A two-phase study of the potential impact of Geosynchronous Imaging Fourier Transfer Spectrometer (GIFTS) radiance data to the prediction of strong convective events was developed. In the first phase of the project, a statistical analysis of six runs of the Fifth Generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5), version 3, was performed. These runs incorporate different size domains, numbers of vertical levels, numbers of nesting domains, and physical schemes. Using high-resolution National Center for Environmental Prediction (NCEP) Stage IV precipitation estimates, mesonet data, and radar reflectivity, it was determined that of all runs, one was chosen as being most appropriate for simulating GIFTS radiance. This run incorporates the simple ice microphysical scheme, the Grell cumulus scheme, the Blackadar planetary boundary layer scheme, and a simple atmospheric radiation scheme. Furthermore, this run was nested, with the mother domain (12-km resolution) of size 163 x 127 x 54 and the nested domain (4-km resolution) of size 103 x 127 x 54. In the second phase of the project, two sensitivity studies were carried out. In the first sensitivity study, the sensitivity of simulated GIFTS radiance to temperature and water vapor were examined. The 14 most sensitive channels within the GIFTS spectral range, out of 3,073, were chosen for further analysis. Through an analysis of an MM5 grid point that had relatively minimal cloud cover, it was determined that the most sensitive atmospheric layers at eight channels are in the lower troposphere (temperature) and lower to mid-troposphere (water vapor). At the other six, the most sensitive region is in the mid- to upper troposphere. The layers of maximum sensitivity are consistent with peaks of the weighting functions of these channels. The second sensitivity study examined the sensitivity of convective precipitation forecasts to the initial conditions of temperature and water vapor. The purpose of this study was to "bridge" the results of the first sensitivity study to the MM5 quantitative precipitation forecast (QPF) results. It was found that the most sensitive region is over the Central Plains of the United States and that the convective QPF is most sensitive to both water vapor content and temperature in the low-levels of the troposphere. Furthermore, temperature is deemed more sensitive to convective QPFs than water vapor. The results from these sensitivity tests, when linked together, demonstrate that GIFTS radiance at the eight wavenumbers most sensitive in the lower troposphere may be more effective to improve QPF than higher wavenumber radiance and that temperature in the Central Plains is the key meteorological variable to which the convective QPF is most sensitive. In a future four-dimensional variational data assimilation (4D-Var) study, simulated and real atmospheric observations from various sources will be assimilated into the MM5, with the GIFTS model representing the observation operator. Through this current study, a better sense of the utility of data from GIFTS to the forecasting of convective precipitation is ascertained, which would help streamline the 4D-Var study. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Masters of Science. / Degree Awarded: Spring Semester, 2005. / Date of Defense: April 11, 2005. / Response Function, Convection, Oklahoma, Kansas, Brightness Temperatures / Includes bibliographical references. / Xiaolei Zou, Professor Directing Thesis; Robert Hart, Committee Member; Paul Ruscher, Committee Member.

This study computes statistical forecasts of monthly and three-monthly rainfall for seven regions of Florida defined by the National Climatic Data Center. First, time-lagged auto- and cross-correlations are computed involving monthly regional rainfall time series and various potential predictors. Various statistical monthly forecasting models are then built for each of the seven regions based on teleconnection indices and principal components of monthly heights of the global 500 hPa pressure surface. To compare these forecasts to those of the Climate Prediction Center (CPC), the forecasts are categorized into terciles, corresponding to the upper, middle, and lower thirds of the climatological distribution of rainfall for each of the twelve months for each region. Following CPC, these are scored with the Heidke Skill Score. The variability of model coefficients and forecast skill is measured using cross-validation. The monthly Heidke Skill Score is low but generally better than a climatological forecast, which is CPC's standard of comparison. For most months and forecast regions, the Heidke Skill Score increases if a forecast for the middle tercile is replaced by a forecast that all three terciles are equally likely. Averaged over the year, the Florida Panhandle has the lowest monthly forecast skill, and Southwest Florida has the highest. April and May as well as September and October have low skill statewide. These times of year are associated with shifts in the prevailing winds as well as the El Nino-Southern Oscillation (ENSO) phase. Higher skills are obtained when forecasting the next three month's total precipitation than the next month's total precipitation. This increase in skill is largely due to the important of ENSO as a predictor and that ENSO is less noisy across three months than one month. A summer low in the forecast skill for three month's rain is due to the minimum in time-lagged correlation between late spring and summer. A middle tercile forecast for three-month rainfall is more likely to verify than a middle tercile forecast for one-month rainfall. / 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, 2009. / Date of Defense: August 6, 2009. / Florida Rainfall, Statistical Forecasting, Long-Range Forecasting, Seasonal Forecasting / Includes bibliographical references. / Jon E. Ahlquist, Professor Directing Thesis; Philip Sura, Committee Member; Robert Hart, Committee Member.

