Search results

Title: Analysis methods for characterizing salinity variability from multivariate time series applied to the Apalachicola Bay estuary.
Creator: Morey, Steven, Dukhovskoy, Dmitry
Abstract/Description: Statistical analysis methods are developed to quantify the impacts of multiple forcing variables on the hydrographic variability within an estuary instrumented with an enduring observational system. The methods are applied to characterize the salinity variability within Apalachicola Bay, a shallow multiple-inlet estuary along the northeastern Gulf of Mexico coast. Thirteen-year multivariate time series collected by the National Estuary Research Reserve at three locations within the bay are...
Show moreStatistical analysis methods are developed to quantify the impacts of multiple forcing variables on the hydrographic variability within an estuary instrumented with an enduring observational system. The methods are applied to characterize the salinity variability within Apalachicola Bay, a shallow multiple-inlet estuary along the northeastern Gulf of Mexico coast. Thirteen-year multivariate time series collected by the National Estuary Research Reserve at three locations within the bay are analyzed to determine how the estuary responds to variations in external forcing mechanisms, such as freshwater discharge, precipitation, tides and local winds, at multiple time scales. The analysis methods are used to characterize the estuarine variability under differing flow regimes of the Apalachicola River, a managed waterway, with particular focus on extreme events and scales of variability that are critical to local ecosystems. Multivariate statistical models are applied that describe the salinity response to winds from multiple directions, river flow, and precipitation at daily, weekly, and monthly time scales to understand the response of the estuary under different climate regimes. Results show that the salinity is particularly sensitive to river discharge and wind magnitude and direction, with local precipitation being largely unimportant. Applying statistical analyses with conditional sampling quantifies how the likelihoods of high salinity and long duration high salinity events, conditions of critical importance to estuarine organisms, change given the state of the river flow. Intraday salinity range is shown to be negatively correlated with the salinity, and correlated with river discharge rate.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0047, 10.1175/JTECH-D-11-00136.1
Format: Citation

Title: Evaluation of dynamically downscaled reanalysis precipitation data for hydrological application in the southeast United States.
Creator: Bastola, Satish, Misra, Vasubandhu
Abstract/Description: Skillful and reliable precipitation data is essential for seasonal hydrologic forecasting, and generation of hydrological data. Though output from dynamic downscaling methods is used for hydrological application, the existence of systematic errors in dynamically downscaled data adversely affects the skill of hydrologic forecasting. This study evaluates the precipitation data derived by dynamically downscaling the global atmospheric reanalysis data by propagating them through three...
Show moreSkillful and reliable precipitation data is essential for seasonal hydrologic forecasting, and generation of hydrological data. Though output from dynamic downscaling methods is used for hydrological application, the existence of systematic errors in dynamically downscaled data adversely affects the skill of hydrologic forecasting. This study evaluates the precipitation data derived by dynamically downscaling the global atmospheric reanalysis data by propagating them through three hydrological models. Hydrological models are calibrated for 28 basins located in the southeast United States (U.S.) that is minimally affected by human intervention. Calibrated hydrological models are forced with five different types of datasets: global (NCEP R2 and ERA40) at their native resolution; dynamically downscaled; synthetically generated; bias-corrected, dynamically downscaled and bias-corrected global reanalysis. Our study indicates that over the 28 watersheds in the southeast U.S., the simulated hydrological response to the biascorrected dynamically downscaled data is superior. In comparison to synthetically generated meteorological forcing, the dynamically downscaled data result in more realistic hydrological simulations. Therefore, we conclude that dynamical downscaling, although resource intensive, is better suited for hydrological simulation in the southeast U.S.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0057
Format: Citation

Title: Generation of an empirical soil moisture initialization and its potential impact on subseasonal forecasting skill of continental precipitation and air temperature.
Creator: Boisserie, Marie
Abstract/Description: The effect of the PAR technique on the model soil moisture estimates is evaluated using the Global Soil Wetness Project Phase 2 (GSWP-2) multimodel analysis product (used as a proxy for global soil moisture observations) and actual in-situ observations from the state of Illinois. The results show that overall the PAR technique is effective; across most of the globe, the seasonal and anomaly variability of the model soil moisture estimates well reproduce the values of GSWP-2 in the top 1.5 m...
Show moreThe effect of the PAR technique on the model soil moisture estimates is evaluated using the Global Soil Wetness Project Phase 2 (GSWP-2) multimodel analysis product (used as a proxy for global soil moisture observations) and actual in-situ observations from the state of Illinois. The results show that overall the PAR technique is effective; across most of the globe, the seasonal and anomaly variability of the model soil moisture estimates well reproduce the values of GSWP-2 in the top 1.5 m soil layer; by comparing to in-situ observations in Illinois, we find that the seasonal and anomaly soil moisture variability is also well represented deep into the soil. Therefore, in this study, we produce a new global soil moisture analysis dataset that can be used for many land surface studies (crop modeling, water resource management, soil erosion, etc.). Then, the contribution of the resulting soil moisture analysis (used as initial conditions) on air temperature and precipitation forecasts are investigated. For this, we follow the experimental set up of a model intercomparison study over the time period 1986-1995, the Global Land-Atmosphere Coupling Experiment second phase (GLACE-2), in which the FSU/COAPS climate model has participated. The results of the summertime air temperature forecasts show a significant increase in skill across most of the U.S. at short-term to subseasonal time scales. No increase in summertime precipitation forecasting skill is found at short-term to subseasonal time scales between 1986 and 1995, except for the anomalous drought year of 1988. We also analyze the forecasts of two extreme hydrological events, the 1988 U.S. Drought and the 1993 U.S. flood. In general, the comparison of these two extreme hydrological event forecasts shows greater improvement for the summertime of 1988 than that of 1993, suggesting that soil moisture contributes more to the development of a drought than a flood. This result is consistent with Dirmeyer and Brubaker [1999] and Weaver et al. [2009]. By analyzing the evaporative sources of these two extreme events using the back-trajectory methodology of Dirmeyer and Brubaker [1999], we find similar results as this latter paper; the soil moisture-precipitation feedback mechanism seems to play a greater role during the drought year of 1988 than the flood year of 1993. Finally, the accuracy of this soil moisture initialization depends upon the quality of the precipitation dataset that is assimilated. Because of the lack of observed precipitation at a high temporal resolution (3-hourly) for the study period (1986-1995), a reanalysis product is used for precipitation assimilation in this study. It is important to keep in mind that precipitation data in reanalysis sometimes differ significantly from observations since precipitation is often not assimilated into the reanalysis model. In order to investigate that aspect, a similar analysis to that we performed in this study could be done using the 3-hourly Tropical Rainfall Measuring Mission (TRMM) dataset available for a the time period 1998-present. Then, since the TRMM dataset is a fully observational dataset, we expect the soil moisture initialization to be improved over that obtained in this study, which, in turn, may further increase the forecast skill.
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Date Issued: 2010
Identifier: FSU_migr_coaps_pubs-0002, fsu:209864
Format: Citation

