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Title: An Absolute Angular Momentum Based Analytical Model for Tropical Cyclone Radial Wind Profiles.
Creator: Yan, Ruikai, Cai, Ming, Niu, Xufeng, Chagnon, Jeffrey M., Speer, Kevin G. (Kevin George), Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and...
Show moreYan, Ruikai, Cai, Ming, Niu, Xufeng, Chagnon, Jeffrey M., Speer, Kevin G. (Kevin George), Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: The ability to construct radial wind profiles of tropical cyclones (TC) from limited observations is crucial to the initialization of TC simulations and predictions. A minimum requirement for constructing a reasonable radial wind profile is a high skill in estimating one of the four TC characteristic parameters, namely maximum wind speed (Vmax), radius of maximum wind speed (rmax), 17 ms−1 wind speed (V17), and radius of 17 ms−1 wind (r17) from the other three. In this study, we put froth an...
Show moreThe ability to construct radial wind profiles of tropical cyclones (TC) from limited observations is crucial to the initialization of TC simulations and predictions. A minimum requirement for constructing a reasonable radial wind profile is a high skill in estimating one of the four TC characteristic parameters, namely maximum wind speed (Vmax), radius of maximum wind speed (rmax), 17 ms−1 wind speed (V17), and radius of 17 ms−1 wind (r17) from the other three. In this study, we put froth an absolute angular momentum (AAM) based analytical model for inferring the radial profile beyond the rmax from observations of these four parameters. An observed AAM loss L is defined as the ratio of the observed AAM at r17 to that at rmax. We parameterize the observed AAM loss L as an analytical function of these four parameters and environmental factors. The combination of analytical expressions of the AAM loss L and the AAM at r17 and rmax, gives us the analytical model. This observation-physics model allows us to construct radial profiles of TCs under four different configurations from observations of these four parameters. Specifically, we can use Vmax and rmax as inputs for solving (a) the tangential velocity profile of a TC from rmax to r17 or (b) the TC's radius for a given tangential velocity from Vmax to V17. Alternatively, we can use V17 and r17 as inputs for solving (c) the tangential velocity profile of a TC from r17 to rmax or (d) the TC's radius for a given tangential velocity from V17 to Vmax. This enables us to acquire radial wind profiles when one of the four parameters is not available in observations. The degree of consistency of (a) versus (c) and (b) versus (d) is an indicator of the robustness of the model. We evaluate the skill of our model using 4491 records of 197 named TCs derived from the Extended Best Track Dataset for the period of 1998-2016, and find that the mean errors in estimating Vmax, rmax, V17, and r17 are, respectively, 5.95 m/s, 25.37 km, 3.33 m/s, and 57.67 km. The proposed model has several advantages over widely recognized existing TC wind profile models. Most empirical models, for example, are designed to construct radial wind profiles in only one of the four configurations. While other physics-based models have mean errors in Vmax, rmax, and r17 that are larger by several factors. Furthermore, our model can yield physically realistic radial wind profiles and solutions of TC characteristic parameters (meaning that for radial wind profiles, wind velocity decreases monotonically from rmax to r17, and for solutions, Vmax > V17 > 0 and r17 > rmax > 0) for all 4491 TC records, regardless of which of the four configurations is chosen. For more than 10% of the TC records, however, other physics-based models have radial wind profiles that are discrete or increases from the inside to outside, and have solutions that either do not exist or are not physical under certain configurations.
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Date Issued: 2019
Identifier: 2019_Summer_Yan_fsu_0071E_15321
Format: Thesis

Title: On the Structure and Frequency of Secondary Eyewall Formation in HWRF Simulations of Tropical Cyclone Harvey (2017).
Creator: Di Catarina, Federico, Chagnon, Jeffrey M., Hart, Robert E., Sura, Philip, Florida State University, College of Arts and Sciences, Department of Earth, Ocean and Atmospheric...
Show moreDi Catarina, Federico, Chagnon, Jeffrey M., Hart, Robert E., Sura, Philip, Florida State University, College of Arts and Sciences, Department of Earth, Ocean and Atmospheric Science
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Abstract/Description: Hurricane Harvey (2017) spawned from a westward propagating tropical wave in the Atlantic and then tracked across the southern Caribbean Sea, the Yucatán Peninsula, and lastly over the Gulf of Mexico, where it quickly intensified into a category 4 (on the Saffir-Simpson Scale) tropical cyclone. As a mature hurricane, Harvey underwent an eyewall replacement cycle which led to structural and intensity changes hours before making landfall over the Texas central coast. This study investigates the...
Show moreHurricane Harvey (2017) spawned from a westward propagating tropical wave in the Atlantic and then tracked across the southern Caribbean Sea, the Yucatán Peninsula, and lastly over the Gulf of Mexico, where it quickly intensified into a category 4 (on the Saffir-Simpson Scale) tropical cyclone. As a mature hurricane, Harvey underwent an eyewall replacement cycle which led to structural and intensity changes hours before making landfall over the Texas central coast. This study investigates the structure and frequency of secondary eyewalls in 20 forecast simulations of Tropical Cyclone Harvey (2017) as produced by the 2017 operational Hurricane Weather Research and Forecast (HWRF) System. To understand the predictability of secondary eyewalls, the secondary eyewall-producing simulations must be distinguished from the non-secondary eyewall-producing simulations. Thus, a diagnostic method of subjectively detecting secondary eyewalls in forecast data is developed. The diagnostic method identifies specific secondary eyewall traits that have been studied and documented in literature. The results show that most of the simulations (~80%) produce a secondary eyewall. While the all secondary eyewall-producing simulations are initialized over the ocean, the unsuccessful simulations, on the other hand, are initialized over or just west of the Yucatán Peninsula. To study the relationship between land-storm interaction and secondary eyewall simulation, a comparison is made between the successful simulations initialized over the Caribbean Sea (which tracked over the Yucatán Peninsula) and the unsuccessful runs. For both sets of simulations, the effect of land-storm interaction led to temporary storm weakening while over the Yucatán Peninsula. However, this interaction has respectively a greater negative effect on vortex spin-up and organization on those simulations initialized over land. A comparison between the over land evolution of a non-SE producing and aSE-producing simulation is made. The results show that both storms maintain a similar dynamic structure as they move west over the Yucatán Peninsula. However, the SE-producing simulation is in a more favorable thermodynamic environment with higher RH values above the storms and more convective activity near its center when compared to the non-SE producing simulation. Based on these results, it is speculated that deep moist convective feedback processes enhanced by a thermodynamically favorable conditions within and near the Caribbean Sea initialized storms act as an additional intensification mechanism which lacks in the over land initialized storms. The relatively drier air mass and less convective activity associated with the land simulations produces a less favorable environment and limits the intensification rate of these storms over once over water. It is speculated that slower intensification rates inhibit these storms from reaching an adequate TC intensity and structure conducive for SEF before making landfall over Texas/Mexico and weakening.
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Date Issued: 2018
Identifier: 2018_Fall_DiCatarina_fsu_0071N_14783
Format: Thesis

