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Title: Balanced and Unbalanced Flow in Primitive Equation Model Simulations of Baroclinic Wave Life Cycles.
Creator: Hayes, Philip Doyle, Cunningham, Philip, Reasor, Paul, Krishnamurti, T. N., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Simulations of baroclinic wave life cycles are performed in order to illustrate the wave evolution of a cyclone and diagnose possible unbalanced flow associated with the destabilization of an upper-level jet. Development of the baroclinic wave is observed using the multilevel primitive equation Weather Research and Forecasting (WRF) model. A baroclinic system is produced with an initially balanced, zonal baroclinic jet on an f-plane, whereby the geometry of the dynamic tropopause is specified...
Show moreSimulations of baroclinic wave life cycles are performed in order to illustrate the wave evolution of a cyclone and diagnose possible unbalanced flow associated with the destabilization of an upper-level jet. Development of the baroclinic wave is observed using the multilevel primitive equation Weather Research and Forecasting (WRF) model. A baroclinic system is produced with an initially balanced, zonal baroclinic jet on an f-plane, whereby the geometry of the dynamic tropopause is specified. The change in geometry will result in different initial jet profiles. For each jet profile two numerical simulations comprised of different diffusion parameters are integrated to show the effect that the diffusion has on the simulation. The first simulation consists of a combination of weak horizontal and strong vertical diffusion, while the second simulation includes only strong horizontal diffusion, and is considered to be more consistent with real atmosphere characteristics. For each simulation, the nonlinear stage of the life cycle resembles a cyclonic wave-breaking system. Simulations where the vertical diffusion is strong tend to produce events of secondary cyclogenesis, which are not observed in the case of strong horizontal diffusion. Therefore, these secondary events are in all probability results of numerical instabilities at the triple point of the baroclinic system. The simulations with strong horizontal diffusion produce a crisper version of the baroclinic wave evolution cycle with sharper temperature gradients and deeper surface lows than the strong vertical diffusion case. Diagnostic calculations of the horizontal divergence and the residual of the nonlinear balance equation are shown in order to identify areas of unbalanced flow and subsequent inertia-gravity waves. Banded structures in the horizontal divergence field at the level of maximum wind speed suggest that the unbalanced flow is closely related to the upper level jet streak and possibly generated through geostrophic adjustment processes. The simulations with strong vertical diffusion contain less numerical noise and provide a clearer insight into the possible existence of inertia-gravity waves. A breakdown into the three main components of the residual of the nonlinear balance equation is shown in order to asses the contribution of each term towards the production of unbalanced flow, and indicates that the Laplacian term was the dominant factor as it was an order of magnitude stronger than the Jacobian and vorticity terms.
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Date Issued: 2005
Identifier: FSU_migr_etd-4192
Format: Thesis

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: 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

Title: Uncertainty in Scatterometer-Derived Vorticity.
Creator: Ford, Kelly Mcbeth, Bourassa, Mark, Reasor, Paul, Cunningham, Philip, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A more versatile and robust technique is developed for determining area averaged surface vorticity based on vector winds from the SeaWinds scatterometer on the QuikSCAT satellite. This improved technique is discussed in detail and compared to two previous studies by Sharp et al. (2002) and Gierach et al. (2007) that focused on early development of tropical systems. The error characteristics of the technique are examined in detail. Specifically, three independent sources of error are explored:...
Show moreA more versatile and robust technique is developed for determining area averaged surface vorticity based on vector winds from the SeaWinds scatterometer on the QuikSCAT satellite. This improved technique is discussed in detail and compared to two previous studies by Sharp et al. (2002) and Gierach et al. (2007) that focused on early development of tropical systems. The error characteristics of the technique are examined in detail. Specifically, three independent sources of error are explored: random observational error, truncation error and representation error. Observational errors are due to random errors in the wind observations, and determined as a worst-case estimate as a function of averaging spatial scale. The observational uncertainty in vorticity averaged for a roughly circular shape with a 100 km diameter, expressed as one standard deviation, is approximately 0.5 x 10 -5 s-1 for the methodology described herein. Truncation error is associated with the assumption of linear changes between wind vectors. For accurate results, it must be estimated on a case-by-case basis. An attempt is made to determine a lower bound of truncation errors through the use of composites of tropical disturbances. This lower bound is calculated as 10-7 s-1 for the composites, which is relatively small compared to the tropical disturbance detection threshold set at 5 x 10-5 s-1, used in an earlier study. However, in more realistic conditions, uncertainty related to truncation errors is much larger than observational uncertainty. The third type of error discussed is due to the size of the area being averaged. If the wind vectors associated with a vorticity maximum are inside the perimeter of this area (away from the edges), it will be missed. This type of error is analogous to over-smoothing. Tropical and sub-tropical low pressure systems from three months of QuikSCAT observations are used to examine this error. This error results in a bias of approximately 1.5 x 10-5 s-1 for area averaged vorticity calculated on a 100 km scale compared to vorticity calculated on a 25 km scale. The discussion of these errors will benefit future projects of this nature as well as future satellite missions.
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Date Issued: 2008
Identifier: FSU_migr_etd-4422
Format: Thesis