Title: Generation of mesoscale eddies in the lee of the Hawaiian Islands.
Creator: Jia, Yinglai, Calil, P., Chassignet, E., Metzger, E., Potemra, J., Richards, K., Wallcraft, Alan J.
Abstract/Description: The ocean west of the main Hawaiian Islands is characterized by enhanced eddy kinetic energy arising from the abundance of locally generated mesoscale eddies, most frequently in the area west of the island of Hawaii. Two mechanisms of eddy generation in the wake of an island are examined with numerical model experiments. The first, eddy generation and shedding by an oceanic flow around an oceanic barrier, requires the existence of strong westward flows to the north and south of the island of...
Show moreThe ocean west of the main Hawaiian Islands is characterized by enhanced eddy kinetic energy arising from the abundance of locally generated mesoscale eddies, most frequently in the area west of the island of Hawaii. Two mechanisms of eddy generation in the wake of an island are examined with numerical model experiments. The first, eddy generation and shedding by an oceanic flow around an oceanic barrier, requires the existence of strong westward flows to the north and south of the island of Hawaii. Model solutions show such westward flows and generation of eddies by these flows although the intensity of the eddies and the generation frequency are much lower than that derived from altimetry. As a result, these eddies contribute an insignificant amount of eddy kinetic energy in the region. The second, eddy generation and shedding by an atmospheric flow around an atmospheric barrier, is based on oceanic upwelling and downwelling induced by surface wind shear, effectively introducing sinks and sources to the ocean interior. Previous idealized modeling studies have shown that oceanic eddies can be generated by sufficiently strong forcing (source or sink), providing an explanation why eddy occurrences in the lee of the island of Hawaii coincide with periods of strong trade winds. Eddy generation characteristics in the model experiments are consistent with this mechanism in terms of time of occurrence, strength and the resulting eddy kinetic energy. Major discrepancies are in eddy propagation and therefore eddy distribution in the regional domain due to the complex nature of eddy-eddy interactions.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0051, 10.1029/2011JC007305
Format: Citation

Title: Evolution of Land Surface Air Temperature Trend.
Creator: Ji, Fei, Wu, Zhaohua, Huang, Jianping, Chassignet, E.
Abstract/Description: The global climate has been experiencing significant warming at an unprecedented pace in the past century1, 2. This warming is spatially and temporally non-uniform, and one needs to understand its evolution in order to better evaluate its potential societal and economic impact. In this paper, the evolution of global land surface temperature trend in the last century is diagnosed using the spatial–temporally multidimensional ensemble empirical mode decomposition method3. We find that the...
Show moreThe global climate has been experiencing significant warming at an unprecedented pace in the past century1, 2. This warming is spatially and temporally non-uniform, and one needs to understand its evolution in order to better evaluate its potential societal and economic impact. In this paper, the evolution of global land surface temperature trend in the last century is diagnosed using the spatial–temporally multidimensional ensemble empirical mode decomposition method3. We find that the noticeable warming (>0.5 K) started sporadically over the global land and accelerated until around 1980. Both the warming rate and spatial structure have changed little since. The fastest warming in recent decades (>0.4 K/decade) occurred in northern midlatitudes. From a zonal average perspective, noticeable warming (>0.2 K since 1900) first took place in the subtropical and subpolar regions of the Northern Hemisphere, followed by subtropical warming in the Southern Hemisphere. The two bands of warming in the Northern Hemisphere expanded from 1950 to 1985 and merged to cover the entire Northern Hemisphere.
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Date Issued: 2014
Identifier: FSU_migr_coaps_pubs-0064, 10.1038/nclimate2223
Format: Set of related objects