Title: Improving Satellite-Based Snowfall Estimation: A New Method for Classifying Precipitation Phase and Estimating Snowfall Rate.
Creator: Sims, Elizabeth M., Liu, Guosheng, Meyer-Baese, Anke, Bourassa, Mark Allan, Cai, Ming, Sura, Philip, Florida State University, College of Arts and Sciences, Department of Earth,...
Show moreSims, Elizabeth M., Liu, Guosheng, Meyer-Baese, Anke, Bourassa, Mark Allan, Cai, Ming, Sura, Philip, Florida State University, College of Arts and Sciences, Department of Earth, Ocean and Atmospheric Science
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Abstract/Description: In order to study the impact of climate change on the Earth's hydrologic cycle, global information about snowfall is needed. To achieve global measurements of snowfall over both land and ocean, satellites are necessary. While satellites provide the best option for making measurements on a global scale, the task of estimating snowfall rate from these measurements is a complex problem. Satellite-based radar, for example, measures effective radar reflectivity, Ze, which can be converted to...
Show moreIn order to study the impact of climate change on the Earth's hydrologic cycle, global information about snowfall is needed. To achieve global measurements of snowfall over both land and ocean, satellites are necessary. While satellites provide the best option for making measurements on a global scale, the task of estimating snowfall rate from these measurements is a complex problem. Satellite-based radar, for example, measures effective radar reflectivity, Ze, which can be converted to snowfall rate, S, via a Ze-S relation. Choosing the appropriate Ze-S relation to apply is a complicated problem, however, because quantities such as particle shape, size distribution, and terminal velocity are often unknown, and these quantities directly affect the Ze-S relation. Additionally, it is important to correctly classify the phase of precipitation. A misclassification can result in order-of-magnitude errors in the estimated precipitation rate. Using global ground-based observations over multiple years, the influence of different geophysical parameters on precipitation phase is investigated, with the goal of obtaining an improved method for determining precipitation phase. The parameters studied are near-surface air temperature, atmospheric moisture, low-level vertical temperature lapse rate, surface skin temperature, surface pressure, and land cover type. To combine the effects of temperature and moisture, wet-bulb temperature, instead of air temperature, is used as a key parameter for separating solid and liquid precipitation. Results show that in addition to wet-bulb temperature, vertical temperature lapse rate also affects the precipitation phase. For example, at a near-surface wet-bulb temperature of 0°C, a lapse rate of 6°C km-1 results in an 86 percent conditional probability of solid precipitation, while a lapse rate of -2°C km-1 results in a 45 percent probability. For near-surface wet-bulb temperatures less than 0°C, skin temperature affects precipitation phase, although the effect appears to be minor. Results also show that surface pressure appears to influence precipitation phase in some cases, however, this dependence is not clear on a global scale. Land cover type does not appear to affect precipitation phase. Based on these findings, a parameterization scheme has been developed that accepts available meteorological data as input, and returns the conditional probability of solid precipitation. Ze-S relations for various particle shapes, size distributions, and terminal velocities have been developed as part of this research. These Ze-S relations have been applied to radar reflectivity data from the CloudSat Cloud Profiling Radar to calculate the annual mean snowfall rate. The calculated snowfall rates are then compared to surface observations of snowfall. An effort to determine which particle shape best represents the type of snow falling in various locations across the United States has been made. An optimized Ze-S relation has been developed, which combines multiple Ze-S relations in order to minimize error when compared to the surface snowfall observations. Additionally, the resulting surface snowfall rate is compared with the CloudSat standard product for snowfall rate.
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Date Issued: 2017
Identifier: FSU_2017SP_Sims_fsu_0071E_13720
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: WRF Simulations of Water Vapor Content for TC Ingrid (September 2013).
Creator: Allison, Thomas Daniel, Fuelberg, Henry E., Hart, Robert E. (Robert Edward), Misra, Vasubandhu, Holmes, Christopher D., Florida State University, College of Arts and Sciences,...
Show moreAllison, Thomas Daniel, Fuelberg, Henry E., Hart, Robert E. (Robert Edward), Misra, Vasubandhu, Holmes, Christopher D., Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: Atmospheric water vapor is a potent greenhouse gas, and its variations in the upper troposphere and lower stratosphere (UTLS) have important climate impacts. The water vapor budget of tropical cyclones (TCs) and their impact on the UTLS remain understudied. This paper describes high-resolution simulations of TC Ingrid during September 2013 using the Weather Research and Forecasting (WRF) model to calculate the water vapor budget. Using Ingrid as an example provides a better understanding of...
Show moreAtmospheric water vapor is a potent greenhouse gas, and its variations in the upper troposphere and lower stratosphere (UTLS) have important climate impacts. The water vapor budget of tropical cyclones (TCs) and their impact on the UTLS remain understudied. This paper describes high-resolution simulations of TC Ingrid during September 2013 using the Weather Research and Forecasting (WRF) model to calculate the water vapor budget. Using Ingrid as an example provides a better understanding of water vapor transport into the UTLS by TCs, helping to answer a question posed during NASA’s Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling through Regional Surveys (SEAC4RS), specifically whether water vapor transport in TCs hydrates or dehydrates the UTLS. Our WRF simulations of TC Ingrid closely correspond to the National Hurricane Center’s Best Track data. We also evaluate model results of the water vapor budget with in situ airborne data of Ingrid collected during the SEAC4RS mission. Satellite imagery also is used to validate the simulated structure of Ingrid. We show spatial and temporal changes of UTLS water vapor throughout Ingrid's lifecycle to determine whether and how TCs hydrate or dehydrate the UTLS. Results show that TCs do transport large quantities of water vapor into the UTLS, and overshooting deep convection is an especially potent transport method. The paper sheds light on mechanisms that inject water vapor into the UTLS and on the widespread horizontal and vertical transports of water vapor within TCs.
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Date Issued: 2016
Identifier: FSU_FA2016_Allison_fsu_0071N_13632
Format: Thesis

Title: Sea-Ice, Clouds and Atmospheric Conditions in the Arctic and Their Interactions as Derived from a Merged C3M Data Product.
Creator: Nag, Bappaditya, Cai, Ming, Tam, Christopher K. W., Clarke, Allan J., Liu, Guosheng, Speer, Kevin G. (Kevin George), Florida State University, College of Arts and Sciences,...
Show moreNag, Bappaditya, Cai, Ming, Tam, Christopher K. W., Clarke, Allan J., Liu, Guosheng, Speer, Kevin G. (Kevin George), Florida State University, College of Arts and Sciences, Program in Geophysical Fluid Dynamics
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Abstract/Description: The polar regions of the world constitute an important sector in the global energy balance. Among other effects responsible for the change in the sea-ice cover like ocean circulation and ice-albedo feedback, the cloud-radiation feedback also plays a vital role in modulation of the Arctic environment. However the annual cycle of the clouds is very poorly represented in current global circulation models. This study aimed to explore the atmospheric conditions in the Arctic on an unprecedented...
Show moreThe polar regions of the world constitute an important sector in the global energy balance. Among other effects responsible for the change in the sea-ice cover like ocean circulation and ice-albedo feedback, the cloud-radiation feedback also plays a vital role in modulation of the Arctic environment. However the annual cycle of the clouds is very poorly represented in current global circulation models. This study aimed to explore the atmospheric conditions in the Arctic on an unprecedented spatial coverage spanning 70°N to 80°N through the use of a merged data product, C3MData (derived from NASA's A-Train Series). The following three topics provide outline on how this dataset can be used to accomplish a detailed analysis of the Arctic environment and provide the modelling community with first information to update their models aimed at better forecasts. (1)The three properties of the Arctic climate system to be studied using the C3MData are sea-ice, clouds, and the atmospheric conditions. The first topic is to document the present states of the three properties and also their time evolutions or their seasonal cycles. (2)The second topic is aimed at the interactions or the feedbacks processes among the three properties. For example, the immediate alteration in the fluxes and the feedbacks arising from the change in the sea-ice cover is investigated. Seasonal and regional variations are also studied. (3)The third topics is aimed at the processes in native spatial resolution that drive or accompany with sea ice melting and sea ice growth. Using a composite approach based on a classification due to surface type, it is found that limitation of the water vapour influx from the surface due to change in phase at the surface featuring open oceans or marginal sea-ice cover to complete sea-ice cover is a major determinant in the modulation of the atmospheric moisture. The impact of the cloud-radiative effects in the Arctic is found to vary with sea-ice cover and seasonally. The effect of the marginal sea-ice cover becomes more and more pronounced in the winter. The seasonal variation of the dependence of the atmospheric moisture on the surface and the subsequent feedback effects is controlled by the atmospheric stability measured as a difference between the potential temperature at the surface and the 700hPa level. A regional analysis of the same suggests that most of the depiction of the variations observed is contributed from the North Atlantic region.
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Date Issued: 2016
Identifier: FSU_2016SU_Nag_fsu_0071E_13367
Format: Thesis