Title: Using Airborne Doppler Radar Data to Examine Eyewall Angular Momentum Budgets.
Creator: Fieux, Jessica L., Reasor, Paul D., Cunningham, Philip, Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A mesoscale budget analysis of absolute angular momentum (AAM) in the hurricane eyewall is presented using airborne dual-Doppler wind data from Hurricane Guillermo (1997). Multiple consecutive passes were made through the storm, allowing observed and budget-estimated changes to be directly assessed. Although the budget-estimated tendency is not in agreement with the observed tendency, the individual budget terms do show consistency with previous numerically based AAM budgets. The accuracy of...
Show moreA mesoscale budget analysis of absolute angular momentum (AAM) in the hurricane eyewall is presented using airborne dual-Doppler wind data from Hurricane Guillermo (1997). Multiple consecutive passes were made through the storm, allowing observed and budget-estimated changes to be directly assessed. Although the budget-estimated tendency is not in agreement with the observed tendency, the individual budget terms do show consistency with previous numerically based AAM budgets. The accuracy of the Doppler-derived wind field impacts the budget analysis; errors associated with the Doppler data are analyzed in depth. Aspects of the data processing and Doppler synthesis procedure that most directly impact the budget are identified (e.g., interpolation, mass continuity constraint, and sampling strategy). In order to more directly compare the Doppler-based budget with numerically based results, the Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) fifth generation non-hydrostatic Mesoscale Model (MM5) is used to perform an AAM budget analysis of a simulated hurricane. The numerically based budget is used to examine the impact of temporal resolution of the data on the budget, and to provide an additional context for examining the role of eddies in the Doppler-based budget. Consistent with recent mesoscale numerical budget studies, the eddy terms in the Doppler-based and numerically based AAM budgets are important in the eyewall and cannot be neglected. Contributions to the eddy flux convergence, and thus local changes in symmetric AAM, appear to be related to internal processes like mixing between the eye and eyewall, as well as the interaction of eyewall vorticity asymmetry with the environmental flow.
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Date Issued: 2008
Identifier: FSU_migr_etd-4462
Format: Thesis

Title: Effects of a Diurnal Sea Surface Temperature on Atmospheric Variability and Surface Fluxes.
Creator: Haman, Christine Lanier, Clayson, Carol Anne, Bourassa, Mark, Cunningham, Philip, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: The Madden-Julian Oscillation (MJO) is a coupled air-sea interaction that dominates intraseasonal variability in the tropical oceans. This mode of variability is especially important in the tropical western Pacific Ocean warm pool because this region contains the warmest sea surface temperatures (SST), largest annual precipitation, and largest latent heat release in the atmosphere, which strongly affect the global redistribution of heat, moisture, and momentum. The MJO is difficult to...
Show moreThe Madden-Julian Oscillation (MJO) is a coupled air-sea interaction that dominates intraseasonal variability in the tropical oceans. This mode of variability is especially important in the tropical western Pacific Ocean warm pool because this region contains the warmest sea surface temperatures (SST), largest annual precipitation, and largest latent heat release in the atmosphere, which strongly affect the global redistribution of heat, moisture, and momentum. The MJO is difficult to reproduce in models, and some speculate it is because of the relationship between the MJO and diurnal SST variability (e.g. Zheng et al. 2004). A single-column coupled atmosphere-ocean model (SCCM) is used to calculate and evaluate the effects of diurnal SST variability on the marine boundary layer and convection during the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) Intensive Observations Period (IOP). Results show that the use of a diurnally-varying SST as opposed to a daily-averaged SST impact the lower atmosphere by several degrees and the upper atmosphere through convection. Large-scale advective tendencies of air temperature and specific humidity can act to enhance or reduce the effects of local feedbacks resulting from diurnal warming. The absence of the diurnal SST cycle substantially impacts the transition phases of the MJO with considerable differences in low-level and mid-level cloud amount, due to changes in low-level moistening, which is essential in preconditioning the atmosphere for deep convection. These results support the hypothesis that a lack of diurnal SST variability in large-scale models could contribute to incorrect moistening during the transition phase, which is important to simulating the MJO.
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Date Issued: 2007
Identifier: FSU_migr_etd-4311
Format: Thesis

Title: Analysis and Evolution of Balance in Unstable Barotropic Jets.
Creator: Smith, Travis Allen, Cunningham, Philip, Barcilon, Albert I., Krishnamurti, T. N., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: The nature of balance in the atmosphere is of central importance to the dynamics of both the troposphere and the stratosphere, and unbalanced motions such as inertia-gravity waves play a significant role in many aspects of atmospheric behavior. In light of the importance of upper-tropospheric jets for the generation of inertia-gravity waves in the atmosphere, this study examines the evolution of unstable barotropic jets to assess the nature and evolution of balance in these features. This...
Show moreThe nature of balance in the atmosphere is of central importance to the dynamics of both the troposphere and the stratosphere, and unbalanced motions such as inertia-gravity waves play a significant role in many aspects of atmospheric behavior. In light of the importance of upper-tropospheric jets for the generation of inertia-gravity waves in the atmosphere, this study examines the evolution of unstable barotropic jets to assess the nature and evolution of balance in these features. This issue is explored using the simplest non-trivial dynamical framework in which balanced and unbalanced flows can coexist, namely the one-layer shallow water equations. In this study, numerical simulations of initially balanced zonal barotropic jets on an f plane are investigated for evidence of the breakdown of balance and the generation of inertia-gravity waves during the life cycles of the instabilities to these jets. In these simulations, the parameters of the basic-state jet (i.e., jet width and speed) are varied systematically in an attempt to elucidate the dependence of balance on the structure and dynamical evolution of the instability. The presence of unbalanced flow, either in numerical simulations or in atmospheric data, is typically inferred via various quantities that provide indirect measures of imbalance, such as the existence of strong ageostrophy, large Rossby and/or Lagrangian Rossby numbers, and large values of horizontal divergence and its material derivative. Along with evaluating these parameters in each simulation, a potential vorticity inversion method is employed to obtain the structure of balanced and unbalanced fields within each simulation. The diagnostic calculations are then compared to the potential vorticity inversion results. Contrasts and comparisons are presented for each of the simulations shown in this study. The simulations consist of an unstable barotropic wave ranging from small (i.e., O(10-1)) Rossby and Froude number to large (i.e., O(1)) Rossby and Froude number. For strong jets, neither the Rossby number nor the Froude number is small compared to unity therefore the applicability of traditional scale analysis is unclear (e.g. Haltiner and Williams, 1980) (i.e., the balance condition is no longer valid and a breakdown of balance should occur). In contrast, the results of the diagnostic calculations and potential vorticity inversions reveal that nonlinear balance is essentially valid for this particular jet profile, even though the Rossby and Froude numbers are O(1) for the strong barotropic jet. Significant inertia-gravity wave structures were not found in any of the cases shown here, which is consistent with the results obtained by several other investigators in their integrations of the shallow-water equations.
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Date Issued: 2004
Identifier: FSU_migr_etd-1666
Format: Thesis