There has been great energy focused on tropical cyclone intensity forecasting over the past thirty years. Toward the goal of providing more accurate intensity forecasts, the role of the environment of a tropical storm has been studied at great length over the past few years while the storm itself has not. There remains considerable work left toward understanding how the tropical cyclone structure itself can be used to aid intensity forecasting. One step toward this goal for the Atlantic is by dissecting a climatology of reconnaissance vortex message reports from the Atlantic basin between 1989 and 2005. Such an analysis will permit the comparison of tropical cyclone core structure measurements to know future intensity change. This vortex message data, which is collected from dropsondes and radar during flights into tropical disturbances, includes eye size, pressure, eye temperature, eye dewpoint, maximum flight level winds and other pertinent information. The number of occurrences for each vortex message characteristic as well as frequency plots of eye type, Julian day, latitude, longitude, temperature, dewpoint, and intensity change as a function of mean sea level pressure (MSLP) and eye size were created. The composite mean eyewall cycle was analyzed, along with the cycles of concentric eyewalls and elliptical eyewalls. Based on this vortex message climatology and analysis, an eyewall phase diagram was developed that graphically shows the evolution of a storm. These eyewall phase diagrams show how eyewall cycles evolve in time using mean MSLP, mean eye size, concentric eyewall frequency, and elliptical eyewall frequency data. Case studies include analysis of a storm undergoing an eyewall replacement cycle (Rita 2005), a rapidly weakening storm (Charley 2004), and a rapidly intensifying storm (Wilma 2005). It was discovered in this study that core storm data collected from vortex data messages could be used to confirm theories on tropical cyclone intensity. Preliminary attempts at simple forecasts comparing eye characteristics and future intensity change were done. Indeed, short-term forecasts of intensity change should utilize storm-specific structure, beginning with an analysis of that structure in intensification versus weakening events. Further work involving pattern matching trajectories and trajectory segments to forecast future storm trajectory in the eyewall phase diagram may lead to helpful analog tropical cyclone intensity forecast guidance. / 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: November 6, 2007. / Tropical Cyclone, Climatology, Vortex Data Message, Forecasting / Includes bibliographical references. / Robert Hart, Professor Directing Thesis; Carol Anne Clayson, Committee Member; Henry Fuelberg, Committee Member.

Almost daily summer time thunderstorms in central Florida frequently halt outdoor operations, requiring that one wait some prescribed time after an observed lightning flash to safely resume activities. This is an especially important problem for the U.S. Air Force’s 45th Weather Squadron (45WS). Prior research suggests that these wait times might be safely shortened by observing reflectivity values and hydrometeor type with radar to safely predict that lightning has ended for a particular isolated thunderstorm. The main goal of this study was to create a usable operational tool that would create probabilistic guidance for the 45WS to use for determining total lightning cessation for isolated storms. The study analyzed dual-polarized radar data from isolated thunderstorms to develop probabilistic lightning cessation guidance for the 45WS. We tracked 184 isolated storms in central Florida at 1 min intervals using radar and lightning detection systems including radar reflectivity and hydrometeor classification at isothermal levels. For each isolated storm we investigated its maximum reflectivity and graupel presence at the 0, -5, -10, -15, and -20°C levels and composite (maximum) reflectivity. A random sample of all the 1 min interval data was used to train a generalized linear model (GLM) to make a probabilistic prediction that cessation had occurred. The GLM revealed that the most statistically significant predictors for lightning cessation were maximum reflectivity at the composite and 0 °C levels along with graupel presence at the -5, -10, -15, and -20°C levels. The GLM was trained with 1000 random samples of minutes to bootstrap the results, with the median values of the final set of predictor coefficients used to calculate probabilities that cessation had occurred at that minute. Forecast verification statistics from another random sample of tracked minutes then were used to analyze the performance of the GLM with different probability thresholds (95.0%, 97.5%, and 99.0%) for determining lightning cessation. Applying this cessation guidance from our GLM as though the storms were occurring in real time revealed that only about 1% of the 184 storms in our data set had observed lightning after the GLM suggested cessation had already occurred, an event which would threaten life and property. Even the median of the most conservative probability threshold (99.0%) improved on the guidance currently being used by the 45WS, while the 95.0% probability guidance had a median wait time of just 9 min after cessation. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the Master of Science. / Summer Semester 2017. / July 7, 2017. / Includes bibliographical references. / Henry E. Fuelberg, Professor Directing Thesis; Robert Hart, Committee Member; Jeffrey Chagnon, Committee Member.