Title: Development and Evolution of Convective Bursts in WRF Simulations of Hurricanes Dean (2007) and Bill (2009).
Creator: Hazelton, Andrew Todd, Hart, Robert E. (Robert Edward), Chiorescu, Irinel, Bourassa, Mark Allan, Fuelberg, Henry E., Liu, Guosheng, Rogers, Robert Fulton, Florida State...
Show moreHazelton, Andrew Todd, Hart, Robert E. (Robert Edward), Chiorescu, Irinel, Bourassa, Mark Allan, Fuelberg, Henry E., Liu, Guosheng, Rogers, Robert Fulton, Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: Understanding and predicting the inner-core structure and intensity change of tropical cyclones (TCs) remains one of the biggest challenges in tropical meteorology. This study addresses this challenge by investigating the formation, structure, and intensity changes resulting from localized strong updrafts in TCs known as convective bursts (CBs). The evolution of CBs are analyzed in high-resolution simulations of two hurricanes (Dean 2007 and Bill 2009) using the Weather Research and...
Show moreUnderstanding and predicting the inner-core structure and intensity change of tropical cyclones (TCs) remains one of the biggest challenges in tropical meteorology. This study addresses this challenge by investigating the formation, structure, and intensity changes resulting from localized strong updrafts in TCs known as convective bursts (CBs). The evolution of CBs are analyzed in high-resolution simulations of two hurricanes (Dean 2007 and Bill 2009) using the Weather Research and Forecasting (WRF) model. The simulations are able to capture the observed track and peak intensity of the TCs. With Dean, there is a slight lag between the simulated intensification and actual intensification, and the extreme rate of RI is not fully captured. However, the cycle of intensification, weakening, and re-intensification observed in both TCs is captured in the simulations, and appears to be due to a combination of internal dynamics and the surrounding environmental conditions. CBs are identified based on the 99th percentile of eyewall vertical velocity (over the layer from z = 6-12 km) in each simulation (8.4 m s-1 for Dean, 5.4 m s-1 for Bill). The highest density of CBs is found in the downshear-left quadrant, consistent with prior studies. The structure of the CBs is analyzed by comparing r-z composites of azimuths with CBs and azimuths without CBs, using composite figures and statistical comparisons. The CB composites show stronger radial inflow in the lowest 0-2 km, and stronger radial outflow from the eye to the eyewall in the 2-4 km layer. The CB composites also have stronger low-level vorticity than the non-CBs, potentially due to eyewall mesovortices. The analysis of individual CBs also confirms the importance of the eye-eyewall exchange in CB development, potentially by providing buoyancy, as parcel trajectories show that many parcels are flung outward from the eye and rapidly ascend in the CBs, with as much as 500 J/kg of CAPE along the parcel path. In addition, the location of radial convergence seems to play a key role in governing the radial location of CBs. Inner-core CBs seem to be associated with local convergence maxima in the eyewall, while CBs outside the radius of maximum winds (RMW) are associated with convergence maxima due to bands and/or secondary eyewalls. Analysis of intensity change in the simulations shows that there are more inner-core CBs during times when the TCs are intensifying, while weakening/steady times appear to be associated with more CBs outside the radius of maximum wind (RMW), consistent with observational studies and theoretical work. However, times when the TC has already been intensifying and continues to do so have more CBs than times when the TC has been weakening but then intensifies. This suggests that CB development may not always be predictive, but rather may sometimes occur as a result of ongoing intensification. On the other hand, rapid intensification (RI) in the simulations is found to be associated with an even higher density of CBs inside the RMW than slower intensification. Lag correlations between CBs and intensity are calculated to investigate the time of the intensity response to CB development. These calculations reveal a broad peak in correlation, with the CBs tending to lead pressure falls by 0-3 hours. These results confirm the notion that convective heating inside the RMW is favorable for intensification. The findings from this analysis show that eyewall CBs are driven by asymmetric dynamical processes in the inner-core region of TCs, both in and above the TC boundary layer. In addition, the relationship between CB development and intensity change is indeed positive, sometimes in a predictive sense, and at other times while intensity change is ongoing.
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Date Issued: 2016
Identifier: FSU_2016SP_Hazelton_fsu_0071E_13072
Format: Thesis

Title: WRF Nested Large-Eddy Simulations of Deep Convection during SEAC4RS.
Creator: Heath, Nicholas Kyle, Fuelberg, Henry E., Wiedenhöver, Ingo, Hart, Robert E. (Robert Edward), Bourassa, Mark Allan, Misra, Vasubandhu, Turk, Francis J., Florida State University...
Show moreHeath, Nicholas Kyle, Fuelberg, Henry E., Wiedenhöver, Ingo, Hart, Robert E. (Robert Edward), Bourassa, Mark Allan, Misra, Vasubandhu, Turk, Francis J., Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: Deep convection is an important component of atmospheric circulations that affects many aspects of weather and climate. Therefore, improved understanding and realistic simulations of deep convection are critical to both operational and climate forecasts. Large-eddy simulations (LESs) often are used with observations to enhance understanding of convective processes. This study develops and evaluates a nested-LES method using the Weather Research and Forecasting (WRF) model. Our goal is to...
Show moreDeep convection is an important component of atmospheric circulations that affects many aspects of weather and climate. Therefore, improved understanding and realistic simulations of deep convection are critical to both operational and climate forecasts. Large-eddy simulations (LESs) often are used with observations to enhance understanding of convective processes. This study develops and evaluates a nested-LES method using the Weather Research and Forecasting (WRF) model. Our goal is to evaluate the extent to which the WRF nested-LES approach is useful for studying deep convection during a real-world case. The method was applied on 2 September 2013, a day of continental convection having a robust set of ground and airborne data available for evaluation. A three domain mesoscale WRF simulation is run first. Then, the finest mesoscale output (1.35 km grid length) is used to separately drive nested-LES domains with grid lengths of 450 and 150 m. Results reveal that the nested-LES approach reasonably simulates a broad spectrum of observations, from reflectivity distributions to vertical velocity profiles, during the study period. However, reducing the grid spacing does not necessarily improve results for our case, with the 450 m simulation outperforming the 150 m version. We find that simulated updrafts in the 150 m simulation are too narrow to overcome the negative effects of entrainment, thereby generating convection that is weaker than observed. Increasing the sub-grid mixing length in the 150 m simulation leads to deeper, more realistic convection, but comes at the expense of delaying the onset of the convection. Overall, results show that both the 450 m and 150 m simulations are influenced considerably by the choice of sub-grid mixing length used in the LES turbulence closure. Finally, the simulations and observations are used to study the processes forcing strong midlevel cloud-edge downdrafts that were observed on 2 September. Results suggest that these downdrafts are forced by evaporative cooling due to mixing near cloud edge and by vertical perturbation pressure gradient forces acting to restore mass continuity around neighboring updrafts. We conclude that the WRF nested-LES approach provides an effective method for studying deep convection for our real-world case. The method can be used to provide insight into physical processes that are important to understanding observations. The WRF nested-LES approach could be adapted for other case studies in which high-resolution observations are available for validation.
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Date Issued: 2015
Identifier: FSU_2015fall_Heath_fsu_0071E_12917
Format: Thesis

