The rapid development and sub-synoptic scale nature of the Genoa low in the Mediterranean Sea poses a forecasting challenge for United States Air Force (USAF). The Genoa low is a high-impact event for several Department of Defense (DOD) locations located in southern Europe, especially in the Po River Valley of northern Italy. This study evaluates the predictability and dynamics of the Genoa low extending to a 4-day event lead time as is required by the mission protocols at the affected locations. Two Genoa low case studies are analyzed: 16 Feb 2015 (case 1), and 13 July 2016 (case 2), using the COnsortium for Small-scale MOdeling Limited-area Ensemble Prediction System (COSMO-LEPS). Ensemble prediction systems provide a range of possible forecast outcomes given the uncertainty in initial conditions, boundary conditions, as well as model physics. As such, ensembles are used to assess and analyze the predictability of the Genoa low. The analysis demonstrates several key findings concerning the Genoa low. The Genoa low is only weakly predictable at a lead time of 4 days. It is shown that only a small fraction of ensemble members (approximately 25%) met the Genoa low verification thresholds at this lead time. Ensemble spaghetti plots and maps of the ensemble variance show that the possibility of low formation at longer lead times is most effectively visualized using maps of ensemble variance. Traditional postage-stamp plots and minimum MSLP plots contain too much noise and variability to permit a forecaster to extract a signal indicating possible low formation. The formation of the Genoa low is associated with strong mistral winds. It is demonstrated that all ensemble simulations that were successful in identifying cyclogenesis also produce strong mistral winds, i.e., the strength of the mistral winds is anti-correlated to the minimum MSLP of the Genoa low. This linkage implies a potential dynamical connection between the two features. Further investigation shows that the mistral jet may exert an organizing influence on the Genoa low via a vorticity seeding mechanism. Time-lagged correlations show that the mistral jet amplifies several hours prior to cyclogenesis. The amplification is associated with mesoscale vorticity generation on the eastern periphery of the jet. These vorticity centers were subsequently shed into the target region where cyclogenesis occurs. Such a small-scale and rapid-developing dynamical link between the mistral winds and the Genoa low implies a limit on the predictability of the Genoa low. This study concludes that weather forecasting operations in the USAF would benefit from expansion of current ensemble prediction systems, not only for the purpose of improving the Genoa low forecast process and performance but also to better inform the mission planners of the limitations and uncertainties of predicting the Genoa low. / A Thesis submitted to the Department of Earth, Ocean, & Atmospheric Science in partial fulfillment of the Master of Science. / Spring Semester 2017. / March 30, 2017. / COSMO-LEPS, Ensemble Forecasting, Genoa Low, Predictability / Includes bibliographical references. / Jeffrey Chagnon, Professor Directing Thesis; Robert Hart, Committee Member; Vasu Misra, Committee Member.

