Mahabaleshwar-type alkali basalts and crustally contaminated tholeiites. The first type of alkali basalts that can be generated by very low degree of partial melting (1.6-1.8%) of Reunion plume like source at garnet stability field; the tholeiites can be explained by crustal contamination of Indian-MORB like magma. High 207Pb/204Pb (15.61-15.83) ratio of the tholeiites agrees well with the Pb-isotopes of local Archean crust.
Show less
Date Issued: 2006
Identifier: FSU_migr_etd-0840
Format: Thesis

Title: Statistical Forecasting of Florida Monthly Rainfall.
Creator: Wolf, Linden S., Ahlquist, Jon E., Sura, Philip, Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: This study computes statistical forecasts of monthly and three-monthly rainfall for seven regions of Florida defined by the National Climatic Data Center. First, time-lagged auto- and cross-correlations are computed involving monthly regional rainfall time series and various potential predictors. Various statistical monthly forecasting models are then built for each of the seven regions based on teleconnection indices and principal components of monthly heights of the global 500 hPa pressure...
Show moreThis study computes statistical forecasts of monthly and three-monthly rainfall for seven regions of Florida defined by the National Climatic Data Center. First, time-lagged auto- and cross-correlations are computed involving monthly regional rainfall time series and various potential predictors. Various statistical monthly forecasting models are then built for each of the seven regions based on teleconnection indices and principal components of monthly heights of the global 500 hPa pressure surface. To compare these forecasts to those of the Climate Prediction Center (CPC), the forecasts are categorized into terciles, corresponding to the upper, middle, and lower thirds of the climatological distribution of rainfall for each of the twelve months for each region. Following CPC, these are scored with the Heidke Skill Score. The variability of model coefficients and forecast skill is measured using cross-validation. The monthly Heidke Skill Score is low but generally better than a climatological forecast, which is CPC's standard of comparison. For most months and forecast regions, the Heidke Skill Score increases if a forecast for the middle tercile is replaced by a forecast that all three terciles are equally likely. Averaged over the year, the Florida Panhandle has the lowest monthly forecast skill, and Southwest Florida has the highest. April and May as well as September and October have low skill statewide. These times of year are associated with shifts in the prevailing winds as well as the El Nino-Southern Oscillation (ENSO) phase. Higher skills are obtained when forecasting the next three month's total precipitation than the next month's total precipitation. This increase in skill is largely due to the important of ENSO as a predictor and that ENSO is less noisy across three months than one month. A summer low in the forecast skill for three month's rain is due to the minimum in time-lagged correlation between late spring and summer. A middle tercile forecast for three-month rainfall is more likely to verify than a middle tercile forecast for one-month rainfall.
Show less
Date Issued: 2009
Identifier: FSU_migr_etd-0880
Format: Thesis