Title: Examining Shifts in Warm-Season Near-Surface Moisture Trends in Florida.
Creator: Swearingen, Aaron D., Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: Warm-season (1 June–31 August) near-surface moisture trends have been examined across Florida. Data was used from 86 National Weather Service cooperative stations, 24 NWS first-order stations, and the European Centre for Medium-Range Weather Forecasts' ERA-Interim satellite reanalysis. Seventy-five out of eighty-six NWS cooperative stations depicted high counts of maximum low temperature records being set or broken since 1990. Twenty-four NWS hourly stations were used in conjunction with the...
Show moreWarm-season (1 June–31 August) near-surface moisture trends have been examined across Florida. Data was used from 86 National Weather Service cooperative stations, 24 NWS first-order stations, and the European Centre for Medium-Range Weather Forecasts' ERA-Interim satellite reanalysis. Seventy-five out of eighty-six NWS cooperative stations depicted high counts of maximum low temperature records being set or broken since 1990. Twenty-four NWS hourly stations were used in conjunction with the Pettitt test to calculate a change point of 1990 over a 40-year period (1973–2012). Using the Pettitt results, a significant amount of NWS first-order stations depicted a rise in both early morning temperatures and dew points (Td) since 1990. A rise in total column water vapor (TCWV) was detected through the ERA-Interim reanalysis, indicating a possible increase in mid-level moisture in addition to that near the surface. A reversal in 850 hPa wind patterns and a potential shift in the Azores High were present in the reanalysis as well. An increase in atmospheric moisture levels is present and may be driven by synoptic-scale changes in wind patterns due to a shift in the Azores High.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0528
Format: Thesis

Title: A High Resolution Atmospheric Chemistry Simulation of Hurricane Sandy (2012).
Creator: Freeman, Sean, Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: Hurricane Sandy (2012) had one of the greatest economic impacts of any hurricane in United States history. However, its broader scientific impacts, especially its impacts on the chemistry of the upper troposphere and lower stratosphere, have not been documented. This study uses the Weather Research and Forecasting with Chemistry model (WRF-Chem), run at a convective-permitting resolution, to examine the transport of pollutants inside Hurricane Sandy as it made landfall along the Eastern...
Show moreHurricane Sandy (2012) had one of the greatest economic impacts of any hurricane in United States history. However, its broader scientific impacts, especially its impacts on the chemistry of the upper troposphere and lower stratosphere, have not been documented. This study uses the Weather Research and Forecasting with Chemistry model (WRF-Chem), run at a convective-permitting resolution, to examine the transport of pollutants inside Hurricane Sandy as it made landfall along the Eastern Seaboard. Although several pollutants were examined, the concentrations of CO throughout the atmosphere and the transport of CO from sources along the coast in Hurricane Sandy's convective region were primary focus. A forward-trajectory analysis also was performed using the high-resolution WRF-Chem data as input to the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT). The results of this high-resolution chemical and meteorological simulation will be presented with a focus on transport to the upper troposphere and lower stratosphere. To our knowledge, such high-resolution chemical and meteorological simulations of tropical cyclones have not been reported in the previous literature.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0477
Format: Thesis

Title: An Analysis of the Extratropical Flow Response to Recurving Atlantic Tropical Cyclones.
Creator: Brannan, Allison, Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: There is a significant frequency of Atlantic tropical cyclones that complete extratropical transition and recurve in the mid-latitudes. Using a climatological approach, this study will analyze the extratropical flow response to recurving Atlantic tropical cyclones and compare the results to those from the Western North Pacific, as examined by Archambault et al. (2013). This investigation includes 54 recurving Atlantic tropical cyclones occurring between 2007 and 2013. The extratropical flow...
Show moreThere is a significant frequency of Atlantic tropical cyclones that complete extratropical transition and recurve in the mid-latitudes. Using a climatological approach, this study will analyze the extratropical flow response to recurving Atlantic tropical cyclones and compare the results to those from the Western North Pacific, as examined by Archambault et al. (2013). This investigation includes 54 recurving Atlantic tropical cyclones occurring between 2007 and 2013. The extratropical flow response will be quantified using potential vorticity. Characteristics of tropical cyclones, the extratropical jet stream, and the dynamical "phasing" of their interaction will be examined to determine the features that lead to significantly amplified extratropical flow. Results show the extratropical flow to be insensitive to the wind speed, latitude, and month of recurvature. However, there is an association between low mean sea level pressure and a larger amplification of flow. Finally, tropical cyclones recurving on the east side of the nearest trough are shown to have "favorable phasing," which yields amplification of the extratropical flow.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0538
Format: Thesis

Title: Investigating Relationships Between Rising Temperatures and Heavy Rainfall Events in the Southeastern U.S. Using Analog Methods.
Creator: Zuromski, Lauren, Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: This study examines how extreme precipitation influences temperatures, and how temperature extremes influence precipitation in the Southeastern U.S., seasonally, using observational data. For the precipitation influencing temperature approach, three precipitation regimes are created (wet, dry, and neutral) to observe possible shifts in the distributions of seasonal average daily maximum and minimum temperatures based on precipitation extremes. Similarly, for the temperature influencing...
Show moreThis study examines how extreme precipitation influences temperatures, and how temperature extremes influence precipitation in the Southeastern U.S., seasonally, using observational data. For the precipitation influencing temperature approach, three precipitation regimes are created (wet, dry, and neutral) to observe possible shifts in the distributions of seasonal average daily maximum and minimum temperatures based on precipitation extremes. Similarly, for the temperature influencing precipitation, three temperature regimes are created (warm, cool, and neutral), to observe how the frequency of rainfall events of 1.00" or more shifts in each temperature regime. For the precipitation influencing temperature approach, most notably, it is found that in summer, spring, and fall, in a wet precipitation regime, the maximum temperatures are typically warmer (cooler) than the average maximum temperatures in a neutral regime; the opposite pattern is observed for winter. It is also found that these temperature distributions do not shift in a uniform way across the Southeast, though several regional continuities exist. For the temperature influencing precipitation approach, it is found that spring, summer, and winter show the largest differences in the frequency of rainfall events of 1.00" or more between the cool and warm temperature regimes. This study also examines five case study stations in the Southeast to observe regional nuances in temperature and precipitation patterns.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0511
Format: Thesis

Title: IC to CG Lightning Relationships over the Tallahassee CWA.
Creator: Jackson, Karly M., Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: The formation of and the relationship between intra-cloud (IC) and cloud-to-ground (CG) lightning flashes have not been thoroughly studied. Understanding how these flash types interact in different types of thunderstorms can lead to a better understanding of lightning characteristics and how these characteristics can be applied to operational forecasting practices. Results of this study show that the IC:CG ratio varies greatly each day throughout the summer season over the County Warning Area...
Show moreThe formation of and the relationship between intra-cloud (IC) and cloud-to-ground (CG) lightning flashes have not been thoroughly studied. Understanding how these flash types interact in different types of thunderstorms can lead to a better understanding of lightning characteristics and how these characteristics can be applied to operational forecasting practices. Results of this study show that the IC:CG ratio varies greatly each day throughout the summer season over the County Warning Area (CWA) of the Tallahassee National Weather Service Forecast Office. The summer season is dominated by daily thunderstorms that form due to sea breeze fronts and their resulting outflow boundaries. Eleven case study storms reveal how IC and CG flash counts and rates in non-severe thunderstorms differ from those of severe storms such as those examined by Williams et al. (1999). Results of the present study reveal that the timing of CG lightning and the frequency of its strikes differ from those of severe storms. This is most likely due to severe storms producing stronger updrafts for longer periods of time than those of non-severe storms. The IC:CG ratios varied greatly among these case studies indicating that further studies must be done to determine a statistically significant understanding of how flash rates change and how the relationship between IC and CG flashes relate to the ratios they produce.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0552
Format: Thesis