According to the United States Department of Transportation (US DOT), an average of over 28,000 crashes and almost 500 deaths annually occurred as a result of fog-related vehicular accidents. In Florida, the January 2008 and January 2012 fog-related multi-car accidents claimed the lives of four and eleven people, respectively. A more effective fog warning system could include the use of remote sensing. The ground observation sites used to detect fog statewide are both widely and unevenly dispersed. Many high-traffic areas affected by fog are not monitored by ground equipment, leading to poor forecasting and detection of fog in these areas. A combination of both ground observations and remote sensing may lead to better statewide fog detection and forecasting. A bispectral nighttime fog detection technique is used to determine the presence of fog across the state of Florida. This technique uses brightness temperature differences (BTD) between two infrared (IR) channels. The performance of the technique is validated through the use of six months of observation data from AWOS/ASOS sites across the state. An optimum fog detection threshold is found based on the BTD values. Both the optimum threshold and the skill of the optimum threshold are compared to a previous study which used a geostationary satellite for fog detection. The bispectral technique shows little skill, with a large amount of misses and false detections of fog. The low skill can be attributed to the fact that MODIS makes only one nighttime pass which may not necessarily be when fog has formed. The increased spatial resolution of the MODIS sensor over the previous generation GOES Imager does not make up for the decreased number of nighttime satellite passes in a given day. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the Master of Science. / Summer Semester 2017. / June 30, 2017. / brightness temeprature difference, Florida, fog, fog detection, MODIS, remote sensing / Includes bibliographical references. / Peter S. Ray, Professor Directing Thesis; Guosheng Liu, Committee Member; Vasu Misra, Committee Member.

The Sahel and Guinea Coast regions of Africa have long been the subject of studies on interannual and intraseasonal rainfall variability. The unique geography, monsoon circulation regime, and a variety of climatic teleconnections produce large variations in year-to-year rainfall across the region. These large fluctuations in rainfall can have devastating effects on the inhabitants of West Africa, who rely on the rainfall for both agriculture and human consumption. Thus, a better understanding of the nature of rainfall variability in the area is warranted. The El Niño/Southern Oscillation (ENSO), one of the most studied climate phenomena, is known to have far-reaching impacts on weather across the globe. This study provides one of the most comprehensive and complete analyses of the relationship between ENSO and rainfall across the Sahel and Guinea Coast to date. Several previous studies have found little connection between Sahel rainfall and ENSO phase, while others have suggested that ENSO can result in changes within the monsoon circulation and cause a reduction in Sahel rainfall during El Niño years. By utilizing the largest and longest dataset of rainfall gauge data available, this study provides an analysis of rainfall anomalies experienced during El Niño and La Niña years from 1921-2012 in the context of a major shift in the rainfall regime that occurred around the year 1968. This research finds that before 1968, rainfall during the peak Sahel rainy season in El Niño years was below normal, but above normal in the Guinea Coast. The same is observed after 1968, but the anomalies are of stronger magnitude than before 1968, suggesting an increased ENSO-Sahel rainfall teleconnection after 1968. Similar intensifications of the El Niño signal are observed in other seasons as well. In general, opposite rainfall anomalies were observed during La Niña years when compared to El Niño years. An increase in La Niña influence in more recent years is also detected. An analysis of the consistency of the ENSO signal suggests that the ENSO rainfall response is most consistent in areas of the Sahel during the JAS (-1), OND (-1), JAS, and OND seasons. Evidence also suggests that there was a weakening of the Sahel/Guinea Coast dipole after 1968. Finally, an analysis of upper air circulations shows few differences in zonal winds during El Niño and La Niña years versus non-ENSO years, suggesting the relationship between ENSO and Sahel rainfall may be fairly weak. There are some subtle differences seen, however, when comparing years before 1968 to years afterwards that were consistent with the observed rainfall anomalies in certain seasons. This study concludes that the rainfall response to El Niño and La Niña events in the Sahel and Guinea Coast as a whole is relatively inconsistent, but there was some meaningful connection found between ENSO and rainfall in the Sahel during certain seasons outlined above. This relationship intensified after the 1968 rainfall regime change, consistent with findings from previous studies. / 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 2017. / July 10, 2017. / Includes bibliographical references. / Sharon Nicholson, Professor Directing Thesis; Philip Sura, Committee Member; Guosheng Liu, Committee Member.