Title: Warm Season Lightning Distributions over the Northern Gulf of Mexico Coast and Their Relation to the Mesoscale and Synoptic Scale Environments.
Creator: Stroupe, Jessica Raye, Fuelberg, Henry E., Liu, Guosheng, Cunningham, Philip, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Cloud-to-ground lightning data from the National Lightning Detection Network during the 14-year period 1989-2002 are used to create a warm season lightning climatology for the northern Gulf Coast. Days are separated into five flow regimes based on the orientation of the coastline and the low-level flow. Specifically, each day is classified into either a calm (less than 2.5 m s-1) or directional flow category based on the mean 1000-700 hPa vector wind data at Lake Charles and Slidell,...
Show moreCloud-to-ground lightning data from the National Lightning Detection Network during the 14-year period 1989-2002 are used to create a warm season lightning climatology for the northern Gulf Coast. Days are separated into five flow regimes based on the orientation of the coastline and the low-level flow. Specifically, each day is classified into either a calm (less than 2.5 m s-1) or directional flow category based on the mean 1000-700 hPa vector wind data at Lake Charles and Slidell, Louisiana. Flash densities are calculated, and maps are created for daily, hourly, and nocturnal periods. The composite 24-hour and nocturnal flash density maps indicate an east-to-west decrease in lightning over the region. Flash densities for the 24-hour period are greatest over land, with relative maxima located near the major metropolitan areas of Houston, Lake Charles, Baton Rouge, New Orleans, Biloxi, and Mobile. Flash densities during the nocturnal period are largest over the coastal waters. Land breezes, warm and shallow Gulf of Mexico waters, and advection of land-forming convection are responsible for the nighttime offshore convection. Lightning across the northern Gulf Coast depends largely on the prevailing synoptic flow. The low-level flow controls the sea breeze, the dominant forcing mechanism during the warm season. Southwest flow is the most unstable and humid of the five regimes, and it exhibits the most flashes. In this case, sea breeze induced convection is located slightly inland from the coast. Northeast flow, being the driest and most stable of the regimes, exhibits the least amount of lightning. The large-scale flow holds the sea breeze along the coastline. Flash density maxima over urban areas are examined to determine the relationship between lightning and the low-level flow. Analyses reveal that these maxima result from interactions between the prevailing flow and one or more mesoscale circulations. Urban influences such as frictional convergence, heat island effects, and air pollution also play a role in the enhancements. Geographic features and local mesoscale circulations affect lightning across the northern Gulf Coast. Geographic features, including lakes, bays, marshes, swamps, and coastline orientations, interact with the low-level flow and mesoscale circulations, such as the sea breeze and lake breezes, to produce complex lightning patterns and distributions. This climatology is useful for operational meteorologists faced with the challenge of forecasting summertime convection and its resulting lightning.
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Date Issued: 2003
Identifier: FSU_migr_etd-1532
Format: Thesis

Title: Skill of Synthetic Superensemble Hurricane Forecasts for the Canadian Maritime Provinces.
Creator: Szymczak, Heather Lynn, Krishnamurti, T. N., Cunningham, Philip, Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: The impact of tropical cyclones on Canadian Provinces is an important issue. From 1994 to 2003, fifty-five tropical cyclones entered the Canadian Hurricane Centre (CHC) Response Zone, or ~42% of all named Atlantic tropical cyclones in this ten-year period, and 2003 was the fourth consecutive year for a tropical cyclone to make landfall in Canada. The CHC forecasts all tropical cyclones that enter the CHC Response Zone and assumes the lead in forecasting once the cyclone enters the CHC Area of...
Show moreThe impact of tropical cyclones on Canadian Provinces is an important issue. From 1994 to 2003, fifty-five tropical cyclones entered the Canadian Hurricane Centre (CHC) Response Zone, or ~42% of all named Atlantic tropical cyclones in this ten-year period, and 2003 was the fourth consecutive year for a tropical cyclone to make landfall in Canada. The CHC forecasts all tropical cyclones that enter the CHC Response Zone and assumes the lead in forecasting once the cyclone enters the CHC Area of Forecast Responsibility. This study acknowledges the challenges of forecasting such tropical cyclones at extratropical latitudes. If a tropical cyclone has been declared extratropical, global models may no longer carry the cyclone, and even if it is modeled, large model errors often result. The purpose of this study is to develop a new version of the FSU hurricane superensemble with greater skill in tracking tropical cyclones, especially at extratropical latitudes. This has been achieved from the development of the synthetic superensemble. The synthetic superensemble is similar to the multi-model superensemble that is used operationally at FSU. The operational superensemble is a statistical linear regression technique that uses real-time forecasts provided by several hurricane models to construct an optimal consensus forecast. The synthetic superensemble differs from the operational version in that it uses a larger set of member models, including the regular member models, synthetic versions of these models, and the operational superensemble and its synthetic version. Synthetic member model forecast tracks are produced by a simple alteration of the original model track. The alteration consists of producing a linear best-fit line through a hurricane track and applying a Fourier curve to the linear best-fit line to artificially generate a new track shape. This synthetic superensemble is being used here to forecast hurricane tracks from the 2001, 2002, and 2003 hurricane seasons. The synthetic superensemble produced forecasts with generally less track error than its member models, the operational superensemble, and the ensemble mean. It also performed exceptionally well for several major Canadian storms including Hurricane Juan of 2003 where the synthetic superensemble outperformed the Official forecast and the operational superensemble by 425-480 km at the longest forecast hour. Forecasting challenges for each season are discussed and it was found that the synthetic superensemble produced forecasts with greatest skill in the 2003 season when there were few major changes made to member models and when member models performed at their best. Overall, this research shows that the synthetic superensemble performs consistently well and would be an asset to operational hurricane track forecasting.
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Date Issued: 2004
Identifier: FSU_migr_etd-1472
Format: Thesis