At the same temperature, below 0oC, the saturation vapor pressure (SVP) over ice is slightly less than the SVP over liquid water. Numerical models use the Clausius-Clapeyron relation to calculate the SVP and relative humidity, but there is not a consistent method for the treatment of saturation above the freezing level where ice and mixed-phase clouds may be present. In the context of current challenges presented by cloud microphysics in climate models, we argue that a better understanding of the impact that this treatment has on saturation-related processes like cloud formation and precipitation, is needed. This study explores the importance of the SVP calculation through model simulations of the Indian Summer Monsoon (ISM) using atmosphere-only simulations with the Regional Spectral Model (RSM) and RSM coupled to the Regional Ocean Modeling System (RSM-ROMS). Atmosphere-only simulations are conducted with two saturation parameterizations. In one, the SVP over liquid water is prescribed through the entire atmospheric column (woIce), and in another the SVP over ice is used above the freezing level (wIce). When SVP over ice is prescribed, a thermodynamic drying of the middle and upper troposphere above the freezing level occurs due to increased condensation. In the wIce runs, the model responds to the slight decrease in the saturation condition by increasing, relative to the SVP over liquid water only run, grid-scale condensation of water. Changes in the cloud layer amounts in the wIce simulation cause in increase in the net heat flux (NHF) at the surface of 2-3 W/m2 over the Arabian Sea (AS) and a decrease of similar magnitude over the eastern equatorial Indian Ocean (EEIO). Motivated by these NHF changes the wIce and woIce experiments were repeated in the coupled simulations. With coupling added, the ocean is allowed to respond to any NHF changes; however we find that the NHF difference between wIce-woIce over the AS is near zero. It is proposed that with the inclusion of air-sea coupling the atmospheric and oceanic response to changes in the SVP is damped relative to the forced RSM integrations. The importance of air-sea interaction for the northward propagation and evolution of the Indian monsoon intrareasonal oscillation (ISO) is examined through a comparison between the uncoupled and coupled simulations, and the observed ISO. It was found that the observed ISO contains a robust air-sea interaction during its evolution which would suggest that coupling is required to simulate the observed relationship between the ocean and atmosphere during the ISO. However, the uncoupled simulations show the ability to simulate realistic amplitude ISOs without coupling to the ocean, suggesting that there is an internal atmospheric component that is important for simulating the observed ISO period and amplitude. / 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. / Spring Semester 2018. / April 9, 2018. / Boreal Summer Intraseasonal Oscillation, Cloud Scheme, Indian Monsoon, Saturation Vapor Pressure / Includes bibliographical references. / Vasubandhu Misra, Professor Directing Dissertation; Sachin Shanbhag, University Representative; Mark Bourassa, Committee Member; Robert Hart, Committee Member; Guosheng Liu, Committee Member.

The African Easterly Jet (AEJ) is one of the phenomena driving regional as well as global atmospheric circulation. Specifically, within the Sahel region, the AEJ and African Eastern Waves (AEWs) are main features that are linked and associated with the West African Monsoon. Both features determine rainfall and tropical cyclone development in this region. For certain years, the AEJ has a double core structure during the month of August when the jet is the strongest. The goal of this study is to identify distinct cases of the AEJ structure and determine the possible effect on AEW development. For this study, zonal and meridional wind data at 600 hPa was obtained from NCEP reanalysis during the month of August from 1948 to 2016. Maps of zonal wind were made to show the structure of the AEJ. Hovmöller diagrams of the 2.5 to 6-day meridional wind and maps of meridional wind variance were made to show the strength and track of AEWs. Results identified distinct cases where the structure of the AEJ deviated from its long-term mean, including the western (eastern) core being located north relative to the eastern (western) core. The double core cases with the southward eastern core has significantly stronger AEW activity with longer average tracks. However, on inter-annual scales, there is not a strong link between the AEW activity and east Atlantic tropical cyclone activity. The difference between the cases provide valuable insight about the relationship between the AEJ, easterly waves and tropical cyclone formation at the West African coast. / 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. / Spring Semester 2018. / April 5, 2018. / Includes bibliographical references. / Sharon E. Nicholson, Professor Directing Thesis; Jeffrey Chagnon, Committee Member; Robert Hart, Committee Member.

The 10–20-day mode of surface winds is examined in the Indian Ocean, with special reference to the Arabian Sea, the Bay of Bengal, and the equatorial Indian Ocean during a strong (1994), weak (2002), and normal (1995) Indian summer monsoon. The winds are from the Cross Calibrated Multi-Platform (CCMP) gridded wind product version 2.0. Results indicate the 10–20-day mode of latitudinally averaged surface winds have zonal propagation in the western Indian Ocean (west of 75°E) and the signal appears stationary in the eastern Indian Ocean (east of 75°E) during May through September. The meridional propagation of the 10–20-day mode of longitudinally averaged surface winds appears weak during summer monsoon periods. The 10–20-day mode of surface winds in the Arabian Sea and the Bay of Bengal is more energetic than in the equatorial Indian Ocean. The signal of the 10–20-day mode appears more robust during a strong monsoon than during a weak monsoon in the Arabian Sea; however, no significant difference is found in the Bay of Bengal and equatorial Indian Ocean between strong and weak monsoons. Ensemble empirical mode decomposition (EEMD) analysis is used on a time series from the Arabian Sea to create an index for the 10–20-day mode in surface winds. Using this index, 75 cases of 15-phase 10–20-day events are identified and used to create composites of surface winds. Through these composites, a positive surface wind anomaly is found to appear at 60°E, centered on 15°S, and propagate zonally eastward to 90°E before reflecting back to propagate westward and then disperse off the coast of Madagascar. It is proposed that this oscillating positive wind anomaly is a feature of the southernmost cell of the 10–20-day convective double-cell structure that has extended farther south into the southern Indian Ocean and that this mode connects the Arabian Sea and southern Indian Ocean through the Somali Jet and surface winds. / 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. / June 28, 2018. / Includes bibliographical references. / Mark A. Bourassa, Professor Directing Thesis; Vasu Misra, Committee Member; Zhaohau Wu, Committee Member.