Title: High-latitude ocean and sea ice surface fluxes: requirements and challenges for climate research.
Creator: Bourassa, Mark, Gille, Sarah Tragler, Bitz, Cecilia M., Carlson, David, Cerovecki, Ivana, Cronin, Meghan, Drennan, Will, Fairall, Chris, Hoffman, Ross, Magusdottir, Gudrun,...
Show moreBourassa, Mark, Gille, Sarah Tragler, Bitz, Cecilia M., Carlson, David, Cerovecki, Ivana, Cronin, Meghan, Drennan, Will, Fairall, Chris, Hoffman, Ross, Magusdottir, Gudrun, Pinker, Rachel, Renfrew, Ian, Serreze, Mark C., Speer, Kevin G. (Kevin George), Talley, Lynne D., Wick, Gary
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Abstract/Description: Improving knowledge of air-sea exchanges of heat, momentum, fresh water, and gases is critical to understanding climate, and this is particularly true in high-latitude regions, where anthropogenic climate change is predicted to be exceptionally rapid. However, observations of these fluxes are extremely scarce in the Arctic, the Southern Ocean, and the Antarctic marginal seas. High winds, high sea state, extreme cold temperatures, seasonal sea ice, and the remoteness of the regions all...
Show moreImproving knowledge of air-sea exchanges of heat, momentum, fresh water, and gases is critical to understanding climate, and this is particularly true in high-latitude regions, where anthropogenic climate change is predicted to be exceptionally rapid. However, observations of these fluxes are extremely scarce in the Arctic, the Southern Ocean, and the Antarctic marginal seas. High winds, high sea state, extreme cold temperatures, seasonal sea ice, and the remoteness of the regions all conspire to make observations difficult to obtain. Annually averaged heat-flux climatologies can differ by more than their means, and in many cases there is no clear consensus about which flux products are most reliable. Although specific flux accuracy requirements for climate research vary depending on the application, in general fluxes would better represent high-latitude processes if wind stresses achieved 0.01Nm-2 accuracy at high wind speed and if heat fluxes achieved 10 W m-2 accuracy (averaged over several days) with 25 km grid spacing. Improvements in flux estimates will require a combination of efforts, including a concerted plan to make better use of ships of opportunity to collect meteorological data, targeted efforts to deploy a few flux moorings in high-wind regions, and improved satellite retrievals of flux-related variables.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0017
Format: Citation

Title: High-resolution satellite surface latent heat fluxes in North Atlantic hurricanes.
Creator: Liu, Jiping, Curry, Judith A., Clayson, Carol Anne, Bourassa, Mark
Abstract/Description: This study presents a new high-resolution satellite-derived ocean surface flux product, XSeaFlux, which is evaluated for its potential use in hurricane studies. The XSeaFlux employs new satellite data sets using improved retrieval methods, and uses a new bulk flux algorithm formulated for high wind conditions. The XSeaFlux latent heat flux (LHF) performs much better than the existing numerical weather prediction reanalysis and satellite-derived flux products in a comparison with measurements...
Show moreThis study presents a new high-resolution satellite-derived ocean surface flux product, XSeaFlux, which is evaluated for its potential use in hurricane studies. The XSeaFlux employs new satellite data sets using improved retrieval methods, and uses a new bulk flux algorithm formulated for high wind conditions. The XSeaFlux latent heat flux (LHF) performs much better than the existing numerical weather prediction reanalysis and satellite-derived flux products in a comparison with measurements from the Coupled Boundary Layer Air-Sea Transfer (CBLAST) field experiment. Also, the XSeaFlux shows well-organized LHF structure and large LHF values in response to hurricane conditions relative to the other flux products. The XSeaFlux data set is used to interpret details of the ocean surface LHF for selected North Atlantic hurricanes. Analysis of the XSeaFlux data set suggests that ocean waves, sea spray, and cold wake have substantial impacts on LHF associated with the hurricanes.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0023, 10.1175/2011MWR3548.1
Format: Citation

Title: California reanalysis downscaling at 10 km using an ocean-atmosphere coupled regional model system.
Creator: Li, Haiqin, Kanamitsu, Masao, Hong, Song-You
Abstract/Description: A fully coupled regional downscaling system for both the Regional Spectral Model (RSM) for atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean was developed for the purpose of downscaling observed analysis or global model outputs. The two models share the same grid and resolution with efficient parallelization through the use of dual message passing interfaces. Coupled downscaling was performed using historical Simple Ocean Data Assimilation (SODA) oceanic reanalysis and...
Show moreA fully coupled regional downscaling system for both the Regional Spectral Model (RSM) for atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean was developed for the purpose of downscaling observed analysis or global model outputs. The two models share the same grid and resolution with efficient parallelization through the use of dual message passing interfaces. Coupled downscaling was performed using historical Simple Ocean Data Assimilation (SODA) oceanic reanalysis and NCEP/DOE (R-2) atmospheric reanalysis in order to study the impact of coupling on the regional scale atmospheric analysis. The results were subsequently compared with the uncoupled downscaling forced by the prescribed observed sea surface temperature (SST). An evaluation of the SST and ocean current from the coupled experiment yielded realistic small-scale oceanic features that are nearly absent in the oceanic reanalysis. Upwelling over the California coast is well resolved and comparable to findings obtained from high-resolution observations. The coupling impact on the atmospheric circulation mainly modulates the near surface atmospheric variables when compared to the simulation conducted without coupling. The duration of the Catalina Eddy detected in the coupled experiment increased by about 6.5% when compared to that in the uncoupled experiment. The offshore land breeze is enhanced by about 10%, whereas the change in the onshore sea breeze is very small during the summer.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0059, 10.1029/2011JD017372
Format: Citation

Title: Climate Data Issues from an Oceanographic Remote Sensing Perspective.
Creator: Katsaros, Kristina, Bentamy, Abderrahim, Bourassa, Mark, Ebuchi, Naoto, Gower, James, Liu, W., Vignudelli, Stefano
Abstract/Description: In this chapter we review several climatologically important variables with a history of observation from spaceborne platforms. These include sea surface temperature and wind vectors, altimetric estimates of sea surface height, energy and water vapor fluxes at the sea surface, precipitation over the ocean, and ocean color. We then discuss possible improvements in sampling for climate and climate change definition. Issues of consistency of different data sources, archiving and distribution of...
Show moreIn this chapter we review several climatologically important variables with a history of observation from spaceborne platforms. These include sea surface temperature and wind vectors, altimetric estimates of sea surface height, energy and water vapor fluxes at the sea surface, precipitation over the ocean, and ocean color. We then discuss possible improvements in sampling for climate and climate change definition. Issues of consistency of different data sources, archiving and distribution of these types of data are discussed. The practical prospect of immediate international coordination through the concept of virtual constellations is discussed and applauded.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0062, 10.1007/978-3-642-16541-2_2
Format: Citation