Title: An Investigation of Coherent Tropopause Disturbances Using a High Resolution Global Model.
Creator: Waller, James Scott, Cunningham, Philip, Hart, Robert, Krishnamurti, T. N., Reasor, Paul, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Coherent Tropopause Disturbances (CTD's) have been observed to play a central role in both extratropical cyclogenesis and the dynamics of jet streaks. Recent observational studies have quantified the existence of CTD's by locating potential temperature minima on a constant potential vorticity surface that is representative of the dynamic tropopause. This study applies a similar approach, but to a data set from a high-resolution global model (the Community Climate Model, Version 3)....
Show moreCoherent Tropopause Disturbances (CTD's) have been observed to play a central role in both extratropical cyclogenesis and the dynamics of jet streaks. Recent observational studies have quantified the existence of CTD's by locating potential temperature minima on a constant potential vorticity surface that is representative of the dynamic tropopause. This study applies a similar approach, but to a data set from a high-resolution global model (the Community Climate Model, Version 3). Application of an objective identification and tracking algorithm, along with several statistical calculations involving potential temperature on the 2.0 PVU surface, with statistics of outgoing longwave radiation, indicate that the CCM3 is a tool that may yield valuable insight into the dynamical interactions that determine the origin, growth and lifecycles of CTD's.
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Date Issued: 2006
Identifier: FSU_migr_etd-1335
Format: Thesis

Title: A Global and Regional Diagnostic Comparison of Air-Sea Flux Parameterizations during Episodic Events.
Creator: Moroni, David Francis, Bourassa, Mark, Chassignet, Eric, Clayson, Carol Anne, Cunningham, Philip, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Twenty turbulent flux parameterizations are compared globally and regionally with a focus on the differences associated with episodic events. The regional focus is primarily upon the Gulf Stream and Drake Passage, as these two regions contain vastly different physical characteristics related to storm and frontal passages, varieties of sea-states, and atmospheric stability conditions. These turbulent flux parameterizations are comprised of six stress-related parameterizations [i.e., Large and...
Show moreTwenty turbulent flux parameterizations are compared globally and regionally with a focus on the differences associated with episodic events. The regional focus is primarily upon the Gulf Stream and Drake Passage, as these two regions contain vastly different physical characteristics related to storm and frontal passages, varieties of sea-states, and atmospheric stability conditions. These turbulent flux parameterizations are comprised of six stress-related parameterizations [i.e., Large and Pond (1981), Large et al. (1994), Smith (1988), HEXOS (Smith et al. 1992, 1996), Taylor and Yelland (2001), and Bourassa (2006)] which are paired with a choice of three atmospheric stability parameterizations ['Neutral' assumption, Businger-Dyer (Businger 1966, Dyer 1967, Businger et al. 1971, and Dyer 1974) relations, and Beljaars-Holtslag (1991) with Benoit (1977)]. Two remaining turbulent flux algorithms are COARE version 3 (Fairall et al. 2003) and Kara et al. (2005), where Kara et al. is a polynomial curve fit approximation to COARE; these have their own separate stability considerations. The following data sets were used as a common input for parameterization: Coordinated Ocean Reference Experiment version 1.0, Reynolds daily SST, and NOAA WaveWatch III. The overlapping time period for these data sets is an eight year period (1997 through 2004). Four turbulent flux diagnostics (latent heat flux, sensible heat flux, stress, curl of the stress) are computed using the above parameterizations and analyzed by way of probability distribution functions (PDFs) and RMS analyses. The differences in modeled flux consistency are shown to vary by region and season. Modeled flux consistency is determined both qualitatively (using PDF diagrams) and quantitatively (using RMS differences), where the best consistencies are found during near-neutral atmospheric stratification. Drake Passage shows the least sensitivity (in terms of the change in the tails of PDFs) to seasonal change. Specific flux diagnostics show varying degrees of consistency between stability parameterizations. For example, the Gulf Stream's latent heat flux estimates are the most inconsistent (compared to any other flux diagnostic) during episodic and non-neutral conditions. In all stability conditions, stress and the curl of stress are the most consistent modeled flux diagnostics. Sea-state is also a very important source of modeled flux inconsistencies during episodic events for both regions.
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Date Issued: 2008
Identifier: FSU_migr_etd-2261
Format: Thesis

Title: A Chemical and Meteorological Analysis of Long-Range Transport from Africa during Austral Spring.
Creator: Morse, Danielle M., Fuelberg, Henry E., Ahlquist, Jon, Cunningham, Philip, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: During the austral spring months of September and October when biomass burning is prevalent in the Southern Hemisphere, long-range transport can move the biomass burning byproducts from southern Africa to the Pacific Basin. Meteorological data from September 1996 were used to examine the transport from Africa using forward trajectories. Long-range transport is defined as trajectories that extend from Africa eastward to at least 110°E within 10 days. Five categories were found from trajectory...
Show moreDuring the austral spring months of September and October when biomass burning is prevalent in the Southern Hemisphere, long-range transport can move the biomass burning byproducts from southern Africa to the Pacific Basin. Meteorological data from September 1996 were used to examine the transport from Africa using forward trajectories. Long-range transport is defined as trajectories that extend from Africa eastward to at least 110°E within 10 days. Five categories were found from trajectory analysis to constitute the major long-range transport pathways: zonal flow (35%) and four anticyclonic flows over Australia (5%), the western Pacific (5%), Easter Island (0.8%) and South America (0.9%). Chemical data collected during NASA's Pacific Exploratory Mission-Tropics, Phase A (PEM-Tropics A) and Transport and Atmospheric Chemistry near the Equator- Atlantic (TRACE-A) missions were studied to determine the chemical evolution of burning byproducts during the long-range transport. Photochemical decay and physical mixing with background air were both found to be important dilution processes, with estimates of physical mixing lifetimes shorter than photochemical decay lifetimes. Greater values of pollution were detected at mid-tropospheric altitudes over the Pacific Basin, suggesting that more pollution is transported to mid-levels at long ranges.
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Date Issued: 2005
Identifier: FSU_migr_etd-2241
Format: Thesis