Title: Atlantic Reconnaissance Vortex Message Climatology and Composites and Their Use in Characterizing Eyewall Cycles.
Creator: Piech, David J., Hart, Robert, Clayson, Carol Anne, Fuelberg, Henry, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: There has been great energy focused on tropical cyclone intensity forecasting over the past thirty years. Toward the goal of providing more accurate intensity forecasts, the role of the environment of a tropical storm has been studied at great length over the past few years while the storm itself has not. There remains considerable work left toward understanding how the tropical cyclone structure itself can be used to aid intensity forecasting. One step toward this goal for the Atlantic is by...
Show moreThere has been great energy focused on tropical cyclone intensity forecasting over the past thirty years. Toward the goal of providing more accurate intensity forecasts, the role of the environment of a tropical storm has been studied at great length over the past few years while the storm itself has not. There remains considerable work left toward understanding how the tropical cyclone structure itself can be used to aid intensity forecasting. One step toward this goal for the Atlantic is by dissecting a climatology of reconnaissance vortex message reports from the Atlantic basin between 1989 and 2005. Such an analysis will permit the comparison of tropical cyclone core structure measurements to know future intensity change. This vortex message data, which is collected from dropsondes and radar during flights into tropical disturbances, includes eye size, pressure, eye temperature, eye dewpoint, maximum flight level winds and other pertinent information. The number of occurrences for each vortex message characteristic as well as frequency plots of eye type, Julian day, latitude, longitude, temperature, dewpoint, and intensity change as a function of mean sea level pressure (MSLP) and eye size were created. The composite mean eyewall cycle was analyzed, along with the cycles of concentric eyewalls and elliptical eyewalls. Based on this vortex message climatology and analysis, an eyewall phase diagram was developed that graphically shows the evolution of a storm. These eyewall phase diagrams show how eyewall cycles evolve in time using mean MSLP, mean eye size, concentric eyewall frequency, and elliptical eyewall frequency data. Case studies include analysis of a storm undergoing an eyewall replacement cycle (Rita 2005), a rapidly weakening storm (Charley 2004), and a rapidly intensifying storm (Wilma 2005). It was discovered in this study that core storm data collected from vortex data messages could be used to confirm theories on tropical cyclone intensity. Preliminary attempts at simple forecasts comparing eye characteristics and future intensity change were done. Indeed, short-term forecasts of intensity change should utilize storm-specific structure, beginning with an analysis of that structure in intensification versus weakening events. Further work involving pattern matching trajectories and trajectory segments to forecast future storm trajectory in the eyewall phase diagram may lead to helpful analog tropical cyclone intensity forecast guidance.
Show less
Date Issued: 2007
Identifier: FSU_migr_etd-0888
Format: Thesis

Title: Development of New Techniques for Assimilating Satellite Altimetry Data into Ocean Models.
Creator: Yu, Peng, O'Brien, James J., Zou, Xiaolei, Dewar, William K., Clarke, Allan J., Iverson, Richard, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: State of the art fully three-dimensional ocean models are very computationally expensive and their adjoints are even more resource intensive. However, many features of interest are approximated by the first baroclinic mode over much of the ocean, especially in the lower and mid latitude regions. Based on this dynamical feature, a new type of data assimilation scheme to assimilate sea surface height (SSH) data, a reduced-space adjoint technique, is developed and implemented with a three...
Show moreState of the art fully three-dimensional ocean models are very computationally expensive and their adjoints are even more resource intensive. However, many features of interest are approximated by the first baroclinic mode over much of the ocean, especially in the lower and mid latitude regions. Based on this dynamical feature, a new type of data assimilation scheme to assimilate sea surface height (SSH) data, a reduced-space adjoint technique, is developed and implemented with a three-dimensional model using vertical normal mode decomposition. The technique is tested with the Navy Coastal Ocean Model (NCOM) configured to simulate the Gulf of Mexico. The assimilation procedure works by minimizing the cost function, which generalizes the misfit between the observations and their counterpart model variables. The "forward" model is integrated for the period during which the data are assimilated. Vertical normal mode decomposition retrieves the first baroclinic mode, and the data misfit between the model outputs and observations is calculated. Adjoint equations based on a one-active-layer reduced gravity model, which approximates the first baroclinic mode, are integrated backward in time to get the gradient of the cost function with respect to the control variables (velocity and SSH of the first baroclinic mode). The gradient is input to an optimization algorithm (the limited memory Broyden-Fletcher-Goldfarb-Shanno (BFGS) method is used for the cases presented here) to determine the new first baroclinic mode velocity and SSH fields, which are used to update the forward model variables at the initial time. Two main issues in the area of ocean data assimilation are addressed: 1. How can information provided only at the sea surface be transferred dynamically into deep layers? 2. How can information provided only locally, in limited oceanic regions, be horizontally transferred to ocean areas far away from the data-dense regions, but dynamically connected to it? The first problem is solved by the use of vertical normal mode decomposition, through which the vertical dependence of model variables is obtained. Analyses show that the first baroclinic mode SSH represents the full SSH field very closely in the model test domain, with a correlation of 93% in one of the experiments. One common way to solve the second issue is to lengthen the assimilation window in order to allow the dynamic model to propagate information to the data-sparse regions. However, this dramatically increases the computational cost, since many oceanic features move very slowly. An alternative solution to this is developed using a mapping method based on complex empirical orthogonal functions (EOF), which utilizes data from a much longer period than the assimilation cycle and deals with the information in space and time simultaneously. This method is applied to map satellite altimeter data from the ground track observation locations and times onto a regular spatial and temporal grid. Three different experiments are designed for testing the assimilation technique: two experiments assimilate SSH data produced from a model run to evaluate the method, and in the last experiment the technique is applied to TOPEX/Poseidon and Jason-1 altimeter data. The assimilation procedure converges in all experiments and reduces the error in the model fields. Since the adjoint, or "backward", model is two-dimensional, the method is much more computationally efficient than if it were to use a fully three-dimensional backward model.
Show less
Date Issued: 2006
Identifier: FSU_migr_etd-0789
Format: Thesis