Title: On the variability of the Mediterranean Outflow Water in the Atlantic Ocean from 1948 to 2006.
Creator: Bozec, Alexandra, Lozier, M., Chassignet, E., Halliwell, George
Abstract/Description: Recent work has shown that variability in the properties and/or transport of Mediterranean Seawaters spilling across the Strait of Gibraltar into the North Atlantic have had little impact on the variability of Mediterranean Outflow Water (MOW) in the that basin over the past fifty years. Here we investigate whether circulation changes are the dominant source of MOW variability in the North Atlantic between 1948 and 2006. Using a 1/3° North Atlantic configuration of the HYbrid Coordinate Ocean...
Show moreRecent work has shown that variability in the properties and/or transport of Mediterranean Seawaters spilling across the Strait of Gibraltar into the North Atlantic have had little impact on the variability of Mediterranean Outflow Water (MOW) in the that basin over the past fifty years. Here we investigate whether circulation changes are the dominant source of MOW variability in the North Atlantic between 1948 and 2006. Using a 1/3° North Atlantic configuration of the HYbrid Coordinate Ocean Model combined with the Marginal Sea Boundary Condition model, two simulations forced by either climatological or interannual atmospheric fields are performed. The interannual simulation reproduces the observed MOW variability without Mediterranean Seawater changes. Thus, we conclude that MOW variability in the last 60 years is a consequence of circulation changes in the North Atlantic. A series of simulations that separate the mechanical effect of the wind from the impact of buoyancy forcing show that MOW variability can be attributed to shifts between its dominant northward and westward pathways. The pathway shifts from predominantly northward between 1950 and 1975 to predominantly westward between 1975 and 1995 and finally back to northward after 1995. Though these pathway shifts appear to be wind-induced, the property changes are caused by the combined impact of wind and buoyancy forcing on the circulation of the North Atlantic.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0015, 10.1029/2011JC007191
Format: Citation

Title: Operational marine forecasters and the importance of marine forecasting.
Creator: Sullivan, D., Murphree, Tom, Rosenfield, L., Smith, S.
Abstract/Description: A major goal of the Marine Advanced Technology Education (MATE) Center is to align curriculum and program development with the needs of employers. The Center believes that graduates from MATE-affiliated educational institutions should be well informed about workforce needs and well equipped with the skills required to enter marine technical occupations. To accomplish this, one of the methods used by the MATE Center is the development and use of Knowledge and Skill Guidelines. (Knowledge and...
Show moreA major goal of the Marine Advanced Technology Education (MATE) Center is to align curriculum and program development with the needs of employers. The Center believes that graduates from MATE-affiliated educational institutions should be well informed about workforce needs and well equipped with the skills required to enter marine technical occupations. To accomplish this, one of the methods used by the MATE Center is the development and use of Knowledge and Skill Guidelines. (Knowledge and Skill Guidelines may also be referred to as Occupational Guidelines or Standards or Skill Standards.) This document represents one such resource for Operational Marine Forecasters.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0013
Format: Citation

Title: A proxy for high-resolution regional reanalysis for the Southeast United States: assessment of precipitation variability in dynamically downscaled reanalyses.
Creator: Stefanova, Lydia, Misra, Vasubandhu, Chan, Steven, Griffin, Melissa, O'Brien, James J., Smith, III, Thomas
Abstract/Description: A variety of practical applications, such as hydrological and ecological modeling, require high-resolution meteorological data sets. A crucial, yet notoriously difficult to model, component of such data sets is precipitation. Here, we present an analysis of the seasonal, subseasonal, and diurnal variability of rainfall from the COAPS Land-Atmosphere Regional Reanalysis for the Southeast at 10-km resolution (CLARReS10). Most of our analysis focuses on the representation of summertime...
Show moreA variety of practical applications, such as hydrological and ecological modeling, require high-resolution meteorological data sets. A crucial, yet notoriously difficult to model, component of such data sets is precipitation. Here, we present an analysis of the seasonal, subseasonal, and diurnal variability of rainfall from the COAPS Land-Atmosphere Regional Reanalysis for the Southeast at 10-km resolution (CLARReS10). Most of our analysis focuses on the representation of summertime subseasonal and diurnal variability. Summer precipitation in the Southeast is a particularly challenging modeling problem because of the variety of regional-scale phenomena, such as sea breeze, thunderstorms and squall lines, tropical storms, and hurricanes, which are barely resolved in coarse atmospheric reanalyses, but which contribute significantly to the hydrological budget over the region. The National Centers for Environmental Prediction (NCEP) - Department of Energy (DOE) Reanalysis II (R2) and the European Centre for Medium-Range Weather Forecast (ECMWF) 40-year Reanalysis (ERA40) have been dynamically downscaled with the NCEP/Experimental Climate Prediction Center (ECPC) Regional Spectral Model (RSM). The downscaling has been performed over the Southeast United States at a horizontal resolution of 10 km for the period 1979-2001. The resulting regional reanalyses are compared to gridded observations and station data. We find that the downscaled reanalyses show good agreement with observations in terms of both the relative seasonal distribution and the diurnal structure of precipitation. The spatial distribution of precipitation has a wet bias over most of the region. There are noticeable differences between the two simulations: CLARReS10-ERA40 (the downscaled ERA40) tends to be wetter than CLARReS10-R2 (the downscaled R2), and the diurnal precipitation maximum occurs earlier in the day in CLARReS10- ERA40
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0027, 10.1007/s00382-011-1230-y
Format: Citation