Title: Quikscat-Derived Near-Surface Vorticity during Tropical Cyclogenesis.
Creator: Minter, Elizabeth, Reasor, Paul D., Bourassa, Mark A., Cunningham, Philip, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Traditional surface and upper-air observations are often absent over the tropical oceans. This lack of routine in-situ measurement, outside of special field programs, has limited the observational study of tropical cyclogenesis. Remote sensing from satellites, however, can provide information in regions where surface-based observing networks are not present. This study utilizes infrared satellite imagery and QuikSCAT-derived near-surface vorticity from the 2005 hurricane season in the North...
Show moreTraditional surface and upper-air observations are often absent over the tropical oceans. This lack of routine in-situ measurement, outside of special field programs, has limited the observational study of tropical cyclogenesis. Remote sensing from satellites, however, can provide information in regions where surface-based observing networks are not present. This study utilizes infrared satellite imagery and QuikSCAT-derived near-surface vorticity from the 2005 hurricane season in the North Atlantic to examine the relationship between deep convection and low-level vorticity during tropical cyclogenesis. QuikSCAT-derived cyclonic relative vorticity is identified in association with developing easterly wave disturbances tracked using NHC products and 3-hourly infrared satellite imagery. Area-averaged vorticity near mesoscale regions of convection within the easterly wave envelope is then computed. In most of the 19 cases examined, the low-level vorticity followed the convective evolution, decreasing or remaining nearly constant during periods of inactive convection and increasing as convective activity increased. A composite of North Atlantic easterly wave disturbances was constructed to characterize the average evolution of near-surface vorticity during tropical cyclogenesis. 48 hours prior to genesis, the average tropical disturbance has a region of cyclonic relative vorticity about 125 km in diameter with peak magnitude of approximately 1x10-4 s-1. During its subsequent evolution, the vorticity of the composite disturbance increases as convection increases until a tropical cyclone forms. These results are considered in the context of prior and future numerical simulations of tropical cyclogenesis.
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Date Issued: 2007
Identifier: FSU_migr_etd-2394
Format: Thesis

Title: Developing Statistical Guidance for Afternoon Lightning Activity in Portions of Two South Florida Counties.
Creator: Winarchick, Justin Marsh, Fuelberg, Henry E., Kim, Kwang Yul, Cunningham, Philip, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Statistical guidance equations are developed to determine the probability of noon to midnight lightning activity (the occurrence or non occurrence of at least one flash) in eastern Miami-Dade and Broward Counties during the warm season (May-September). The guidance assumes that the sea breeze provides the dominant forcing for afternoon convective and lightning activity. The guidance product is developed to assist Florida Power and Light Corporation personnel in deciding whether extra line...
Show moreStatistical guidance equations are developed to determine the probability of noon to midnight lightning activity (the occurrence or non occurrence of at least one flash) in eastern Miami-Dade and Broward Counties during the warm season (May-September). The guidance assumes that the sea breeze provides the dominant forcing for afternoon convective and lightning activity. The guidance product is developed to assist Florida Power and Light Corporation personnel in deciding whether extra line crews will be needed after normal business hours. Fourteen years (1989-2002) of warm season lightning data from the National Lightning Detection Network and 1200 UTC Miami radiosonde data are used to develop and test the guidance equations. The lightning data document whether lightning occurred within the areas of interest during the noon to midnight time period. The radiosonde data are used to calculate fifty-four potential predictors, including wind, moisture, stability and temperature parameters. Two persistence variables (the previous day's afternoon activity and the current day's morning activity) also are included as potential predictors. Binary logistic regression is used to relate the noon to midnight lightning activity to the pool of potential predictors. A stepwise screening procedure is used to build separate models for each month during the warm season for both counties. Deriving separate monthly models is found to improve forecast skill compared to a single warm season model. Each monthly model generally contains persistence and the wind, moisture, and stability parameters which are known to influence the strength and movement of the sea breeze and convective development. A cross-validation procedure is used to test the models on independent data and to determine the stability of the models. The cross-validation process reveals that the models are statistically stable and perform well when tested on independent data. The probability of detection, calculated from the independent testing, ranges from ~67% during May to ~90% in August, while false alarm rates range from ~30% during May to only 15% in August. Results from independent testing of the models also show that they improve on forecasts based solely on persistence. For example, the threat score for the guidance equations is ~69% versus ~61% for persistence alone. Furthermore, the hit rate improves from ~71% to ~77%. Although persistence is a powerful predictor of lightning activity in South Florida during the warm season, the guidance equations provide superior results. Days when the models produced an incorrect forecast are examined. When no lightning was forecast but occurred anyway, quartiles of lightning activity are considered. The percent of incorrect forecasts decreases from low activity days (i.e., 1st quartile days, 1-7 afternoon flashes) to high activity days (4th quartile days, >125 afternoon flashes). Thus, incorrect forecasts are least likely on the most important days. Fewer days with lightning occurrence are incorrectly forecast during July and August than during May. A similar trend is observed on days when no noon to midnight lightning was observed but had been forecast.125 afternoon flashes). Thus, incorrect forecasts are least likely on the most important days. Fewer days with lightning occurrence are incorrectly forecast during July and August than during May. A similar trend is observed on days when no noon to midnight lightning was observed but had been forecast.
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Date Issued: 2004
Identifier: FSU_migr_etd-0939
Format: Thesis

