How much warmer is the ocean surface than the atmosphere directly above it? Part 1 of the present study offers a means to quantify this temperature difference using a nonlinear one-dimensional global energy balance coupled ocean–atmosphere model ("Aqua Planet"). The significance of our model, which is of intermediate complexity, is its ability to obtain an analytical solution for the global average temperatures. Preliminary results show that, for the present climate, global mean ocean temperature is 291.1 K whereas surface atmospheric temperature is 287.4 K. Thus, the surface ocean is 3.7 K warmer than the atmosphere above it. Temporal perturbation of the global mean solution obtained for "Aqua Planet" showed a stable system. Oscillation amplitude of the atmospheric temperature anomaly is greater in magnitude to those found in the ocean. There is a phase shift (a lag in the ocean), which is caused by oceanic thermal inertia. Climate feedbacks due to selected climate parameters such as incoming radiation, cloud cover, and CO2 are discussed. Warming obtained with our model compares with Intergovernmental Panel on Climate Change's (IPCC) estimations. Application of our model to local regions illuminates the importance of evaporative cooling in determining derived air-sea temperature offsets, where an increase in the latter increases the systems overall sensitivity to evaporative cooling. In part 2, we wish to answer the fairly complicated question of whether global warming and an increased freshwater flux cause Northern Hemispheric warming or cooling. Starting from the assumption of the ocean as the primary source of variability in the Northern hemispheric ocean–atmosphere coupled system, we employed a simple non–linear one–dimensional coupled ocean–atmosphere model similar to the "Aqua Planet" model but with additional advective heat transports. The simplicity of this model allows us to analytically predict the evolution of many dynamical variables of interest such as, the strength of the Atlantic Meridional overturning circulation (AMOC), temperatures of the ocean and atmosphere, mass transports, salinity, and ocean–atmosphere heat fluxes. Model results show that a reduced AMOC transport due to an increased freshwater flux causes cooling in both the atmosphere and ocean in the North Atlantic (NA) deep–water formation region. Cooling in both the ocean and atmosphere can cause a reduction of the ocean–atmosphere temperature difference, which in turn reduces heat fluxes in both the ocean and atmosphere. For present day climate parameters, the calculated critical freshwater flux needed to arrest AMOC is 0.14 Sv. Assuming a constant atmospheric zonal flow, there is both minimal reduction in the AMOC strength, as well as minimal warming of the ocean and atmosphere. This model provides a conceptual framework for a dynamically sound response of the ocean and atmosphere to AMOC variability as a function of increased freshwater flux. The results are qualitatively consistent with numerous realistic coupled numerical models of varying complexity. / A Dissertation submitted to the Geophysical Fluid Dynamics Institute in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2015. / November 2, 2015. / air-sea temperature difference, AMOC, freshwater flux, local cooling, ocean-atmosphere interaction, simple models / Includes bibliographical references. / Doron Nof, Professor Directing Dissertation; Christopher Tam, University Representative; Mark Bourassa, Committee Member; Allan Clarke, Committee Member; Philip Sura, Committee Member; Brian Ewald, Committee Member.

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 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. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2015. / November 10, 2015. / convective dynamics, deep convection, large-eddy simulation, WRF / Includes bibliographical references. / Henry E. Fuelberg, Professor Directing Dissertation; Ingo Wiedenhoever, University Representative; Robert E. Hart, Committee Member; Mark A. Bourassa, Committee Member; Vasu Misra, Committee Member; Francis J. Turk, Committee Member.

The Paleozoic growth of the eastern margin of the North American continent is exemplified by the amalgamation of a series of terranes due to the closure of intervening ocean(s) and the obduction of fragments of oceanic and continental crust. The Appalachian orogen has traditionally been described as a culmination of three distinct events including the Taconic, Acadian, and Alleghanian orogenies. While evidence of the aforementioned discrete events has been well documented in the Appalachians in general, substantiation of the effects and timing of each orogeny appears to be more ambiguous regionally, likely requiring differing tectonic models along strike of the orogenic belt. The response of Laurentia to orogenesis is important in determining the timing and extent of Paleozoic accretionary events as well as characterizing the accreted terranes themselves. Tectonic models of classically studied mountain belts including the Alps, Himalayas, and Appalachians were constructed relying heavily on identifying collisional structures formed during closure of an intervening ocean(s). The modern Pacific margin represents an alternative to collisional models termed accretionary orogenesis. Accretionary orogenesis is also variable in that there may be an advancing subduction boundary or a retreating subduction boundary (extensional accretionary orogen). This study examines the role of crustal growth in an accretionary margin along the southeastern margin of Laurentia during a time of extensive (orogen-wide) arc accretion and closure of an intervening ocean commonly associated with the Ordovician-aged Taconic orogeny. Structural, stratigraphic, geochemical and isotopic evidence suggest that the southeastern margin of Laurentia (Alabama promontory) remained open to an ocean (as an accretionary orogen) until at least the Acadian and possibly as late as the Alleghanian orogeny. The structural architecture of the terrane-bounding fault (Allatoona and Hollins-Line faults) systems and adjacent terranes and petrogenesis of arc-related volcanics and plutonic bodies provides insight into the early Paleozoic evolution of the southeastern margin of Laurentia. / A Dissertation submitted to the Department of Geological Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2006. / July 25, 2006. / Pumpkinvine Creek Formation, Granitoids, New Georgia Group, Canton Formation, Villa Rica Gneiss, Sand Hill Gneiss, Austell Gneiss, Zana-Kowaliga Gneiss, Mulberry Rock Gneiss, Elkahatchee Quartz Diorite, Hollins-Line Fault, Allatoona Fault, Hillabee Greenstone, Appalachians, Terrane Accretion, Georgia, Alabama, Blue Ridge, Paleozoic / Includes bibliographical references. / James F. Tull, Professor Directing Dissertation; Philip Froelich, Outside Committee Member; A. Leroy Odom, Committee Member; Stephen A. Kish, Committee Member.