This study examines the predictability of the Florida State University/Center for Oceanic and Atmospheric Prediction Studies (FSU/COAPS) climate model, and is motivated by the model's potential use in crop modeling. The study also compares real-time ensemble runs (created using persisted SST anomalies) to hindcast ensemble runs (created using weekly updated SST) to asses the effect of SST anomalies on forecast error. Wintertime (DJF, 2 month lead time) surface temperature and precipitation forecasts over the southeastern United States (Georgia, Alabama, and Florida) are evaluated because of the documented links between tropical Pacific SST anomalies and climate in the southeastern United States during the winter season. The global spectral model (GSM) runs at a T63 resolution and then is dynamically downscaled to a 20 x 20 km grid over the southeastern United States using the FSU regional spectral model (RSM). Seasonal, monthly, and daily events from the October 2004 and 2005 model runs are assessed. Seasonal (DJF) plots of real-time forecasts indicate the model is capable of predicting wintertime maximum and minimum temperatures over the southeastern United States. The October 2004 and 2005 real-time model runs both produce temperature forecasts with anomaly errors below 3°C, correlations close to one, and standard deviations similar to observations. Real-time precipitation forecasts are inconsistent. Error in the percent of normal precipitation vary from greater than 100% in the 2004/2005 forecasts to less than 35% error in the 2005/2006 forecasts. Comparing hindcast runs to real-time runs reveals some skill is lost in precipitation forecasts when using a method of SST anomaly persistence if the SST anomalies in the equatorial Pacific change early in the forecast period, as they did for the October 2004 model runs. Further analysis involving monthly and daily model data as well as Brier scores (BS), relative operating characteristics (ROC), and equitable threat scores (ETS), are also examined to confirm these results. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Masters of Science. / Degree Awarded: Fall Semester, 2008. / Date of Defense: August 13, 2008. / Crop Models, Skill Scores, Seasonal Prediction, Extreme Events / Includes bibliographical references. / James J. O'Brien, Professor Co-Directing Thesis; Jon E. Ahlquist, Professor Co-Directing Thesis; Paul H. Ruscher, Committee Member; Timothy E. LaRow, Committee Member.

Many studies have been conducted on the satellite remote sensing of rainfall, but not on the remote sensing of snowfall. To obtain a global view of snowfall in a timely matter, passive high frequency microwave satellite measurements must be used. Therefore, an accurate algorithm for detecting and retrieving snowfall on a global scale is needed. In developing this algorithm, it is important to account for the snow scattering signature which reduces the upwelling emission signal from the ocean surface observed at the top of the atmosphere. However, the emission due to cloud liquid will increase the upwelling radiation, therefore masking the snow scattering signature. Thus, cloud liquid within snow clouds must be understood. In this study, data from the Cloud Profiling Radar on CloudSat and AMSR-E on Aqua are used to investigate the quantity of cloud liquid for snowfall events. The relationship between cloud liquid and echo top, cloud thickness, and two-meter air temperature is determined. The quantity of cloud liquid present in stratiform and convective snowfall events is also compared. Using snowfall profiles obtained from the reflectivity profiles provided by CloudSat, the masking effect of cloud liquid on the snow scattering signature on vertical and horizontal brightness temperature is determined for snow events with various surface snowfall rates. The masking effect on a parameter designed to reduce the emission signal due to cloud liquid, the polarization corrected temperature, is also tested. / 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, 2010. / Date of Defense: March 23, 2010. / Snowflake, Emission, Ice, Liquid Water Path, Snow / Includes bibliographical references. / Guosheng Liu, Professor Directing Thesis; Mark Bourassa, Committee Member; Henry Fuelberg, Committee Member.