Title: Remotely Sensed Validation of Numerical Weather Prediction Estimates of Wind Speed Near Tropical Cyclones.
Creator: Dacey, Connor, Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: This study examined the tendencies of the European Center for Medium-Range Weather Forecasting Ensemble Prediction System (ECMWF-EPS) control forecast of wind speeds near two rapidly intensifying tropical cyclones (TCs) in the Indian Ocean. The ECMWF-EPS control forecasts were compared with the Advanced Scatterometer (ASCAT) wind speed measurements, which were considered comparison and "truth" data for this study. In total, 6 days of model forecast and ASCAT data were collected and analyzed...
Show moreThis study examined the tendencies of the European Center for Medium-Range Weather Forecasting Ensemble Prediction System (ECMWF-EPS) control forecast of wind speeds near two rapidly intensifying tropical cyclones (TCs) in the Indian Ocean. The ECMWF-EPS control forecasts were compared with the Advanced Scatterometer (ASCAT) wind speed measurements, which were considered comparison and "truth" data for this study. In total, 6 days of model forecast and ASCAT data were collected and analyzed for severe tropical cyclones Phet and Giri. Differences in the magnitudes of the wind speeds near the TCs were calculated. From these, areas can be seen in which the ECMWF-EPS control over-forecasted and under-forecasted the wind speeds. These results also help explain how the model tendencies changed throughout the lifespan of the TCs. Overall, wind speed errors were greatly associated with errors in storm location, storm shape, and storm size. No exact conclusion about the tendencies of the ECMWF-EPS control forecasts could be made due to a lack of patterns or clear biases associated with the wind speed difference results. A more in-depth study must be completed to further comment on specific tendencies of the model. Nevertheless, this study could begin the investigation into how to improve wind speed forecasts for TCs in the Indian Ocean in an effort to better save life and property in the future.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0548
Format: Thesis

Title: Quantification of Stokes Drift as a Mechanism for Surface Oil Advection in the Gulf of Mexico during the Deepwater Horizon Oil Spill.
Creator: Clark, Matthew, Bourassa, Mark Allan, Chassignet, Eric P., Hart, Robert E. (Robert Edward), Florida State University, College of Arts and Sciences, Department of Earth, Ocean,...
Show moreClark, Matthew, Bourassa, Mark Allan, Chassignet, Eric P., Hart, Robert E. (Robert Edward), Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: Wave-driven transport, also known as Stokes drift, is the motion of a particle due to the orbital motion induced by a passing wave. This orbital motion does not form closed loops, leading to a net displacement over a single wave period. Stokes drift has previously been qualitatively shown to be a factor in ocean surface particle transport, with most studies focused exclusively in near-shore regions. However, Stokes drift has never been quantified beyond theoretical studies and case studies...
Show moreWave-driven transport, also known as Stokes drift, is the motion of a particle due to the orbital motion induced by a passing wave. This orbital motion does not form closed loops, leading to a net displacement over a single wave period. Stokes drift has previously been qualitatively shown to be a factor in ocean surface particle transport, with most studies focused exclusively in near-shore regions. However, Stokes drift has never been quantified beyond theoretical studies and case studies limited to small regions. Here, Stokes drift is calculated directly from Wavewatch III model data in the Gulf of Mexico for April-July 2010. Its magnitudes are compared between deep and shelf water areas, and against the magnitudes of surface currents and parameterized wind drift. These comparisons are also made specifically for the time period surrounding the passage of Hurricane Alex through the southwestern Gulf of Mexico. While there is not a major difference between the absolute magnitudes of Stokes drift in shelf vs. deep water areas or when compared to wind drift, Stokes drift is larger in shelf water areas relative to surface currents than in deep water. During Hurricane Alex, Stokes drift magnitudes were much larger in the immediate area of the storm, while in the oil spill area there was little change until after the storm was out of the Gulf, at which time swell had propagated into the region, increasing Stokes drift magnitudes.
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Date Issued: 2015
Identifier: FSU_migr_etd-9576
Format: Thesis

Title: Investigating the Potentially Untapped Predictability of Tropical Cyclone Genesis in Operational Global Models.
Creator: Halperin, Daniel J., Fuelberg, Henry E., Hart, Robert E. (Robert Edward), Harper, Kristine, Chagnon, Jeffrey M., Liu, Guosheng, Florida State University, College of Arts and...
Show moreHalperin, Daniel J., Fuelberg, Henry E., Hart, Robert E. (Robert Edward), Harper, Kristine, Chagnon, Jeffrey M., Liu, Guosheng, Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: There is an operational need for accurate tropical cyclone (TC) genesis forecasts. Global numerical models are an important genesis guidance tool, but each model has biases. Further, the interpretation of when genesis occurs in a model forecast field can be subjective. Thus, this study seeks to create an automated, objective, statistical-dynamical TC genesis guidance tool for the North Atlantic and eastern North Pacific basins based on output from the CMC, GFS, and UKMET global models....
Show moreThere is an operational need for accurate tropical cyclone (TC) genesis forecasts. Global numerical models are an important genesis guidance tool, but each model has biases. Further, the interpretation of when genesis occurs in a model forecast field can be subjective. Thus, this study seeks to create an automated, objective, statistical-dynamical TC genesis guidance tool for the North Atlantic and eastern North Pacific basins based on output from the CMC, GFS, and UKMET global models. Another goal is to determine how well important genesis processes in global models agree with those theoretically proposed. This research also attempts to identify the characteristics of successful and failed genesis forecasts. First, historical global model forecasts of TC genesis over the past decade are verified. Using this genesis forecast archive, univariable logistic regression equations are created to reveal the statistical relationships between relevant variables and genesis probability. These statistical relationships are compared to theoretical relationships between atmospheric variables and TC genesis. Results show several expected and counterintuitive statistical relationships, with some disagreement among the models. Multiple logistic regression equations then are developed to provide probabilistic genesis forecasts. Separate equations are developed for each global model, basin, and forecast window. Additionally, a consensus regression equation is developed. These equations are tested operationally during the 2014 hurricane season. Verification of the independent data indicates generally well-calibrated guidance. Homogeneous comparisons of the consensus regression equation and National Hurricane Center Tropical Weather Outlook genesis probabilities are presented. Case studies and composite analyses are conducted to gain further insight. Case studies from the following categories are selected: (1) African Easterly Wave genesis over the Main Development Region; (2) genesis from stalled frontal boundaries; (3) genesis via tropical transition; and (4) genesis over the Gulf of Mexico. Hit, miss, and false alarm events are compared. Storm centered composite analyses also are constructed to examine differences in the environments between hit and false alarm forecasts. Separate composites are made for the eastern Main Development Region (where the GFS false alarm rate is greatest) and the remainder of the North Atlantic basin. Statistically significant differences between hit and false alarm cases are found for all variables analyzed with various areal extents. Results from the case studies and composite analyses will help guide new predictors to test for inclusion into the multiple logistic regression equations. Additionally, the case study of Sean (2011) suggests that changes to the TC identification algorithm are needed to better detect subtropical to tropical transition. Real-time guidance products based on the logistic regression equations are being evaluated by hurricane specialists at the National Hurricane Center. It is possible that the products will be selected for operational implementation pending further testing and evaluation during 2015.
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Date Issued: 2015
Identifier: FSU_migr_etd-9607
Format: Thesis