Title: A vortex isolation and removal algorithm for numerical weather prediction model tropical cyclone applications.
Creator: Winterbottom, Henry R., Chassignet, E.
Abstract/Description: Inserting an externally defined (i.e., synthetic) tropical cyclone (TC) vortex into numerical weather prediction (NWP) model analyses requires that an existing TC vortex first be removed. Similarly, statistical-dynamical forecasting methods require that the larger-scale environmental attributes of the flow be separated (and preserved) from those on the smaller meso- and TC vortex scales. The existing operational methods to accomplish such tasks are optimized particularly for the respective...
Show moreInserting an externally defined (i.e., synthetic) tropical cyclone (TC) vortex into numerical weather prediction (NWP) model analyses requires that an existing TC vortex first be removed. Similarly, statistical-dynamical forecasting methods require that the larger-scale environmental attributes of the flow be separated (and preserved) from those on the smaller meso- and TC vortex scales. The existing operational methods to accomplish such tasks are optimized particularly for the respective models grid spacing resolution and thus are not general when applied to finer resolution analyses. Further, the existing methods often adhere to rigid assumptions regarding the size and structure of the TC. A methodology is provided in this study to overcome these limitations. This is accomplished through analyzing the features of the NWP model analysis (e.g., the variables in the vicinity of the TC) and then systematically removing the TC through the application of both a smoothing operator and a subsequent statistical evaluation of the smoothed analysis variable. The value of our methodology is determined when analyzing the results from experiments initialized from an analysis containing TCs and those initialized from analyses without the respective TCs. This methodology is also robust for it does not require a tuning of parameters relative to varying grid-spacing resolutions and may thus benefit the statistical-dynamical TC intensity prediction schemes.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0050, 10.1029/2011MS000088
Format: Citation

Title: Understanding wet season variations over Florida.
Creator: Misra, Vasubandhu, DiNapoli, Steven
Abstract/Description: The wet season of Florida is well defined and is invariably centered in the boreal summer season of June–July–August. In this observational study we objectively define the Length of the Wet Season (LOWS) for Florida and examine its variations with respect to El Niño and the Southern Oscillation (ENSO) and the Atlantic Warm Pool (AWP). Our study reveals that ENSO variability has a profound influence on the LOWS especially over south Florida and parts of panhandle Florida prior to 1976. In the...
Show moreThe wet season of Florida is well defined and is invariably centered in the boreal summer season of June–July–August. In this observational study we objectively define the Length of the Wet Season (LOWS) for Florida and examine its variations with respect to El Niño and the Southern Oscillation (ENSO) and the Atlantic Warm Pool (AWP). Our study reveals that ENSO variability has a profound influence on the LOWS especially over south Florida and parts of panhandle Florida prior to 1976. In the post-1976 era the influence of ENSO has significantly diminished. Our results show that in this pre-1976 era, warm (cold) ENSO events in the boreal winter are followed by long (short) LOWS over the region. This variation is consistent with warm (cold) ENSO events influencing early (late) onset of the wet season in the region. There is significant relationship of the LOWS in south and northeast Florida with the variation of the AWP. Unlike the teleconnection with ENSO the relationship of the demise of the wet season with AWP is stronger in the post-1976 period compared to the pre-1976 period. Furthermore the variability of the LOWS has increased in the post-1976 period.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0056, 10.1007/s00382-012-1382-4
Format: Citation

Title: A comparison of sequential assimilation schemes for ocean prediction with the HYbrid Coordinate Ocean Model (HYCOM). Part I: Twin experiments.
Creator: Srinivasan, A.
Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0022
Format: Citation

Title: Top-down, bottom-up and physical controls on diatom-diazotroph assemblage growth in the Amazon River plume.
Creator: Stukel, Michael, Coles, Victoria, Brooks, Maureen, Hood, Raleigh
Abstract/Description: The nutrient-rich waters of the Amazon River plume (ARP) support dense blooms of diatom-diazotroph assemblages (DDAs) that introduce large quantities of new nitrogen to the planktonic ecosystem and, unlike other nitrogen-fixers, are likely to directly fuel vertical carbon flux. To investigate the factors controlling DDA blooms, we develop a five phytoplankton (cyanobacteria, diatoms, unicellular microbial diazotrophs, DDAs, and Trichodesmium), two zooplankton model and embed it within a 1/6°...
Show moreThe nutrient-rich waters of the Amazon River plume (ARP) support dense blooms of diatom-diazotroph assemblages (DDAs) that introduce large quantities of new nitrogen to the planktonic ecosystem and, unlike other nitrogen-fixers, are likely to directly fuel vertical carbon flux. To investigate the factors controlling DDA blooms, we develop a five phytoplankton (cyanobacteria, diatoms, unicellular microbial diazotrophs, DDAs, and Trichodesmium), two zooplankton model and embed it within a 1/6° resolution physical model of the tropical and subtropical Atlantic. The model generates realistic DDA blooms in the ARP and also exhibits basin-wide primary production, nitrogen fixation, and grazing rates consistent with observed values. By following ARP water parcels with synthetic Lagrangian drifters released at the river mouth we are able to assess the relative impacts of grazing, nutrient supply, and physical forcing on DDA bloom formation. DDA bloom formation is stimulated in the nitrogen-poor and silica-rich water of the ARP by decreases in grazing pressure when mesozooplankton (which co-occur in high densities with coastal diatom blooms) concentrations decrease. Bloom termination is driven primarily by silica limitation of the DDAs. In agreement with in situ data, this net growth niche for DDAs exists in a salinity range from ∼20–34 PSU, although this co-occurrence is coincidental rather than causative. Because net growth rates are relatively modest, bloom formation in ARP water parcels depends critically on the time spent in this ideal habitat, with high DDA biomass only occurring when water parcels spent >23 days in the optimal habitat niche.
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Date Issued: 2014
Identifier: FSU_migr_eoas_faculty_publications-0001, 10.5194/bg-11-3259-2014
Format: Citation