Title: Using Chemical Tracers to Evaluate Feeding Habits in Coastal Marine Ecosystems: Stable Isotopes and Organic Contaminants.
Creator: Wilson, Rachel Marie, Chanton, Jeffrey P., Cooper, William T., Nowacek, Douglas P., Kucklick, John R., Wang, Yang, Burnett, William C., Department of Earth, Ocean and...
Show moreWilson, Rachel Marie, Chanton, Jeffrey P., Cooper, William T., Nowacek, Douglas P., Kucklick, John R., Wang, Yang, Burnett, William C., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Show less
Abstract/Description: The use of chemical tracers to understand ecosystem interactions in the marine environment has gained increasing popularity over the past three decades. Carbon isotope abundances in organic matter sources in the marine system vary significantly making them a useful tracer for discriminating among such sources. Once taken up by primary producers, carbon isotope abundances are conservative throughout the food web. This allows us to measure carbon isotope abundances in secondary (and above)...
Show moreThe use of chemical tracers to understand ecosystem interactions in the marine environment has gained increasing popularity over the past three decades. Carbon isotope abundances in organic matter sources in the marine system vary significantly making them a useful tracer for discriminating among such sources. Once taken up by primary producers, carbon isotope abundances are conservative throughout the food web. This allows us to measure carbon isotope abundances in secondary (and above) consumers and infer organic matter source utilization in the system. Nitrogen isotope abundances, unlike carbon, are not conservative throughout the food web. However, they do fractionate predictably providing a tool by which to measure trophic level of consumer species. Sulfur isotopes, like carbon, differ among sources and are also conservative within the food web providing an additional tracer with which to estimate source contributions. However, concerns about the "dirtiness" of sulfur for analysis purposes put sulfur on the back burner as an ecosystem tracer. With recent improvements in technology and the need for multiple tracers in multi-source systems, sulfur isotope abundance measurements have experienced a resurgence. In this manuscript we use sulfur isotope abundances as a second tracer (with carbon isotope abundances) to estimate organic matter source utilization by consumers in a variety of habitats along the Florida Big Bend coastline. We begin our isotopic analysis of consumers in a Northwest Gulf of Mexico, freshwater dominated estuarine system, Apalachicola Bay, Florida (USA). In Chapter II we evaluate isotopic variation with body size to determine the smallest trophic unit in our system. In Chapter III we develop a concentration-corrected, dual-isotope, multi-source evaluation of organic matter utilization incorporating sulfur as a secondary tracer. We then go on to apply the results of this model to determine trophic level of consumers in Apalachicola Bay based on nitrogen isotope abundance data. In Chapter IV we demonstrate how isotopic variation of sources within a system can confound our interpretations of trophic structure using these methods. We further demonstrate that, in addition to isotopic variation, source inputs and availability may also vary within a given system. This makes comparison among sites more difficult and highlights the need to evaluate isotopic variation in individual systems prior to making comparisons or widespread generalizations about interactions. In Chapter V we apply these methods to a coastal seagrass community. We evaluate isotopic abundances in sources in consumers from the site. Then we apply the mixing model we develop in Chapter II to determine organic matter source utilization by consumers. Finally, we evaluate trophic level of individual consumers and trophic structure of the system based on nitrogen isotopic abundances. We demonstrate that source isotopic abundances differ from those same sources in the freshwater estuarine habitats. We also show that, while benthic organic matter was an important source in Apalachicola Bay, epiphytes provide the major organic matter source supporting consumers in the seagrass habitat. We use source utilization information and trophic level to assign consumers to trophic guilds in this system. The variety of organic matter source utilization is thought to contribute to the high levels of productivity found in this region. In addition to natural tracers, such as isotope abundances, we have also used organic pollutants as tracers of habitat utilization in the Florida Big Bend region. Organic contaminants found in coastal waters include compounds such as DDTs, PCBs, and chlordanes. Although no longer produced in the U.S., their historically wide-spread use and resistance to degradation contributes to their persistence in marine biota. We present data on chemical concentrations and congener profiles in bottlenose dolphins (Tursiops truncatus) and two abundant fish species from this region in Chapter VI. Although this area has been called "pristine" by previous researchers, we demonstrate the relativeness of this term, revealing that even the "forgotten coast" has been influenced by these ubiquitous contaminants. We use these compounds as tracers to evaluate bottlenose dolphin habitat utilization patterns in Florida Big Bend coastal waters. We found that the dolphins we sampled have differences in concentrations and patterns of contaminant loading indicating preference for feeding in specific areas and bays. Our results agree with suggestions based on sighting information that animals from the east and west regions of our study site rarely comingle and that even in the western site, individual animals express preferences for either St Joseph or St Andrews Bay foraging grounds.
Show less
Date Issued: 2010
Identifier: FSU_migr_etd-0901
Format: Thesis