The use of chemical tracers to understand ecosystem interactions in the marine environment has gained increasing popularity over the past three decades. Carbon isotope abundances in organic matter sources in the marine system vary significantly making them a useful tracer for discriminating among such sources. Once taken up by primary producers, carbon isotope abundances are conservative throughout the food web. This allows us to measure carbon isotope abundances in secondary (and above) consumers and infer organic matter source utilization in the system. Nitrogen isotope abundances, unlike carbon, are not conservative throughout the food web. However, they do fractionate predictably providing a tool by which to measure trophic level of consumer species. Sulfur isotopes, like carbon, differ among sources and are also conservative within the food web providing an additional tracer with which to estimate source contributions. However, concerns about the "dirtiness" of sulfur for analysis purposes put sulfur on the back burner as an ecosystem tracer. With recent improvements in technology and the need for multiple tracers in multi-source systems, sulfur isotope abundance measurements have experienced a resurgence. In this manuscript we use sulfur isotope abundances as a second tracer (with carbon isotope abundances) to estimate organic matter source utilization by consumers in a variety of habitats along the Florida Big Bend coastline. We begin our isotopic analysis of consumers in a Northwest Gulf of Mexico, freshwater dominated estuarine system, Apalachicola Bay, Florida (USA). In Chapter II we evaluate isotopic variation with body size to determine the smallest trophic unit in our system. In Chapter III we develop a concentration-corrected, dual-isotope, multi-source evaluation of organic matter utilization incorporating sulfur as a secondary tracer. We then go on to apply the results of this model to determine trophic level of consumers in Apalachicola Bay based on nitrogen isotope abundance data. In Chapter IV we demonstrate how isotopic variation of sources within a system can confound our interpretations of trophic structure using these methods. We further demonstrate that, in addition to isotopic variation, source inputs and availability may also vary within a given system. This makes comparison among sites more difficult and highlights the need to evaluate isotopic variation in individual systems prior to making comparisons or widespread generalizations about interactions. In Chapter V we apply these methods to a coastal seagrass community. We evaluate isotopic abundances in sources in consumers from the site. Then we apply the mixing model we develop in Chapter II to determine organic matter source utilization by consumers. Finally, we evaluate trophic level of individual consumers and trophic structure of the system based on nitrogen isotopic abundances. We demonstrate that source isotopic abundances differ from those same sources in the freshwater estuarine habitats. We also show that, while benthic organic matter was an important source in Apalachicola Bay, epiphytes provide the major organic matter source supporting consumers in the seagrass habitat. We use source utilization information and trophic level to assign consumers to trophic guilds in this system. The variety of organic matter source utilization is thought to contribute to the high levels of productivity found in this region. In addition to natural tracers, such as isotope abundances, we have also used organic pollutants as tracers of habitat utilization in the Florida Big Bend region. Organic contaminants found in coastal waters include compounds such as DDTs, PCBs, and chlordanes. Although no longer produced in the U.S., their historically wide-spread use and resistance to degradation contributes to their persistence in marine biota. We present data on chemical concentrations and congener profiles in bottlenose dolphins (Tursiops truncatus) and two abundant fish species from this region in Chapter VI. Although this area has been called "pristine" by previous researchers, we demonstrate the relativeness of this term, revealing that even the "forgotten coast" has been influenced by these ubiquitous contaminants. We use these compounds as tracers to evaluate bottlenose dolphin habitat utilization patterns in Florida Big Bend coastal waters. We found that the dolphins we sampled have differences in concentrations and patterns of contaminant loading indicating preference for feeding in specific areas and bays. Our results agree with suggestions based on sighting information that animals from the east and west regions of our study site rarely comingle and that even in the western site, individual animals express preferences for either St Joseph or St Andrews Bay foraging grounds. / A Dissertation submitted to the Department of Oceanography in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Spring Semester, 2010. / Date of Defense: January 29, 2010. / Estuary, Stable Isotope Analysis, Food Web, Trophic Web, Apalachicola Bay, Florida / Includes bibliographical references. / Jeffrey P. Chanton, Professor Directing Dissertation; William T. Cooper, University Representative; Douglas P. Nowacek, Committee Member; John R. Kucklick, Committee Member; Yang Wang, Committee Member; William C. Burnett, Committee Member.