Simulations are conducted using the Weather Research and Forecasting (WRF) model in a nested domain having horizontal grid lengths of 12 km, 4 km, and 1.33km, in order to establish the dynamic and thermodynamic controls that three popular cloud Micro Physics (MP) schemes exert over the sea-breeze-forced convection commonly seen over the Cape Canaveral region. Experiments focus on a period from 12-20 Aug 2016 in a regime dominated by high pressure and southeasterly flow; simulations were initialized at 06Z on each day during the week and run for a period of 24 hours. One double-moment and two single-moment MP schemes were employed in the simulations for comparison. Results demonstrate that the MP scheme can have a substantial influence on regional convective simulations - large enough to shift the trigger and location of convection. Large differences in domain averaged bulk hydrometeor quantities are found, particularly in the vertical profile of the rain bulk mixing ratio. Simulations employing the double moment scheme systematically underestimate the total precipitation throughout each day but also systematically produced stronger cold pools. Plots of vertical cloud water and potential temperature indicate a greater concentration of cloud droplets at an elevation of 2-4 km and a much larger latent heating when the double moment scheme was used. Modulation of the latent heat release within the double moment scheme is hypothesized to occur from the Drop Size Distribution (DSD), and the prescribed Cloud Condensation Nuclei CCN parameter used to calculate this distribution. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the Master of Science. / Spring Semester 2017. / April 25, 2017. / Meteorology / Includes bibliographical references. / Jeffery M. Chagnon, Professor Directing Thesis; Robert E. Hart, Committee Member; Henry E. Fuelberg, Committee Member.

Both intuition and previous statistical analysis suggests that in general, hurricane size tends to increase with intensity. However, such statistical correlation, including the statistical significance and even the sign of the correlation, between hurricane size and intensity strongly depends on the sample hurricanes in the data pool for the correlation analysis. For example, there are ample instances when a hurricane at different times can have a similar size but differ in terms of intensity and vice versa. Therefore, predictions based on intuition or statistics often fail when considering an individual hurricane. In this thesis research, we attempt to apply a theoretical model in conjunction with observational case studies to gain insight on the main factors that make the relationship between both hurricane size and intensity, obscured. This theoretical model will apply an analytical analysis of the inertial instability neutral radial profile of an isolated gradient-wind balanced circular vortex in an f-plane shallow water equation model, which shows that the relationship between the size and the maximum tangential wind speed is not unique, because the size also depends on the radius of maximum wind. The radial profile of wind under neutral conditions of inertial instability reveals that hurricane size and intensity can have either a positive, near-zero, or negative correlation depending on the sample of hurricanes in the dataset from which such correlation is obtained. The main conclusion derived from the theoretical model is that the relationship between hurricane size and intensity can be obscured due to only one specific factor (i.e., the radius of maximum wind) that also influences the size. The theoretical model also predicts that the latitudinal position only weakly obscures the relationship, as long as the hurricane is not too close to the equator. We have examined whether the size inferred from the radial profile of inertially neutral wind would be able to capture its observational counterparts. Specifically, we examined five selected hurricanes derived from the Extended Best Track (EBT) Data, namely Katrina (2005), Ike (2008), Gustav (2008), Sandy (2012), and Joaquin (2015). We have performed a correlation analysis on the observed size and the size predicted by the simple theoretical model by using the information of maximum wind speed and its radius of each of the five hurricanes throughout the phases of each tropical cyclone’s (TC) life cycle. We found that the size obtained from the barotropic inertially neutral radial profile underestimates the size of observed hurricane by a factor of 2-2.5. This suggests that the observed hurricane wind’s radial profile does not follow angular momentum conservation or an air parcel would lose angular momentum as it converges towards the eyewall, mainly due to surface drag and eddy-mixing processes. This finding also implies that there are other parameters besides these three factors (intensity, radius of maximum wind, and latitude) that influence an individual hurricane size. This implies that the relationship between size and intensity is more complex than that predicted by the simple theoretical model. Our analysis suggests that about 1/3 (48 out of 174) of the observed cases show that other factors may strongly affect hurricane size. By removing these 48 data points that are indicative of possible strong impacts from the external factors, the R-squared value of the linear regression line between the observed size and the size predicted by the theoretical model increases substantially (from R2 = 46.3% to 71.5% on average). The inspection of the timing and location of these “external” data points indicate that they often occur in situations when (i) encountering big islands or land mass (e.g., Cuba for Ike) and (ii) undergo a very rapid weakening/intensifying transition (Joaquin). Therefore, the size information predicted by the simple theoretical model does capture the size record for most the track records (126 out of 174), suggesting that the most important factors that influence hurricane size are both maximum wind speed and the radius of maximum wind speed. / A Thesis submitted to the Department of Earth, Oceanic and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2017. / June 22, 2017. / Intensity, Size, Tropical, Tropical Cyclone / Includes bibliographical references. / Ming Cai, Professor Directing Thesis; Robert Hart, Committee Member; Guosheng Liu, Committee Member.