Title: The Accuracy of the National Hurricane Center's United States Tropical Cyclone Landfall Forecasts in the Atlantic Basin (2004–2012).
Creator: Keclik, Alexandra, Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: This study examined the position, timing, and intensity of each National Hurricane Center's (NHC) Official Forecasts (OFCL) for Atlantic tropical storms and hurricanes that made landfall in the United States from 2004 to 2012. During that time period, one hundred and fifty tropical cyclones developed in the Atlantic basin. Thirty-two of the cyclones made landfall in the United States as tropical storms or hurricanes. Accurate predictions of the location, timing, and intensity of tropical...
Show moreThis study examined the position, timing, and intensity of each National Hurricane Center's (NHC) Official Forecasts (OFCL) for Atlantic tropical storms and hurricanes that made landfall in the United States from 2004 to 2012. During that time period, one hundred and fifty tropical cyclones developed in the Atlantic basin. Thirty-two of the cyclones made landfall in the United States as tropical storms or hurricanes. Accurate predictions of the location, timing, and intensity of tropical cyclone landfalls are important, so that people in a storm's track can prepare adequately for heavy to catastrophic wind, rain, and storm surge. The errors of each of the OFCL for Atlantic tropical storms and hurricanes that made landfall in the United States during 2004–2012 are acquired from the Best Track data set. The ELTOPO1 landmask is used to find the forecasted landfall point using sequential locations from the OFCL offshore and onshore points of each forecast. The great circle distance between the forecasted and actual landfall constitutes the location error. The official landfall time is subtracted from the forecasted landfall time to find the timing error, and the official landfall wind speed is subtracted from the closest to onshore wind speed to find intensity error. There is a trend of decreasing error in location, timing, and intensity forecasting with decreasing lead time. An improvement in tropical cyclone landfall forecasting is found from comparing the 2004–2012 Atlantic landfall forecast errors to those in a study of 1976-2000 forecasts.
Show less
Date Issued: 2014
Identifier: FSU_migr_uhm-0324
Format: Thesis