Title: Analysis and Prediction of Integrated Kinetic Energy in Atlantic Tropical Cyclones.
Creator: Kozar, Michael E., Misra, Vasubandhu, Ye, Ming, Hart, Robert E. (Robert Edward), Sura, Philip, Clarke, Allan J., Powell, Mark Dillon, Florida State University, College of Arts...
Show moreKozar, Michael E., Misra, Vasubandhu, Ye, Ming, Hart, Robert E. (Robert Edward), Sura, Philip, Clarke, Allan J., Powell, Mark Dillon, Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: Integrated kinetic energy (IKE) is a recently developed metric that approximates the destructive potential of a tropical cyclone by assessing the size and strength of its wind field. Despite the potential usefulness of the IKE metric, there are few, if any, operational tools that are specifically designed to forecast IKE in real-time. Therefore, IKE and tropical cyclone structure are analyzed within historical Atlantic tropical cyclones from the past two decades in order to develop an...
Show moreIntegrated kinetic energy (IKE) is a recently developed metric that approximates the destructive potential of a tropical cyclone by assessing the size and strength of its wind field. Despite the potential usefulness of the IKE metric, there are few, if any, operational tools that are specifically designed to forecast IKE in real-time. Therefore, IKE and tropical cyclone structure are analyzed within historical Atlantic tropical cyclones from the past two decades in order to develop an understanding of the environmental and internal storm-driven processes that govern IKE variability. This analysis concurs with past research that IKE growth and decay is influenced by both traditional tropical cyclone development mechanisms and by other features such as extratropical transition and trough interactions. Using this framework, a series of statistical prediction tools are created in an effort to project IKE in Atlantic tropical cyclones from a series of relevant normalized input parameters. The resulting IKE prediction schemes are titled the "Statistical Prediction of Integrated Kinetic Energy (SPIKE)". The first version of SPIKE utilizes simple linear regression to project historical IKE quantities in a perfect prognostic mode for all storms between 1990 and 2011. This primitive model acts as a proof of concept, revealing that IKE can be skillfully forecasted relative to persistence out to 72 hours by even the simplest of statistical models if given accurate estimates of various metrics measured throughout the storm and its environment. The proof-of-concept version of SPIKE is improved upon in its second version, SPIKE2, by incorporating a more sophisticated system of adaptive statistical models. A system of artificial neural networks replaces the linear regression model to better capture the nonlinear relationships in the TC-environment system. In a perfect prognostic approach with analyzed input parameters, the neural networks outperform the linear models in nearly every measurable way. The system of neural networks is also more versatile, as it is capable of producing both deterministic and probabilistic tools. Overall, the results from these perfect prognostic exercises suggest that SPIKE2 has a high potential skill level relative to persistence and several other benchmarks. Finally, in an effort to assess its real-time performance, the SPIKE2 forecasting system is run in a mock-operational hindcast mode for the 1990 to 2011 North Atlantic hurricane seasons. Hindcasts of IKE are produced in this manner by running the neural networks with hindcasted input parameters from NOAA's second generation Global Ensemble Forecast System reforecast dataset. Ultimately, the results of the hindcast exercises indicate that the neural network system is capable of skillfully forecasting IKE in an operational setting at a level significantly higher than climatology and persistence. Ultimately, forecasts of IKE from these neural networks could potentially be an asset for operational meteorologists that would complement existing forecast tools in an effort to better assess the damage potential of landfalling tropical cyclones, particularly with regards to storm surge damage.
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Date Issued: 2015
Identifier: FSU_migr_etd-9376
Format: Thesis

Title: ENSO Variability in a Changing Climate.
Creator: Feng, Jiaxin, Wu, Zhaohua, Ye, Ming, Clarke, Allan J., Liu, Guosheng, Sura, Philip, Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and...
Show moreFeng, Jiaxin, Wu, Zhaohua, Ye, Ming, Clarke, Allan J., Liu, Guosheng, Sura, Philip, Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: Since 1980, a new type of ENSO, i.e., central Pacific (CP) ENSO, where sea surface temperature anomalies (SSTAs) are mainly located in the equatorial central Pacific, has been frequently observed. Several studies have documented and predicted a higher occurrence ratio of CP ENSO to eastern Pacific (EP) ENSO, where SSTAs mainly occur in the equatorial eastern Pacific, in a warming climate. Most studies centered on the difference between CP and EP ENSO have used traditional analysis methods,...
Show moreSince 1980, a new type of ENSO, i.e., central Pacific (CP) ENSO, where sea surface temperature anomalies (SSTAs) are mainly located in the equatorial central Pacific, has been frequently observed. Several studies have documented and predicted a higher occurrence ratio of CP ENSO to eastern Pacific (EP) ENSO, where SSTAs mainly occur in the equatorial eastern Pacific, in a warming climate. Most studies centered on the difference between CP and EP ENSO have used traditional analysis methods, such as PCA/EOF analysis and regression, to define or differentiate the aforementioned two types of ENSO. However, the results obtained using these methods can only reveal accumulated spatial information which contributed most to the variance of the data, which is the usually the spatial information during the mature (peak) stage of ENSO; this spatial information is a static pattern and is not able to reveal sequential development of ENSO, which should be crucial for physical interpretations. In addition, although this spatial information in generally true for the entire temporal span, it is not necessarily true for any subperiods and thus not able to reveal any potential characteristic change of ENSO over time. In this study, an alternative Niño 3.4 index is defined to reflect only the interannual variability of equatorial Pacific SSTAs. Using this alternative index, we identify 28 El Niño events and 31 La Niña events. Then, we employ a newly developed analysis method, i.e., fast multidimensional ensemble empirical mode decomposition (FMEEMD), to extract the interannual spatiotemporal evolution of SSTAs to examine the developments of the identified ENSO events. All events are classified into four types of ENSO based on the interannual evolutions of SSTAs early in the development stage: (1) EP ENSO, (2) eastern-central Pacific (ECP) ENSO, (3) western-central Pacific (WCP) ENSO, and (4) mixed (MIX) ENSO. We apply the same method to analyze surface horizontal wind and thermocline depth data, and phase composite analyses on SSTAs, surface wind anomalies and thermocline depth anomalies are performed for each type of El Niño events. The results show four distinctive evolution patterns; it is found that La Niña events also have similar variation in the evolution patterns. The lower-frequency variability and change (decadal and longer time scales, including secular trend trend) in SSTAs, surface wind anomalies and thermocline depth anomalies are also examined. The secular trends show weak surface cooling over the central Pacific between 140°W and 160°W near the Equator, consistent with the anomalous wind divergence and thermocline shoaling in the same region. In response to decadal and lower-frequency oscillatory wind forcing, the background state of the thermocline is modified in a way that when western-central Pacific is dominated by shoaling (deepening), the eastern Pacific is dominated by deepening (shoaling). The combined effect of the secular trends and lower-frequency oscillatory variability is that for some decade(s), the thermocline depth is anomalously shallower (deeper) in the western-central Pacific region, while the thermocline depth is anomalously deeper (shallower) in the east. We suggest that this "seesaw" pattern in the depth anomalies across the Equator determines the evolving patterns of ENSO by hinder/facilitating the communication between ocean surface and subsurface, and thus modifying the effect of wave-associated thermocline displacements on SST change over the western-central Pacific. Additionally, for WCP and some of the MIX ENSO events, a potential SSTA precursor from Baja California/northeastern Pacific might be instrumental to the subsequent development, possibly by inducing zonal wind anomalies in the western Pacific.
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Date Issued: 2015
Identifier: FSU_migr_etd-9330
Format: Thesis