Baroclinic, geostrophic turbulence is random, chaotic flow characterized by significant vertical gradients in density (Bu << 1) in which rotation plays a major role (Ro << 1). In the presence of a large-scale background gradient of potential vorticity (a β-effect ), a symmetry-breaking occurs which admits anisotropy in the system. These conditions form the fundamental dynamical basis of many natural geophysical flows on a planetary scale (Rh << 1), and even fairly simple models of these phenomena can exhibit quite complex behavior. One such aspect that is common to these flows is that of multiple, zonal jets. These are spontaneous flow structures characterized by fast East-West (azimuthal) motion. This thesis describes the creation of multiple jets in the laboratory within a fully-stratified, baroclinically-forced fluid subject to rotation and a β-effect. By carefully controlling the forcing parameters, we observe the transition between a single “classical” baroclinic wave and regimes that closely resemble conditions of natural planetary flows. Observing this transition in the laboratory shows that the proposed scaling arguments are valid and have predictive power in the case of multiple zonal jets in a baroclinic fluid. Spontaneous eddy forcing of the mean flow is shown to be the ultimate driving force of the jets, whose evolution is observed in time. A long-duration drift in the jet structure is observed and quantified to be an order of magnitude less than the Rossby wave phase speed. A detailed quantitative analysis of the structure the flow field sheds further light. This is done through both a standpoint of the Eulerian flow fields, and the raw data associated with the (Lagrangian) tracks of neutrally buoyant particles within the flow. There is a significant transition of the power law scaling of Fourier spectra between dynamically significant scales. As the flow changes between experiments, the power law of the Eulerian spectra can change over particular scale ranges, which is direct evidence of a regime change. Access to raw Lagrangian tracks of the fluid allow a direct characterization of the flow field that is independent of the Eulerian. The structure function technique is introduced and shows a fundamental change in behavior between dynamic scales, and between experiments, in a way consistent with theory. A preliminary analysis is carried out of an experiment studying the competing mechanisms of buoyancy and wind forcing present on a single zonal jet. This is simulated in a rotating annulus of fluid by imposing a radial temperature gradient across the annulus gap, while applying mechanical forcing at the surface through the differential rotation of a rigid lid in contact with a surface layer of oil. A radially-sloping bottom creates a fluid depth gradient and simple topography in the form of five regularly spaced meridional ridges creates azimuthally varying f/h contours that steer the first-order flow. By varying the strength of wind and thermal forcing on the fluid, several regimes of flow are produced. Analysis of the Eulerian field shows the response of zonal transport and eddy kinetic energy to these different forcing regimes. The thesis concludes with a description of the development of an apparatus to push the observations into a more turbulent dynamical range. This includes information about the spin-up and maintenance of a large-scale sloping thermal gradient in the apparatus, as well as some preliminary results. / A Dissertation submitted to the Geophysical Fluid Dynamics Institute in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester 2018. / April 2, 2018. / Baroclinic Turbulence, Geostrophic Turbulence, Multiple Zonal Jets, Planetary Jets / Includes bibliographical references. / Kevin G. Speer, Professor Directing Dissertation; William M. Landing, University Representative; William K. Dewar, Committee Member; Philip G. Sura, Committee Member.

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 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. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2018. / July 5, 2018. / 2017, Harvey, Hurricane, HWRF, Secondary, Structure / Includes bibliographical references. / Jeffrey Chagnon, Professor Directing Thesis; Robert E. Hart, Committee Member; Philip Sura, Committee Member.

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 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. / A Dissertation submitted to the Geophysical Fluid Dynamics Institute in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester 2016. / March 23, 2016. / QBO, Tropics, Waves / Includes bibliographical references. / Ming Cai, Professor Directing Dissertation; Xufeng Niu, University Representative; Allan Clarke, Committee Member; Kevin Speer, Committee Member; Philip Sura, Committee Member.