The landfalls of extreme hurricane events in recent years reveal the need for more accurate predictions of winds during landfalling tropical cyclone events to help reduce property damage. The goal of this study is to develop a high-resolution surface wind exposure model that incorporates an effective roughness model. In this study, the wind model calculates flight- level winds of a rankine- like vortex in a simple synthetic large-scale environment at a 1 km resolution. The flight-level winds are then reduced to 10 m using a reduction scheme based on GPS dropwindsonde profiles. The roughness component calculates the effective roughness length using a radial weight function based on the source area model developed by Schmid and Oke, with an upwind fetch of 5 km. The weight function is dependent on the distance from sensor, sensor height, surface roughness (approximately 100 m resolution), and the Monin-Obukov length. The weighted average of roughness values is taken over 8 possible wind directions to give a more sophisticated effective roughness length for all land points. The high-resolution wind exposure model provides realistic analyses for hurricane Andrew (1992), Erin (1995), Kate (1985), and Donna (1960) at the time of their Florida landfalls. It is also useful for recreating historical hurricane case studies. There is a potential for further development into a real-time analysis and forecasting tool during tropical cyclone landfall events. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Masters of Science. / Degree Awarded: Fall Semester, 2003. / Date of Defense: September 23, 2003. / Hurricane model, risk management, wind model / Includes bibliographical references. / T. N. Krishnamurti, Professor Directing Thesis; Paul H. Ruscher, Committee Member; Philip Cunningham, Committee Member; Steven Cocke, Committee Member.

An adjoint mesoscale modeling system based on the Naval Research Laboratory's Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS) atmospheric model was created for use in sensitivity and data assimilation experiments. In addition to the tangent linear and adjoint models of the dynamical core of the COAMPS model, the system includes the tangent linear and adjoint models of the boundary layer turbulent kinetic energy, cumulus, and explicit moist physics parameterizations. The inclusion of these adjoint model physics schemes allows for assimilation experiments involving rain-affected observations such as microwave radiances. A radiative transfer model which includes the effects of hydrometeors on atmospheric radiation was linked to the adjoint modeling system to assimilate microwave radiance observations. Probability distribution functions of model-produced and SSM/I observed brightness temperatures show that the mesoscale prediction overestimates the areas of precipitation, but overall matches the microwave observations quite well. Furthermore, estimates of vertical background error covariance matrices for the hydrometeor variables were calculated using differences between model forecasts which utilized different explicit moisture schemes. The statistics of the differences between the forecasts were assumed to be the same as the statistics of the background error for these variables. The inverse of these matrices (which are needed for data assimilation) were computed using Singular Value Decomposition. Only the largest singular value was kept in calculating the inverse. This ensured that all of the elements of the inverse matrix were non-negative. Finally, microwave radiance observations for Hurricane Bonnie (1998) were assimilated in a 4-dimensional variational data assimilation framework using the COAMPS adjoint model. The model-produced radiances calculated from the analysis fields after the assimilation process match the observations well for the lower frequency channels which are sensitive to liquid precipitation and water vapor. In the highest frequency channel, where the presence of frozen hydrometeors can have a large impact on the radiance value, the match between the analysis and the observations was not as good. The forecasted hurricane was slightly stronger after the assimilation of microwave radiances in terms of both maximum surface windspeed and minimum central sea level pressure, and some improvement was seen in radiance space as well. More observations from within the hurricane, which will improve the analysis of other variables, will most likely be needed to see a greater forecast impact from the assimilation of these observations. / A Dissertation submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Spring Semester, 2005. / Date of Defense: March 29, 2005. / 4D-Var, brightness temperatures / Includes bibliographical references. / Xiaolei Zou, Professor Directing Dissertation; Ionel Michael Navon, Outside Committee Member; James J. O'Brien, Committee Member; Guosheng Liu, Committee Member; T.N. Krishnamurti, Committee Member.