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

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

Title: The Increasing Intensity and Frequency of ENSO and its Impacts to the Southeast U.S.
Creator: McNaught, Carlysle, Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: The El Niño Southern Oscillation (ENSO) is an important natural climate variation that affects large portions of the world. The changing magnitude and frequency of ENSO reveals that it is getting stronger as measured by the maximum anomaly in sea surface temperature (SST). Principal component analysis of the ENSO is conducted to estimate the spectrum of the SST of the time series. The intensity of the ENSO events during the period 1970—2010 is statistically significantly higher when compared...
Show moreThe El Niño Southern Oscillation (ENSO) is an important natural climate variation that affects large portions of the world. The changing magnitude and frequency of ENSO reveals that it is getting stronger as measured by the maximum anomaly in sea surface temperature (SST). Principal component analysis of the ENSO is conducted to estimate the spectrum of the SST of the time series. The intensity of the ENSO events during the period 1970—2010 is statistically significantly higher when compared to the period 1930—1970, with a broad spectral peak centered around 4 years. When we compare the SST spectrum for the period 1930—1970 with the spectrum for 1970—2010, we find the latter period to be much stronger in power. The resultant impact of more powerful and frequent ENSO events on the Southeast United States is examined through a spatial and temporal statistical analysis of precipitation and temperatures between the two time periods. Our analysis reveals statistically significant changes in precipitation during El Niño where the rainfall is much more widespread across the Southeast during the 1970—2010 period than the 1930—1970 period. The La Niña rainfall deficit is mainly confined to Florida in the latter period than the former. Finally, the temperature distribution, through an analysis of the first four statistical moments, showed conventional responses to the changes in ENSO precipitation such as an anomalous decrease in maximum temperatures during El Niño and an overall anomalous increase in temperatures during La Niña.
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Date Issued: 2014
Identifier: FSU_migr_uhm-0356
Format: Thesis

Title: Hurricane Sandy and New Jersey: The Nature of a Natural Disaster.
Creator: Blaskiewicz, Claire S., Department of Earth, Ocean and Atmospheric Sciences
Abstract/Description: While natural disasters can often be catalysts for change, understanding where to begin changing can be discovered by looking at the science and history of the affected area. Hurricane Sandy's unprecedented landfall in October 2012 began this progression for the state of New Jersey. This study examines the processes affecting the ocean and beaches of New Jersey, looks at the effects of Hurricane Sandy on the state and discusses the changing standards that have been and continue to be enacted...
Show moreWhile natural disasters can often be catalysts for change, understanding where to begin changing can be discovered by looking at the science and history of the affected area. Hurricane Sandy's unprecedented landfall in October 2012 began this progression for the state of New Jersey. This study examines the processes affecting the ocean and beaches of New Jersey, looks at the effects of Hurricane Sandy on the state and discusses the changing standards that have been and continue to be enacted since storm recovery began. Specifically highlighted are the engineering practices of flood mitigation, the effects of the storm on the state's economy and the new policies and standards that have come about in the aftermath.
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Date Issued: 2014
Identifier: FSU_migr_uhm-0564
Format: Thesis

Title: The Influence of Mesoscale Sea Surface Temperature Gradients on Tropical Cyclones.
Creator: Glazer, Russell Henderson, Bourassa, Mark A., Hart, Robert Edward, Powell, Mark Dillon, Misra, Vasubandhu, Florida State University, College of Arts and Sciences, Department of...
Show moreGlazer, Russell Henderson, Bourassa, Mark A., Hart, Robert Edward, Powell, Mark Dillon, Misra, Vasubandhu, Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: The effects of mesoscale (50-1000km) sea surface temperature (SST) variability on tropical cyclones (TCs) are investigated with model simulations of an idealized TC as well as simulations of Hurricane Igor (2010) using the Weather Research and Forecasting (WRF) model. Mesoscale SST gradients significantly modify the surface wind speed and direction leading to areas of enhanced divergence/convergence and curl along the gradient. This paper explores the effects that these interactions between...
Show moreThe effects of mesoscale (50-1000km) sea surface temperature (SST) variability on tropical cyclones (TCs) are investigated with model simulations of an idealized TC as well as simulations of Hurricane Igor (2010) using the Weather Research and Forecasting (WRF) model. Mesoscale SST gradients significantly modify the surface wind speed and direction leading to areas of enhanced divergence/convergence and curl along the gradient. This paper explores the effects that these interactions between mesoscale SST gradients and the atmosphere have on TCs. In these idealized simulations it is shown that an SST gradient of similar scale to the idealized TC vortex produces asymmetry in the eyewall convection and leads to vertical misalignment of the vortex. Simulations of Igor are conducted with three different SST setups: a run with an unaltered SST field, a run with increased SST gradients, and a run with decreased SST gradients. Igor's intensity and structure is found to be sensitive to the three different SST setups but the specific mechanism could not be identified. It is found that the magnitude of moisture advection increases with increasing SST gradient magnitude on the warm side of a gradient.
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Date Issued: 2014
Identifier: FSU_migr_etd-9177
Format: Thesis

Title: Global Warming and Tropical Cyclone Climate in the Western North Pacific.
Creator: Kang, Nam-Young, Elsner, James B., Hart, Robert Edward, Speer, Kevin G. (Kevin George), Bourassa, Mark A., Florida State University, College of Arts and Sciences, Program in...
Show moreKang, Nam-Young, Elsner, James B., Hart, Robert Edward, Speer, Kevin G. (Kevin George), Bourassa, Mark A., Florida State University, College of Arts and Sciences, Program in Geophysical Fluid Dynamics
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Abstract/Description: Violent tropical cyclones (TCs) continue to inflict serious impacts on national economies and welfare, but how they are responding to global warming has not been fully clarified. Here I construct an empirical framework that shows the observations supporting a strong link between rising global ocean warmth and increasing trade-off between TC intensity and frequency in the western North Pacific. Thermodynamic structure of the tropical western North Pacific with high global ocean warmth is...
Show moreViolent tropical cyclones (TCs) continue to inflict serious impacts on national economies and welfare, but how they are responding to global warming has not been fully clarified. Here I construct an empirical framework that shows the observations supporting a strong link between rising global ocean warmth and increasing trade-off between TC intensity and frequency in the western North Pacific. Thermodynamic structure of the tropical western North Pacific with high global ocean warmth is characterized by convectively more unstable lower troposphere with greater heat and moisture, but this instability is simultaneously accompanied by anomalous high pressure in the middle and upper troposphere over the same region. Increasing trade-off level between TC intensity and frequency in a warmer year proves that this environment further inhibits the TC occurrences over the region, but TCs that form tend to discharge stored energy to upper troposphere with stronger intensities. By increasing the intensity threshold at higher levels we confirmed that the TC climate connection with global ocean warmth occurs throughout the strongest portion of TCs, and the environmental connection of the TC climate is more conspicuous in the extreme portion of TCs. Intensities at the strongest 10~% of the western North Pacific TCs are comparable to super typhoons on average, the increasing trade-off magnitude clearly suggests that super typhoons in a warmer year gets stronger. Conclusively, the negative collinear feature of the thermodynamics influences the portion of TCs at the highest intensities, and super typhoons are likely to become stronger at the expense of overall TC frequencies in a warmer world. The consequence of this finding is that record-breaking TC intensities occur at the expense of overall TC frequencies under global warming. TC activity is understood as a variation which is independent of global warming, and could be assumed to be an internal variability having no trend. Frequency variation and super typhoon intensity variation are regarded as the addition of global warming influence on TC activity variation. The structure depicts how a previous intensity record is overtaken and frequency falls continuously in the global warming environment in a linear perspective. A peak TC activity year when global ocean warmth is the highest ever is likely to experience a record-breaking intensity. In the same way, the least number of annual TCs may appear when a lull of TC activity occurs in the warmest year.
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Date Issued: 2014
Identifier: FSU_migr_etd-9196
Format: Thesis