Title: PV-Induced Forcing of Gravity Waves in a Shallow Water Model.
Creator: Ward, Marshall, Cunningham, Philip, Peterson, Janet, Clayson, Carol Anne, Dewar, William K., Krishnamurti, Ruby, Program in Geophysical Fluid Dynamics, Florida State University
Abstract/Description: The influence of a geostrophically balanced or potential vorticity (PV) background flow on gravity wave propagation is examined using a rotating shallow water model. The system is analyzed in the context of a perturbative expansion that focuses on the dynamics of the resonances within the nonlinear terms of the system. The nonlinearity is reconstructed as a wave-wave interaction forcing on an otherwise undisturbed linear wavefield. The principal conclusion is that while the PV flow is...
Show moreThe influence of a geostrophically balanced or potential vorticity (PV) background flow on gravity wave propagation is examined using a rotating shallow water model. The system is analyzed in the context of a perturbative expansion that focuses on the dynamics of the resonances within the nonlinear terms of the system. The nonlinearity is reconstructed as a wave-wave interaction forcing on an otherwise undisturbed linear wavefield. The principal conclusion is that while the PV flow is generally undisturbed by the gravity wavefield, the gravity wavefield is forced by the geostrophic flow over moderate timescales. We numerically test these results for the interaction between a single geostrophic mode and a gravity wave, followed by propagation of a single gravity mode through a turbulent PV background. We find that the gravity mode energy is scattered into other modes of similar wavelength but different directions of propagation. The rate of dispersion is in agreement with resonant triad theory, where the rate depends primarily on the initial gravity wavenumber and background PV strength. These results are expected to have relevance to the propagation of coherent internal tides in the open ocean.}
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Date Issued: 2008
Identifier: FSU_migr_etd-1243
Format: Thesis

Title: Forecast Skill of the NCEP GFS Model in the Southern Hemisphere Stratosphere in 2006.
Creator: Brodowski, Christopher, Cai, Ming, Cunningham, Philip, Ahlquist, Jon, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: This study diagnoses the anomaly fields of the Southern Hemispheric stratosphere in the period from 1 January 2006 to 28 February 2007 and examines the forecasting skill of the NCEP GFS model for the Southern Hemisphere (SH) during this period. Observational and model forecast data were converted into anomaly field data in a semi-Lagrangian θ-PVLAT coordinate. The first two EOF modes of the potential vorticity (PV) anomaly in the θ-PVLAT coordinate constitute over 80% of the total variance....
Show moreThis study diagnoses the anomaly fields of the Southern Hemispheric stratosphere in the period from 1 January 2006 to 28 February 2007 and examines the forecasting skill of the NCEP GFS model for the Southern Hemisphere (SH) during this period. Observational and model forecast data were converted into anomaly field data in a semi-Lagrangian θ-PVLAT coordinate. The first two EOF modes of the potential vorticity (PV) anomaly in the θ-PVLAT coordinate constitute over 80% of the total variance. It was found that the SH stratospheric polar vortex is quite stable (with a period twice as long as its NH counterpart) and persistent, and that the NCEP GFS model forecasts exclusively dynamical processes such as the equatorial quasi-biennial oscillation (QBO) with extremely high success but possesses a cold bias in the troposphere and a warm bias in the stratosphere due to a lack of updated greenhouse gas information. Forecasting skill in the stratosphere was far higher than in the troposphere, and the second EOF modes possess higher forecast skill than the first. The good forecast skill in the stratosphere is due to the GFS's ability of capturing the slow poleward propagation of stratospheric thermal anomalies associated with the polar vortex oscillation. Overall forecast skill scores were high enough to indicate that the NCEP GFS model has great potential in stratospheric climate prediction, but the model needs timely evolving greenhouse gas information to improve further.
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Date Issued: 2008
Identifier: FSU_migr_etd-3008
Format: Thesis

Title: A Diagnostic Study of the Effects of Trough Interactions on Tropical Cyclone QPF.
Creator: Guimond, Stephen Richard, Bourassa, Mark, Hart, Robert, Cunningham, Philip, Fuelberg, Henry, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A composite study is presented analyzing the influence of upper-tropospheric troughs on the evolution of precipitation in twelve Atlantic tropical cyclones (TCs) between the years 2000 – 2005. The TRMM Multi-Satellite Precipitation Analysis (TMPA) is used to examine the enhancement of precipitation within a 24 h window centered on trough interaction (TI) time in a shear-vector relative coordinate system. Eddy angular momentum flux convergence (EFC) computed from European Centre for Medium...
Show moreA composite study is presented analyzing the influence of upper-tropospheric troughs on the evolution of precipitation in twelve Atlantic tropical cyclones (TCs) between the years 2000 – 2005. The TRMM Multi-Satellite Precipitation Analysis (TMPA) is used to examine the enhancement of precipitation within a 24 h window centered on trough interaction (TI) time in a shear-vector relative coordinate system. Eddy angular momentum flux convergence (EFC) computed from European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses is employed to objectively determine the initiation of a TI while adding insight, along with vertical wind shear, into the intensification of TC vortices. The relative roles of the dynamics (EFC and vertical wind shear) and thermodynamics (moist static energy potential) in TIs are outlined in the context of precipitation enhancement that provides quantitative insight into the "good trough"/"bad trough" paradigm. The largest precipitation rates and enhancements are found in the down-shear left quadrant of the storm, consistent with previous studies of convective asymmetries. Maximum mean enhancement values of 1.4 mm/h are found at the 200 km radius in the down-shear left quadrant. Results indicate that the largest precipitation enhancements occur with "medium" TIs; comprised of EFC values between 17 – 22 (m/s)/day and vertical wind shear Sensitivity tests on the upper vertical wind shear boundary reveal the importance of using the tropopause for wind shear computations when a TC enters mid-latitude regions. Changes in radial mean precipitation ranging from 29 – 40 % across all storm quadrants are found when using the tropopause as the upper boundary on the shear vector. Tests on the lower boundary using QuikSCAT ocean surface wind vectors expose large sensitivities on the precipitation ranging from 42 – 60 % indicating that the standard level of 850 hPa, outside of the boundary layer in most storms, is more physically reliable for computing vertical wind shear. These results should help to improve TC quantitative precipitation forecasting (QPF) as operational forecasters routinely rely on crude statistical methods and rules of thumb for forecasting TC precipitation.
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Date Issued: 2007
Identifier: FSU_migr_etd-3922
Format: Thesis