This research focuses on the transport of chemical species to the upper troposphere/lower stratosphere (UTLS) by tropical cyclones (TCs). Species such as carbon monoxide, nitrogen oxides, and ozone have been found to exert a greater influence on climate change at these high altitudes than if remaining near the surface. Typhoon Mireille (1991) is examined in the western North Pacific (WNP) Ocean basin using in situ aircraft-derived chemical data from NASA's Pacific Exploratory Mission-West A field project. The Weather Research and Forecasting (WRF) model was used with chemistry (WRF-Chem) at an innermost grid spacing of 3 km to explicitly resolve the convection being studied. Results show that pollution from distant sources is ingested by Mireille and subsequently lofted by eyewall convection to the UTLS, enhancing concentrations in this region. Flux calculations suggest that a strong TC, such as Mireille, can impact UTLS chemistry as much as a continental middle latitude cyclone. Furthermore, overshooting cells in Mireille produced chemical flux density values at the tropopause level as much as 10-20 times greater than that of the TC as a whole. Thus, although the overshooting tops comprise only a small area of the total TC, they transport large quantities of gaseous species to the UTLS because of their very strong updrafts. Results also suggest that millions of cars and/or several power plants would need to be hypothetically placed in the upper troposphere to have the same impact on chemical concentrations as Mireille. This demonstrates the transport strength of the TC as a whole. Improved understanding of atmospheric chemistry in the WNP basin is important, especially in the context of increasing Asian emissions and a changing climate. Furthermore, since it has been hypothesized that global warming will lead to more intense storms, it is important to understand TCs’ role in chemical transport. / 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. / Summer Semester 2017. / August 3, 2017. / Atmospheric Chemistry, Climate, Deep Convection, Mesoscale Modeling, Tropical Cyclones / Includes bibliographical references. / Henry E. Fuelberg, Professor Directing Dissertation; David Van Winkle, University Representative; Mary Barth, Committee Member; Robert E. Hart, Committee Member; Philip Sura, Committee Member; Guosheng Liu, Committee Member.

Tropical waves are important tropical and global weather/climate systems as well as carriers for redistributing global energy. For decades, a multitude of tropical wave theories that attempt to explain the origins and maintenance mechanisms of tropical waves and the interactions between them and other tropical systems have been put forth by scientists. Partly due to the lack of effective analysis tools, observational studies of tropical waves have not been comprehensive enough, leaving many of the proposed theories unverified. For example, Fourier spectrum analysis based methods can hardly be used to obtain the accurate climatology of tropical waves because of the impacts of locality. This study serves two purposes: (1) To introduce and develop novel dynamics-based effective methods and to tailor them for isolating spatiotemporally local tropical waves of different spatiotemporal scales; and (2) To shed new insights into the climatological features of tropical waves, such as life cycles, their interactions with other tropical phenomena, and their dynamical implications. To accomplish the first goal, we introduce the multi-dimensional ensemble mode decomposition (MEEMD) method to decompose different meteorological variables. This method is combined with our newly developed optimization methods based on tropical wave theory in this study to form a dynamics based tropical wave diagnosis package. The capability of the new package is validated using both synthetic data and observational data. It is demonstrated that our package has high capability of separating tropical waves of different spatiotemporal scales as well as of different types. With the readiness of the above package, we systematically analyzed characteristic of tropical waves of different types, with emphases being placed on the spatiotemporal structures and their life cycle. It is revealed that all types of tropical waves have significantly different climatological characteristics, from wavenumbers and wave frequencies to their propagating properties. It is revealed that that upper and lower tropospheric tropical waves have distinguishable dynamic characteristics, too different for researchers to adopt a first baroclinic mode structure in the vertical to understand the origin and destiny of various tropical waves. We also quantify the modulation characteristics of high frequency tropical waves by intraseasonal oscillations. / 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 2017. / October 31, 2017. / convectively coupled, locality, tropical waves / Includes bibliographical references. / Zhaohua Wu, Professor Directing Dissertation; Yiyuan She, University Representative; Mark A. Bourassa, Committee Member; Ming Cai, Committee Member; Vasu Misra, Committee Member.