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

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: 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: 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: 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: The Influence of Atmospheric Cold Air Outbreaks on the Upper Ocean Thermal Variability of the Florida Straits.
Creator: Rudzin, Johna, Earth, Ocean & Atmospheric Science
Abstract/Description: The purpose of this study is to investigate the impacts of cold air outbreaks (CAOs) on the sea surface temperature (SST) in the Florida Straits (FS) during different configurations (mature or immature) of the Loop Current (LC). A satellite-derived SST data set is used to calculate the difference in SST anomalies between the FS and the Yucatan Channel (YC). The SST anomaly time series is analyzed during the winter season for times of mature and immature LC configurations determined from a...
Show moreThe purpose of this study is to investigate the impacts of cold air outbreaks (CAOs) on the sea surface temperature (SST) in the Florida Straits (FS) during different configurations (mature or immature) of the Loop Current (LC). A satellite-derived SST data set is used to calculate the difference in SST anomalies between the FS and the Yucatan Channel (YC). The SST anomaly time series is analyzed during the winter season for times of mature and immature LC configurations determined from a satellite altimetry-derived time series of LC position. This analysis shows a greater likelihood of anomalous cooling of SSTs in the FS compared to the SSTs in the YC during times of an extended, or mature, LC. This result leads to the hypothesis that surface water is subject to greater cooling during a mature LC (due to the greater residence time of the water under cold air masses) than an immature LC, and this cooler water is advected into the FS. This hypothesis is investigated by computing an approximate heat budget for the Yucatan-Loop-Florida Current (YLFC) under identical atmospheric forcing using twin ocean model simulations with mature and immature LC configurations.
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Date Issued: 2012
Identifier: FSU_migr_uhm-0056
Format: Thesis

Title: Multi-Decadal Variations of Durations of Extreme Temperatures in the Southeastern United States.
Creator: Worsnop, Rochelle, Earth, Ocean & Atmospheric Science
Abstract/Description: The number of extreme temperature occurrences and their durations in the southeast United States varies during three periods: the Warm Regime subset (WRs), the Cold Regime subset (CRs), and the Modern Record (MR). Multidecadal variations in the regional patterns of the counts and durations of summer-day and winter-day extremes reveal that during the MR, the extreme temperature counts and durations in Florida are more consistent with a WRs setup whereas these parameters for the inland states ...
Show moreThe number of extreme temperature occurrences and their durations in the southeast United States varies during three periods: the Warm Regime subset (WRs), the Cold Regime subset (CRs), and the Modern Record (MR). Multidecadal variations in the regional patterns of the counts and durations of summer-day and winter-day extremes reveal that during the MR, the extreme temperature counts and durations in Florida are more consistent with a WRs setup whereas these parameters for the inland states (Alabama, Georgia, North Carolina, and South Carolina) are more consistent with a CRs setup. We also found that during the CRs (WRs), the majority of stations show a statistically significant increase in the likelihood of exactly one winter-day (summer-day) extreme occurrence. During the MR, both inland and coastal stations show a statistically significant increase in the likelihood of exactly one winter-day occurrence. This increased likelihood is not seen during the MR for a summer-day extreme occurrence. Patterns in the behavior of summer-day and winter-day extremes during the CRs and WRs may provide insight about how extreme temperatures will behave in future periods, if the period is forecasted to have similar setups to that of the CRs or WRs. Insight about the duration and counts of extreme temperatures is useful to the agricultural community, power industries, and health officials.
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Date Issued: 2012
Identifier: FSU_migr_uhm-0050
Format: Thesis

Title: Characteristics of WTLN-Derived Lightning.
Creator: Saunders, Matthew, Earth, Ocean & Atmospheric Science
Abstract/Description: Many studies have used cloud-to-ground (CG), intracloud (IC), and total (CG + IC) lightning to investigate relationships between lightning and severe weather. Although the National Lightning Detection Network (NLDN) is the most common system used to detect lightning, it is limited to reporting only CG lightning over the continental United States. The WeatherBug Total Lightning Network (WTLN) is a global data set recently established by Earth Networks, Inc. that reports both CG and IC...
Show moreMany studies have used cloud-to-ground (CG), intracloud (IC), and total (CG + IC) lightning to investigate relationships between lightning and severe weather. Although the National Lightning Detection Network (NLDN) is the most common system used to detect lightning, it is limited to reporting only CG lightning over the continental United States. The WeatherBug Total Lightning Network (WTLN) is a global data set recently established by Earth Networks, Inc. that reports both CG and IC lightning. WTLN has the potential to offer superior lightning data, although little research has compared WTLN information to other data sets like the NLDN. Using WTLN and NLDN data, distributions of stroke counts by polarity and peak current were plotted during a16-month study period near Cape Canaveral, FL. The WTLN data set showed an over detection of weak peak current strokes and under detection of strong peak current strokes. The WTLN data also exhibited higher overall stroke counts compared to NLDN. A case study of the Tuscaloosa-Birmingham tornado showed an opposite relation between WTLN and NLDN stroke counts. Compared to NLDN, the WTLN continually undercounted strokes during the lifecycle of the storm. While the number of counts was dissimilar, the two data sets correlated strongly (0.79) during the storm period. When the lightning was divided by polarity, WTLN showed a much greater detection of positive CG lightning than NLDN.
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Date Issued: 2012
Identifier: FSU_migr_uhm-0055
Format: Thesis

Title: Separation and Characterization of Copper Binding Ligands in Dissolved Organic Matter in Lake Bradford.
Creator: Prugue, Rodrigo, Earth, Ocean & Atmospheric Science
Abstract/Description: Trace metals are important compounds in aquatic environments. In low concentrations, they can be very beneficial to aquatic life. However, they can be toxic if present in moderate to high concentrations. A growing interest has occurred involving ligands. Trace metals like copper are most commonly found complexed with ligands in fresh and marine waters. Many organisms also produce compounds to help mitigate increases in dissolved copper and prevent toxic environments. However, very little is...
Show moreTrace metals are important compounds in aquatic environments. In low concentrations, they can be very beneficial to aquatic life. However, they can be toxic if present in moderate to high concentrations. A growing interest has occurred involving ligands. Trace metals like copper are most commonly found complexed with ligands in fresh and marine waters. Many organisms also produce compounds to help mitigate increases in dissolved copper and prevent toxic environments. However, very little is known on how these ligands behave and what causes them to complex with trace metals. This project aims to separate and characterize copper binding ligands from a local lake in Tallahassee, FL. The motivation is to improve understanding of this complex process and mitigate future environmental issues dealing with elevated issues of metals in aquatic environments. UV/Vis spectrometry data did not yield any conclusive results since the peaks seen were very similar to what copper and the chelating agent used, EDTA, looked like. However, the data produced by the electrospray ionization mass spectrometer does indicate the presence of specific compounds which were affected by the pH of the solution. Although the data did not yield any characteristic data, we concluded that the IMAC process is capable of fractionating copper binding ligands.
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Date Issued: 2012
Identifier: FSU_migr_uhm-0064
Format: Thesis

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: 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: 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: 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: 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

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