Severe supercell thunderstorms exhibit rotation which aids in organization and maintenance of the storms. The effects of helicity and diabatic heating on the structure of potential vorticity (PV) in a supercell thunderstorm is examined through simple theoretical analysis using the linearized form of the Boussinesq system of equations and using sensitivity experiments in the Weather Research and Forecasting (WRF) model. The linear analysis shows that in the presence of helicity, a region of diabatic heating will favor one PV pole, resulting in storm rotation. In an environment with no helicity, a PV dipole will straddle the region of diabatic heating. The amplitude of the diabatically generated PV is regulated by the ratio H/U^2 where H is the helicity and U is the component of wind directed parallel to the background horizontal vorticity. This theoretical analysis of PV informs the design of five different idealized WRF experiments which demonstrate the role of helicity and latent heating in storm organization under differing environmental wind conditions. The WRF sensitivity tests confirm that a larger (smaller) H/U^2 results in more (less) storm rotation. This thesis offers a new PV perspective on the origin of storm scale rotation in convective environments and highlights the role of microphysical processes and latent heating in storm rotation. / 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 2017. / July 10, 2017. / Helicity, Latent Heating, Potential Vorticity, Storm Rotation, WRF / Includes bibliographical references. / Jeffrey Chagnon, Professor Directing Thesis; Henry Fuelberg, Committee Member; Robert Hart, Committee Member.

A novel method for assimilating precipitation observations into a numerical weather prediction model is presented and evaluated for a case study of a monsoon rainfall event over the Asian subcontinent. The method, known as physical initialization (Krishnamurti et al. 1991), involves the iterative adjustment of the vertical moisture profile towards a configuration that would permit simulated precipitation where there is observed precipitation. The physical initialization procedure was incorporated into the Weather Research and Forecasting (WRF) model. Evaluation of the technique was accomplished through the comparison of two simulations: one with the physical initialization and one without. Both simulations were evaluated against TRMM rainfall. The impact of physical initialization was shown to be beneficial to the two-day typical Indian Summer Monsoon case study with respect to the rainfall forecast skill as well as the mesoscale circulation and vertical redistribution of moisture. Specifically, the correlation between simulated and observed 3-hour accumulated precipitation is higher throughout the two-day forecast period in the run with physical initialization. The probability distribution of rainfall amounts in the run with physical initialization was also more similar to the observations, whereas the control WRF run exhibited a large bias of widespread light to moderate rain. Additionally, the run with physical initialization improves the forecast location of mesoscale precipitation features and removes regions of spurious rain from the forecast. Simulations were conducted and evaluated for this case only. / 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 2017. / July 7, 2017. / Includes bibliographical references. / Jeffrey Chagnon, Professor Directing Thesis; Robert Hart, Committee Member; Vasu Misra, Committee Member; Robert Ross, Committee Member.