Title: The arrested Agulhas retroflection.
Creator: Nof, Doron, Zharkov, Volodymyr, Ortiz, Joseph, Paldor, Nathan, Arruda, Wilton, Chassignet, E.
Abstract/Description: Paleoceanographic proxy data indicate that the Agulhas leakage into the South Atlantic was dramatically reduced during glacial times. In our former papers, we suggested that this was due to a northward shift of the zero wind stress curl that, in turn, forced the retroflection to occur farther north, where the slant of the coastline relative to the north is steep. In the present paper, we propose that strong westerlies (0.4 Pa, implying a wind speed of ~ 12 m s-1 at zero degrees centigrade),...
Show morePaleoceanographic proxy data indicate that the Agulhas leakage into the South Atlantic was dramatically reduced during glacial times. In our former papers, we suggested that this was due to a northward shift of the zero wind stress curl that, in turn, forced the retroflection to occur farther north, where the slant of the coastline relative to the north is steep. In the present paper, we propose that strong westerlies (0.4 Pa, implying a wind speed of ~ 12 m s-1 at zero degrees centigrade), which were supposedly common during glaciations, can also arrest the leakage. This arrest occurred because the wind stress opposed the momentum flux associated with the retroflection; such an arrest did not require the retroflection to shift in latitude. We use a simple, nonlinear, "reduced gravity" model to show analytically and numerically that, under the above conditions, the eastward wind stress compensates for the zonal westward flow-force associated with the retroflection, thus avoiding the development and shedding of rings. For a nearly zonal wall, westerly winds, and small upper layer thickness along the wall, the arresting wind stress is found, theoretically, to be, τx~0.042α3/2ρf[(2fQ)3/g']1/4 where α is twice the retroflection eddy vorticity, ρ the water density, and Q the Agulhas Current volume flux; the remaining notation is conventional.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0053, 10.1357/002224011799849453
Format: Citation

Title: A latent heat retrieval and its effects on the intensity and structure change of Hurricane Guillermo (1997). Part I: the algorithm and observations.
Creator: Guimond, S., Bourassa, Mark, Reasor, Paul
Abstract/Description: Despite the fact that latent heating in cloud systems drives many atmospheric circulations, including tropical cyclones, little is known of its magnitude and structure, largely because of inadequate observations. In this work, a reasonably high-resolution (2 km), four-dimensional airborne Doppler radar retrieval of the latent heat of condensation/evaporation is presented for rapidly intensifying Hurricane Guillermo (1997). Several advancements in the basic retrieval algorithm are shown,...
Show moreDespite the fact that latent heating in cloud systems drives many atmospheric circulations, including tropical cyclones, little is known of its magnitude and structure, largely because of inadequate observations. In this work, a reasonably high-resolution (2 km), four-dimensional airborne Doppler radar retrieval of the latent heat of condensation/evaporation is presented for rapidly intensifying Hurricane Guillermo (1997). Several advancements in the basic retrieval algorithm are shown, including 1) analyzing the scheme within the dynamically consistent framework of a numerical model, 2) identifying algorithm sensitivities through the use of ancillary data sources, and 3) developing a precipitation budget storage term parameterization. The determination of the saturation state is shown to be an important part of the algorithm for updrafts of -5 m s -1 or less. The uncertainties in the magnitude of the retrieved heating are dominated by errors in the vertical velocity. Using a combination of error propagation and Monte Carlo uncertainty techniques, biases are found to be small, and randomly distributed errors in the heating magnitude are ~16% for updrafts greater than 5 m s -1 and ~156% for updrafts of 1 m s -1. Even though errors in the vertical velocity can lead to large uncertainties in the latent heating field for small updrafts/downdrafts, in an integrated sense the errors are not as drastic. In Part II, the impact of the retrievals is assessed by inserting the heating into realistic numerical simulations at 2-km resolution and comparing the generated wind structure to the Doppler radar observations of Guillermo.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0018, 10.1175/2011JAS3700.1
Format: Citation

Title: A modeling study of the interaction between the Atlantic Warm Pool, the tropical Atlantic easterlies, and the Lesser Antilles.
Creator: Chan, Steven, Misra, Vasubandhu, Smith, H.
Abstract/Description: The European Centre for Medium-Range Forecasts Reanalysis-40 and National Centers for Environmental Prediction (NCEP)/Department of Energy reanalyses are downscaled over the eastern Caribbean and Lesser Antilles using the NCEP-Scripps Regional Spectral Model for Augusts when the Atlantic Warm Pool (AWP) area is the most anomalous. The simulations show a two-way influence between the Lesser Antilles and the AWP: the islands modulate the regional atmospheric circulation, and AWP variations...
Show moreThe European Centre for Medium-Range Forecasts Reanalysis-40 and National Centers for Environmental Prediction (NCEP)/Department of Energy reanalyses are downscaled over the eastern Caribbean and Lesser Antilles using the NCEP-Scripps Regional Spectral Model for Augusts when the Atlantic Warm Pool (AWP) area is the most anomalous. The simulations show a two-way influence between the Lesser Antilles and the AWP: the islands modulate the regional atmospheric circulation, and AWP variations modulate the interannual variabilities of the islands. The Lesser Antilles introduce diurnal variations and drag to the easterlies. The presence of the islands modulates the prevalent easterlies as a result of the daytime heating of the islands and the consequent boundary layer expansion. The modulations are sensitive to the islands' size and topography. Small and flat islands act as thermal plumes, but the modulations of large and hilly islands are during the daytime as their boundary layer expands. The manifestation of the atmospheric response to the sea surface temperature (SST) anomalies over the islands is sensitive to the island orography. For most islands, the atmospheric response to the SST anomalies is reflected only during the daytime. For all 1-grid-point islands and Antigua, nighttime and dawn minimum temperatures are modulated to the same degree as the daytime maximum. For island rainfall, downscaling reduces the gross overestimations of rainfall in the reanalyses. However, our downscaling results suggest that there is room for improvement in simulating the marine surface diurnal cycle.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0029, 10.1029/2010JD015260
Format: Citation