Title: Analysis of Convective Transport of Biomass Burning Emissions in Southeast Asia.
Creator: Ahern, Kyle, Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: Biomass burning and anthropogenic emissions affect the composition of the atmosphere, thereby impacting global climate and health. Deep convective processes can loft emissions from the boundary layer into the upper troposphere or lower stratosphere (UTLS). Strong upper-level winds can potentially transport the emissions over long distances. This study focused on the deep convective transport of biomass burning emissions near the Strait of Malacca during summer. The Weather Research and...
Show moreBiomass burning and anthropogenic emissions affect the composition of the atmosphere, thereby impacting global climate and health. Deep convective processes can loft emissions from the boundary layer into the upper troposphere or lower stratosphere (UTLS). Strong upper-level winds can potentially transport the emissions over long distances. This study focused on the deep convective transport of biomass burning emissions near the Strait of Malacca during summer. The Weather Research and Forecasting (WRF) and Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT_4) models were used to investigate deep convection and the transport of emissions from fires in the region. Fire data from the Moderate-resolution Imaging Spectroradiometer (MODIS) sensors onboard the Aqua and Terra satellites provided locations of fire emissions. These fire datasets were obtained from the University of Maryland's Fire Information for Resource Management System (FIRMS). To investigate the deep convective processes thoroughly, this study used high resolution modeling (4 km grid spacing) to resolve the convection explicitly. Explicit resolution allows the thunderstorms to be simulated more realistically than would parameterization, thus making it ideal for this research. Results showed that deep convection occurring in the Strait of Malacca is driven primarily by diurnal heating patterns and the region's topography. Convection in the region is frequent and scattered, but follows a cyclic diurnal pattern: convection over land during daytime and over the Strait during nighttime. When emissions from fires encounter areas of deep convection, they are quickly lofted to the UTLS where winds then transport them elsewhere.
Show less
Date Issued: 2013
Identifier: FSU_migr_uhm-0216
Format: Thesis

Theses and Dissertations (375)	+ -
Undergraduate Honors Theses (12)	+ -

Oceanography (248)	+ -
Atmospheric sciences (228)	+ -
Meteorology (222)	+ -
Earth sciences (135)	+ -
Geophysics (109)	+ -

Geology (15)	+ -
Atmospheric physics (9)	+ -
Climate (3)	+ -
Ecology (2)	+ -
Evolution (Biology) (2)	+ -
Biology (1)	+ -
Data processing (1)	+ -
Geomorphology (1)	+ -
Longitudinal method (1)	+ -
Philosophy (1)	+ -
Probabilities (1)	+ -
Sedimentology (1)	+ -
Seismology (1)	+ -
Time-series analysis (1)	+ -

Florida State University (375)	+ -
Hart, Robert (74)	+ -
Liu, Guosheng (62)	+ -
Krishnamurti, T. N. (43)	+ -
Ruscher, Paul (41)	+ -

Fuelberg, Henry E. (37)	+ -
Wang, Yang (35)	+ -
Bourassa, Mark (34)	+ -
Clayson, Carol Anne (34)	+ -
Zou, Xiaolei (33)	+ -
Huettel, Markus (26)	+ -
Sura, Philip (25)	+ -
Bourassa, Mark A. (23)	+ -
Cai, Ming (23)	+ -
Fuelberg, Henry (23)	+ -
Ruscher, Paul H. (23)	+ -
Cunningham, Philip (19)	+ -
Nof, Doron (18)	+ -
Dewar, William (17)	+ -
Kostka, Joel (17)	+ -
Burnett, William (16)	+ -
Chanton, Jeffrey (16)	+ -
Hart, Robert E. (16)	+ -
Wise, Sherwood W. (16)	+ -
Ellingson, Robert G. (15)	+ -
O'Brien, James J. (15)	+ -
Donoghue, Joseph F. (14)	+ -
Landing, William M. (14)	+ -
Misra, Vasubandhu (14)	+ -

Search In

Pages

Pages

Sort Results By:

Narrow results by:

Collection

Topical Subject

Genre

Type of Resource

Language

Creator

Owner