Title: Modified JMA ENSO Index and Its Improvements to ENSO Classification.
Creator: Keeling, Travis B., O’Brien, James J., Cunningham, Philip, Cai, Ming, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: El Nino-Southern Oscillation (ENSO) is a widely known phenomenon that affects many areas including the southeast United States. Over the southeast U.S. the Japan Meteorological Agency (JMA) ENSO index was modified to establish better classifications. In order to properly understand the effects of ENSO on this location a new approach was needed. Spatial resolution was improved by utilization of the PRISM dataset. PRISM provided monthly precipitation and temperature data over the contiguous US...
Show moreEl Nino-Southern Oscillation (ENSO) is a widely known phenomenon that affects many areas including the southeast United States. Over the southeast U.S. the Japan Meteorological Agency (JMA) ENSO index was modified to establish better classifications. In order to properly understand the effects of ENSO on this location a new approach was needed. Spatial resolution was improved by utilization of the PRISM dataset. PRISM provided monthly precipitation and temperature data over the contiguous US at 4 km resolution. Temporal resolution was improved by disregarding the traditional JMA definition of an ENSO year. The new definition requires six consecutive months of 0.5°C anomalies or larger to be listed as an ENSO event. By utilization of this definition, the ENSO index was modified to a monthly index from a yearly index. Many ENSO events begin in the summer months and end before the preceding September, therefore, an adoption of a monthly index is justified. Although several of the effects vary widely over the domain, there are a few prevalent patterns of ENSO effects. During warm phase, from November-April, wet conditions are seen in the coastal areas. July and August are both dry. From fall to spring, Florida and the Atlantic Coast are basically dry, however; the Mississippi River Valley doesn't appear wet as previous studies have indicted. Patterns of temperatures across the southeast are less variable than the precipitation. Differences between the ModJMA and JMA can be seen in several months, especially during late spring and early autumn. This result is not surprising based on the rigid definition of the JMA index. An interesting result presented itself throughout the study. Individual tropical storms can be identified with the increased resolution PRISM data provides. A state by state breakdown of the ModJMA conclusions provides regional summaries. The ModJMA better classifies ENSO periods and leads to a more precise impact of ENSO over the southeast United States.
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Date Issued: 2009
Identifier: FSU_migr_etd-3246
Format: Thesis

Title: The Changing Geomagnetic Field from the Ionosphere to the Core-Mantle Boundary.
Creator: Mozzoni, David T. (David Theodore), Van Winkle, David, Cunningham, Philip, Berg, Bernd, Cain, Joseph, Riley, Mark, Department of Physics, Florida State University
Abstract/Description: In this study two aspects of the geomagnetic field have been investigated. The first part focuses on perturbations of the external field, as seen by the CHAMP satellite and predicted by the Thermosphere-Ionosphere Electrodynamic General Circulation Model, for the purpose of helping to separate out ionospheric sources from the ambient geomagnetic field using a physics based approach. Part two looks at variations of the internal field through an examination of the South Atlantic Anomaly. The...
Show moreIn this study two aspects of the geomagnetic field have been investigated. The first part focuses on perturbations of the external field, as seen by the CHAMP satellite and predicted by the Thermosphere-Ionosphere Electrodynamic General Circulation Model, for the purpose of helping to separate out ionospheric sources from the ambient geomagnetic field using a physics based approach. Part two looks at variations of the internal field through an examination of the South Atlantic Anomaly. The NCAR Thermosphere-Ionosphere Electrodynamic General Circulation Model (TIE-GCM) is a self-consistent, global, atmospheric model that can be used to estimate magnetic perturbations at satellite altitude. These computed perturbations can then be compared with the magnetic vector data provided by low-earth orbiting satellites. Analogous CHAMP magnetic vector residuals were computed for these intervals using the CHAOS model to remove the core and crustal geomagnetic contributions. Under various input parameters, the TIE-GCM predictions were compared with the CHAMP residuals on an orbit by orbit basis demonstrating a reasonable agreement between the TIE-GCM estimates and the CHAMP residuals in non-polar, dayside regions (±50° magnetic latitude). Although no clear component or temporal correlation was discerned, evidence showing overall residual decrease in the comparisons presents the possibility of using the TIE-GCM to preprocess geomagnetic data for main field modeling purposes. A group of spherical harmonic field test models, developed utilizing this correction, verify the feasibility of this application. Variations of the internal field are investigated through study of the South Atlantic Anomaly, a region of low geomagnetic field measured at the Earth's surface. The time evolution of this feature is tracked at the surface over the last 400 years. Subsequently, its associations with the axial dipole moment and radial geomagnetic flux are examined at the core-mantle boundary, revealing in the process, a possible link between total unsigned flux and geomagnetic jerks.
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Date Issued: 2007
Identifier: FSU_migr_etd-2213
Format: Thesis

Title: Observational Analyses and Idealized Numerical Simulations of African Wave Dynamics.
Creator: Smith, Travis Allen, Cunningham, Philip, Dewar, William, Hart, Robert, Nicholson, Sharon E., Krishnamurti, T. N., Department of Earth, Ocean and Atmospheric Sciences, Florida...
Show moreSmith, Travis Allen, Cunningham, Philip, Dewar, William, Hart, Robert, Nicholson, Sharon E., Krishnamurti, T. N., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: The role of the Tropical Easterly Jet (TEJ) in West African rainfall climatology has received little attention in the research community to date. Therefore, this dissertation will examine the instabilities and wave activity associated with the TEJ and their implications regarding interannual rainfall variability over western Africa. First, the instability of the TEJ is examined using potential vorticity (PV) concepts to contrast wet and dry years in West Africa. Analyses of the meridional PV...
Show moreThe role of the Tropical Easterly Jet (TEJ) in West African rainfall climatology has received little attention in the research community to date. Therefore, this dissertation will examine the instabilities and wave activity associated with the TEJ and their implications regarding interannual rainfall variability over western Africa. First, the instability of the TEJ is examined using potential vorticity (PV) concepts to contrast wet and dry years in West Africa. Analyses of the meridional PV gradient indicate an abrupt shift in both location and magnitude of the instability associated with the TEJ during the transition from wet to dry years in the Sahel. Additionally, the signs of the climatological anomalies of PV at the TEJ level strongly reflect the four primary modes (wet, dry, wet dipole, and dry dipole) of interannual rainfall variability in West Africa. Several examples of PV perturbation analyses at the TEJ level confirm that the upper-level development of African Easterly Waves (AEWs) differs considerably between the two periods. These results support recent observations and modeling studies that suggest that the interaction between the TEJ and the African Easterly Jet (AEJ) plays an important role in the development and structure of AEWs. In addition to the observational study, a multi-layer primitive equation model is utilized to examine easterly wave activity and vertical motion patterns based on the juxtaposition of the three primary jets located over western Africa. Idealized simulations based on the basic states of the low-level westerly jet (LLWJ), African Easterly Jet (AEJ), and the Tropical Easterly Jet (TEJ) for several anomalously wet and dry years in the Sahel are studied. Results are compared to several linearized GCM simulations that are initialized with NCEP observational data. Results show that the location, intensity, and scale of wave perturbations are sensitive to the position and intensity of the jets. Vertical motion patterns also indicate that maximum upward motion is generally located between the cores of the AEJ and TEJ and was more intense in the wet years. These results generally agree with observational and other modeling studies, further emphasizing that jet position and intensity are important factors in determining interannual rainfall variability across western Africa
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Date Issued: 2008
Identifier: FSU_migr_etd-1658
Format: Thesis