Title: The influence of the Atlantic Warm Pool on Panhandle Florida Sea Breeze.
Creator: Misra, Vasubandhu, Moeller, Lauren, Stefanova, Lydia, Chan, Steven, O'Brien, James J., Smith, III, Thomas, Plant, Nathaniel
Abstract/Description: In this paper we examine the variations of the boreal summer season sea breeze circulation along the Florida panhandle coast from relatively high resolution (10 km) regional climate model integrations. The 23 year climatology (1979-2001) of the multidecadal dynamically downscaled simulations forced by the National Centers for Environmental Prediction-Department of Energy (NCEP-DOE) Reanalysis II at the lateral boundaries verify quite well with the observed climatology. The variations at...
Show moreIn this paper we examine the variations of the boreal summer season sea breeze circulation along the Florida panhandle coast from relatively high resolution (10 km) regional climate model integrations. The 23 year climatology (1979-2001) of the multidecadal dynamically downscaled simulations forced by the National Centers for Environmental Prediction-Department of Energy (NCEP-DOE) Reanalysis II at the lateral boundaries verify quite well with the observed climatology. The variations at diurnal and interannual time scales are also well simulated with respect to the observations. We show from composite analyses made from these downscaled simulations that sea breezes in northwestern Florida are associated with changes in the size of the Atlantic Warm Pool (AWP) on interannual time scales. In large AWP years when the North Atlantic Subtropical High becomes weaker and moves further eastward relative to the small AWP years, a large part of the southeast U.S. including Florida comes under the influence of relatively strong anomalous low-level northerly flow and large-scale subsidence consistent with the theory of the Sverdrup balance. This tends to suppress the diurnal convection over the Florida panhandle coast in large AWP years. This study is also an illustration of the benefit of dynamic downscaling in understanding the low-frequency variations of the sea breeze.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0032, 10.1029/2010JD015367
Format: Citation

Title: Dynamic downscaling of the North American Monsoon with the NCEP-Scripps Regional Spectral Model from the NCEP CFS global model.
Creator: Chan, Steven, Misra, Vasubandhu
Abstract/Description: The June-September (JJAS) 2000-2007 NCEP coupled Climate Forecasting System (CFS) global hindcasts are downscaled over the North and South American continents with the NCEP-Scripps Regional Spectral Model (RSM) with anomaly nesting (AN) and without bias correction (control). A diagnosis of the North American Monsoon (NAM) in CFS and RSM hindcasts is presented here. RSM reduces errors caused by coarse resolution, but is unable to address larger scale CFS errors even with bias correction. CFS...
Show moreThe June-September (JJAS) 2000-2007 NCEP coupled Climate Forecasting System (CFS) global hindcasts are downscaled over the North and South American continents with the NCEP-Scripps Regional Spectral Model (RSM) with anomaly nesting (AN) and without bias correction (control). A diagnosis of the North American Monsoon (NAM) in CFS and RSM hindcasts is presented here. RSM reduces errors caused by coarse resolution, but is unable to address larger scale CFS errors even with bias correction. CFS has relatively weak Great Plains and Gulf of California low-level jets. Low-level jets are strengthened from downscaling, especially after AN bias correction. The RSM NAM hydroclimate shares similar flaws with CFS with problematic diurnal and seasonal variability. Flaws in both diurnal and monthly variability are forced by erroneous convection-forced divergence outside the monsoon core region in eastern and southern Mexico. NCEP Reanalysis shows significant seasonal variability errors, and AN shows little improvement in regional scale flow errors. Our results suggest extreme caution must be taken when the correction is applied relative to reanalyses. Analysis also shows North American Regional Reanalysis NAM seasonal variability has benefited from precipitation data assimilation, but many questions remain concerning NARR's representation of NAM.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0030, 10.1175/2010JCLI3593.1
Format: Citation

Title: Recent historically low global tropical cyclone activity.
Creator: Maue, Ryan Nicholas
Abstract/Description: Tropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40-years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the global frequency of tropical cyclones has reached a historical low. Here evidence is presented demonstrating that considerable variability in tropical cyclone ACE is associated with the...
Show moreTropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40-years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the global frequency of tropical cyclones has reached a historical low. Here evidence is presented demonstrating that considerable variability in tropical cyclone ACE is associated with the evolution of the character of observed large-scale climate mechanisms including the El Niño Southern Oscillation and Pacific Decadal Oscillation. In contrast to record quiet North Pacific tropical cyclone activity in 2010, the North Atlantic basin remained very active by contributing almost one-third of the overall calendar year global ACE.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0039, 10.1029/2011GL047711
Format: Citation