Ensemble forecasts are the primary tool used operationally to assess forecast uncertainty. Studies of ensemble forecasts, however, have shown that forecast verifications too frequently lie outside of the ensemble's range of possibilities, meaning that uncorrected ensemble forecasts suggest more confidence than is justified. To make ensemble forecasts more representative of the actual range of possibilities, we present a technique to post-process ensemble forecasts by replacing member forecasts with verifications of what actually occurred when past forecasts were similar. To maximize the information that can be extracted from an archive of past forecasts and verifications, we allow analogs to come from different locations in space. We evaluated our procedure to post-process NCEP ensemble precipitation forecasts for the United States for 15-day periods in July 2005 and January 2006. Our analog correction technique significantly improved the ensemble's ability to forecast the probability of precipitation, in particular correcting the NCEP Global Ensemble's ``wet' bias at low precipitation amounts. Brier Skill Scores for 6-hour accumulated precipitation during the winter indicated that uncorrected ensemble forecasts were less skillful at predicting the probability of precipitation than forecasting zero precipitation as indicated by negative Brier Skill Scores (roughly -2.5). Post processed forecasts had Brier Skill Scores as high as 0.34. The tendency of the ensemble to underforecast heavy precipitation events, however, was not well corrected by our post-processing technique. Examinations of analog locations during heavy precipitation events indicated that analogs were taken from regions where precipitation patterns differed from those at the forecast point. This indicates that analogs must be chosen using more information than merely the similarity of ensemble precipitation forecasts to past forecasts. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Spring Semester, 2007. / Date of Defense: March 29, 2007. / Forecasting, Post-Processing, Ensemble Forecasts, Ensemble, Analogs / Includes bibliographical references. / Jon E. Ahlquist, Professor Directing Thesis; T. N. Krishnamurti, Committee Member; Xiaolei Zou, Committee Member.

Accurate hurricane intensity prediction is at the forefront of atmospheric science today, and improvements to mesoscale modeling of these storms continue to be major components of refining the accuracy of intensity forecasting. The primary goal of this study is to improve mesoscale modeling of hurricane intensity via the comparison of field campaign observations of Hurricane Erin 2001 from the Fourth Convection And Moisture Experiment (CAMEX-4) and Hurricane Dennis 2005 from the Tropical Cloud Systems and Processes (TCSP) mission with simulated results of improved microphysical parameterization in a mesoscale model that utilizes the Krishnamurti, et al (1991) technique of rain rate initialization (RRI). Comparison of the simulated results with field observations collocated with satellite observations provides a way to validate many different aspects of the simulated hurricane's structure and intensity. The mesoscale model used in this research is the Weather Research & Forecasting (WRF) model version 2.1 (ARW). Much of the existing microphysical parameterization of this model is built from results of mid-latitude observations. Substantial improvement to the model's intensity forecasting in the tropics can be made via proper parameterization of the model microphysics for hurricanes. With a foundation of results from other hurricane mesoscale modeling initial/boundary conditions, dynamics and physics studies, basic options for modeling hurricanes Erin (2001) and Dennis (2005) are chosen and held constant during a series of microphysical sensitivity experiments for each storm. These are specifically designed to isolate the individual effects of altering one microphysical parameter at a time on the hurricane's intensity forecast and are carried out in a doubly or triply nested way. The initial and boundary conditions used in the innermost grid with finer resolution are obtained from the respective outermost grids where rain rate initialization is invoked. All of the results are illustrated for the highest-resolution innermost domain, which is integrated using an explicit microphysics scheme. Each of these experiments are integrated for a forty-eight hour forecast period, adequately capturing the mature and intensification stages of the two hurricanes. Skill scores are obtained from the results of the two sets of experiments. Root Mean Square Errors (RMSE) and Anomaly Correlations (AC) are computed by comparing the model output of each experiment to NCEP's final analysis (fnl) available at one-degree horizontal resolution and six-hour temporal resolution interpolated to the respective model grid. Taking into account the way that each experiment performs in terms of simulated storm intensity as well as optimized RMSE and AC, the optimal combination of microphysical processes (i.e. melting, evaporation, fall speed of hydrometeors) for each storm is determined. Then a final forty-eight hour forecast of each hurricane is made utilizing this optimal microphysical parameterization combination. The results from each final run are compared to observations, skill scores are computed, and the final intensity improvements for both hurricanes Erin and Dennis are shown. The results of this study strengthen the evidence that RRI and proper microphysical parameterization in mesoscale hurricane modeling are both useful and effective techniques, and combine to improve hurricane intensity forecasting in a mesoscale model. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Fall Semester, 2007. / Date of Defense: October 26, 2007. / Modeling, Mesoscale, Forecast, Microphysics, Parameter / Includes bibliographical references. / Tiruvalam N. Krishnamurti, Professor Directing Thesis; Guosheng Liu, Committee Member; Paul Ruscher, Committee Member; Robbie Hood, Committee Member.

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