Title: Evolution of the Organization of Convection and Scale Interactions during Hurricane Genesis.
Creator: Watson, Leela Ramaswamy, Krishnamurti, T. N., Krishnamurti, Ruby, Cunningham, Philip, Liu, Guosheng, Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida...
Show moreWatson, Leela Ramaswamy, Krishnamurti, T. N., Krishnamurti, Ruby, Cunningham, Philip, Liu, Guosheng, Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: This study will examine scale interactions and energy transformations that occur during hurricane genesis. A high-resolution mesoscale model that uses initial and boundary conditions obtained from the National Centers for Environmental Prediction (NCEP) Global Final Tropospheric Analyses and that produces a reasonable simulation on hurricane genesis will be employed. We will first explore the organization of convection during hurricane genesis to establish which scales are evolving and to...
Show moreThis study will examine scale interactions and energy transformations that occur during hurricane genesis. A high-resolution mesoscale model that uses initial and boundary conditions obtained from the National Centers for Environmental Prediction (NCEP) Global Final Tropospheric Analyses and that produces a reasonable simulation on hurricane genesis will be employed. We will first explore the organization of convection during hurricane genesis to establish which scales are evolving and to determine which wavenumbers constitute the hurricane scale. Next, complete energy budgets during hurricane genesis will be examined. This is aimed at sorting out energy flow during hurricane genesis. The framework of the study is based on the seminal papers by Saltzman (1957, 1970) on atmospheric energetics in the wavenumber domain. A complete energy budget includes examination of the generation of available potential energy, conversion from available potential energy to eddy kinetic energy, the rate of change of kinetic energy due to nonlinear triad interactions, the rate of change of potential energy due to nonlinear triad interactions, zonal to waves flow of kinetic energy, and zonal to waves flow of potential energy. The main findings of this study are that individual cloud elements and cloud clusters are evolving into larger scale (symmetric) clusters around the eye of the hurricane and that a hurricane's scale can be described by wavenumbers 0, 1, and 2. The largest contributor to the energy exchange was found to be both of the in-scale quadratic nonlinearities, particularly the baroclinic conversion from available potential energy to kinetic energy. The transfer of energy between the different scales are small compared to the in-scale energy exchanges. The generation of available potential energy for the hurricane scale increases during hurricane genesis indicating the organization of clouds along the hurricane scale. The conversion of available potential energy to eddy kinetic energy mirrors the generation of available potential energy and indicates that the warm core of the storm is building up. In particular, it was found that conversion to KE due to vertical overturnings was important on the cloud scale during the formative stage of the hurricane. By the hurricane stage, the cloud scales became less important while the largest conversion occurred among the mean. The general pattern is for the mean and the large-scale asymmetries to lose available potential energy to the cloud scales indicating a down-gradient sensible heat flux. The kinetic energy exchanges between the different scales tend to be slightly smaller than the exchanges of available potential energy and are more variable. During the formative stage the general pattern is for the mean to lose kinetic energy to the large-scale asymmetries. By the hurricane stage, the exchanges between the mean and the large-scale asymmetries are similar in magnitude, but the patterns are inconsistent. However, it was found that the cloud scales receive the bulk of the KE during the hurricane stage.
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Date Issued: 2006
Identifier: FSU_migr_etd-1233
Format: Thesis

Meteorology (19)	+ -
Atmospheric sciences (2)	+ -
Oceanography (2)	+ -
Geophysics (1)	+ -
Physics (1)	+ -

Cunningham, Philip (21)	+ -
Florida State University (21)	+ -
Department of Earth, Ocean and Atmospheric Sciences (19)	+ -
Krishnamurti, T. N. (8)	+ -
Hart, Robert (7)	+ -

Bourassa, Mark (4)	+ -
Clayson, Carol Anne (3)	+ -
Fuelberg, Henry E. (3)	+ -
Reasor, Paul (3)	+ -
Ahlquist, Jon (2)	+ -
Cai, Ming (2)	+ -
Krishnamurti, Ruby (2)	+ -
Liu, Guosheng (2)	+ -
Reasor, Paul D. (2)	+ -
Smith, Travis Allen (2)	+ -
Axe, Lizabeth Marie (1)	+ -
Barcilon, Albert I. (1)	+ -
Berg, Bernd (1)	+ -
Bourassa, Mark A. (1)	+ -
Brodowski, Christopher (1)	+ -
Cain, Joseph (1)	+ -
Chassignet, Eric (1)	+ -
Cocke, Steven (1)	+ -
Department of Physics (1)	+ -
Dewar, William (1)	+ -
Dewar, William K. (1)	+ -
Evans, Allen Clark (1)	+ -
Fieux, Jessica L. (1)	+ -
Ford, Kelly Mcbeth (1)	+ -
Fuelberg, Henry (1)	+ -

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