Title: Quantifying variance due to temporal and spatial difference between ship and satellite winds.
Creator: May, J., Bourassa, Mark
Abstract/Description: Ocean vector winds measured by SeaWinds can be validated with comparison in situ data that are within a certain time and space range to the satellite overpass. The total amount of random observational error is composed of two primary components, which are quantified in this study: the uncertainty associated with the data sets and the uncertainty associated with the temporal and/or spatial difference between two observations. The variance associated with a temporal difference, which can be...
Show moreOcean vector winds measured by SeaWinds can be validated with comparison in situ data that are within a certain time and space range to the satellite overpass. The total amount of random observational error is composed of two primary components, which are quantified in this study: the uncertainty associated with the data sets and the uncertainty associated with the temporal and/or spatial difference between two observations. The variance associated with a temporal difference, which can be translated into a spatial difference using Taylor's hypothesis, between two observations is initially examined in an idealized case that includes only Shipboard Automated Meteorological and Oceanographic System (SAMOS) 1 min data. The results show that the amount of variance in wind speed and direction increases as the time difference increases, while the amount of variance in wind speed increases and direction decreases with larger wind speeds. Collocated SeaWinds and SAMOS observations are used to determine the total amount of variance associated with a temporal (equivalent) difference from 0 to 60 min. For combined differences less than 25 min (equivalent) and the selected wind speed bins, the variance associated with the temporal and spatial difference is dominated by small changes in the wind speed distribution, and the sum of the observational errors is approximately 1.0 m2 s-12 (12 deg2) and 1.5 m2 s-2 (10 deg2) for wind speeds between 4 and 7 m s-1 and 7-12 m s-1. For larger combined differences, the observational error variance is no longer the dominant term; therefore, the total variance is seen to gradually increase with increasing time differences.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0024, 10.1029/2010JC006931
Format: Citation

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.
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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
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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.
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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.
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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.
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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.
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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.
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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
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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..
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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.
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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
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Date Issued: 2007
Identifier: FSU_migr_etd-0400
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
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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.
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Date Issued: 2007
Identifier: FSU_migr_etd-0511
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.
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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.
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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.
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Date Issued: 2003
Identifier: FSU_migr_etd-0285
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.
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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.
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Date Issued: 2006
Identifier: FSU_migr_etd-0237
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.
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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.
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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.
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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.
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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.
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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
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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.
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Date Issued: 2011
Identifier: FSU_migr_etd-0261
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.
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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.
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Date Issued: 2010
Identifier: FSU_migr_etd-0369
Format: Thesis

Title: Spatio-Temporal Evolutions of Non-Orthogonal Equatorial Wave Modes Derived from Observations.
Creator: Barton, Cory, Cai, Ming, Niu, Xufeng, Clarke, Allan J., Speer, Kevin G. (Kevin George), Sura, Philip, Florida State University, College of Arts and Sciences, Program in...
Show moreBarton, Cory, Cai, Ming, Niu, Xufeng, Clarke, Allan J., Speer, Kevin G. (Kevin George), Sura, Philip, Florida State University, College of Arts and Sciences, Program in Geophysical Fluid Dynamics
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Abstract/Description: Equatorial waves have been studied extensively due to their importance to the tropical climate and weather systems. Historically, their activity is diagnosed mainly in the wavenumber-frequency domain. Recently, many studies have projected observational data onto parabolic cylinder functions (PCFs), which represent the meridional structure of individual wave modes, to attain time-dependent spatial wave structures. The non-orthogonality of wave modes has yet posed a problem when attempting to...
Show moreEquatorial waves have been studied extensively due to their importance to the tropical climate and weather systems. Historically, their activity is diagnosed mainly in the wavenumber-frequency domain. Recently, many studies have projected observational data onto parabolic cylinder functions (PCFs), which represent the meridional structure of individual wave modes, to attain time-dependent spatial wave structures. The non-orthogonality of wave modes has yet posed a problem when attempting to separate data into wave fields where the waves project onto the same structure functions. We propose the development and application of a new methodology for equatorial wave expansion of instantaneous flows using the full equatorial wave spectrum. By creating a mapping from the meridional structure function amplitudes to the equatorial wave class amplitudes, we are able to diagnose instantaneous wave fields and determine their evolution. Because all meridional modes are shared by some subset of the wave classes, we require constraints on the wave class amplitudes to yield a closed system with a unique solution for all waves' spatial structures, including IG waves. A synthetic field is analyzed using this method to determine its accuracy for data of a single vertical mode. The wave class spectra diagnosed using this method successfully match the correct dispersion curves even if the incorrect depth is chosen for the spatial decomposition. In the case of more than one depth scale, waves with varying equivalent depth may be similarly identified using the dispersion curves. The primary vertical mode is the 200 m equivalent depth mode, which is that of the peak projection response. A distinct spectral power peak along the Kelvin wave dispersion curve for this value validates our choice of equivalent depth, although the possibility of depth varying with time and height is explored. The wave class spectra diagnosed assuming this depth scale mostly match their expected dispersion curves, showing that this method successfully partitions the wave spectra by calculating wave amplitudes in physical space. This is particularly striking because the time evolution, and therefore the frequency characteristics, is determined simply by a timeseries of independently-diagnosed instantaneous horizontal fields. We use the wave fields diagnosed by this method to study wave evolution in the context of the stratospheric QBO of zonal wind, confirming the continuous evolution of the selection mechanism for equatorial waves in the middle atmosphere. The amplitude cycle synchronized with the background zonal wind as predicted by QBO theory is present in the wave class fields even though the dynamics are not forced by the method itself. We have additionally identified a time-evolution of the zonal wavenumber spectrum responsible for the amplitude variability in physical space. Similar to the temporal characteristics, the vertical structures are also the result of a simple height cross-section through multiple independently-diagnosed levels.
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Date Issued: 2016
Identifier: FSU_2016SP_Barton_fsu_0071E_13099
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
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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.
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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.
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Date Issued: 2003
Identifier: FSU_migr_etd-0039
Format: Thesis

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