Changes in wind direction in association with the phases of the El Niño-Southern Oscillation (ENSO) are identified over the Southeast region of the United States during the winter season (December-February). Wind roses, which depict the percentage of time the wind comes from each direction and can graphically identify the prevailing wind, are computed according to a 12-point compass for 24 stations in the region. Unfolding the wind rose into a 12-bin histogram visually demonstrates the peak frequencies in wind direction during each of the three (warm, cold and neutral) phases of ENSO. Normalized values represent the number of occurrences (counts) per month per ENSO phase, and comparison using percent changes illustrates the differences between phases. Based on similarities in wind direction characteristics, regional topography and results from a formal statistical test, stations are grouped into five geographic regions, with a representative station used to describe conditions in that region. Locations in South Florida show significant differences in the frequencies in wind direction from easterly directions during the cold phase and northerly directions during the warm phase. North Florida stations display cold phase southerly directions, and westerly and northerly directions during the warm phase, both of which are significant for much of the winter. Coastal Atlantic stations reveal winds from westerly directions for both phases. The Piedmont region demonstrates large variability in wind direction due to the influence from the Appalachian Mountains, but generally identifies warm phase and cold phase winds with more zonal influences rather than just from south or north. The Mountainous region also indicates southerly cold phase winds and northerly warm phase winds, but also reveals less of an influence from ENSO or significantly different distributions. Comparisons between observed patterns and those obtained using the NCEP/NCAR Reanalysis data reveal how the model-derived observations resolve the ENSO influence on surface wind direction at selected locations. Overall, resolution of the strength of the signals is not achieved, though the depiction of the general pattern is fair at two of the three locations. Connections between the synoptic flow and surface wind direction are examined via relationships to the storm track associated with the 250 hPa jet stream and sea level pressure patterns during each extreme ENSO phase. Discussion of reasons the NCEP reanalysis illustrates surface wind direction patterns different from those derived from observations is included. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester, 2006. / April 21, 2006. / Wind Roses, Southeast United States, Surface Wind Direction, ENSO, NCEP/NCAR Reanalysis / Includes bibliographical references. / James J. O'Brien, Professor Directing Thesis; Fei-Fei Jin, Committee Member; Carol Anne Clayson, Committee Member.

This dissertation consists of two complementary major sections. The first is an examination of summertime cyclone transport processes during NASA's Intercontinental Chemical Transport Experiment (INTEX-A) field campaign during Summer 2004. Warm conveyor belts (WCBs) are important mechanisms for transporting pollution during the cool season. These airstreams distribute surface emissions throughout the troposphere, playing a major role in the long range transport of chemical species. Previous efforts to understand the lofting of WCBs have not investigated the relative importance of vertical forcing. In this study, we use fine resolution model-derived meteorological data, air parcel trajectories, flux calculations, and a diagnostic package for weather systems to perform a focused investigation of WCBs during the warm season INTEX-A period. Lifting and transport mechanisms during INTEX-A are compared to a well documented cool season WCB case in the literature. Results show that weak, mid-latitude cyclones are capable of producing vertical transport as great or greater than much stronger cyclones. An analysis of forcing terms contributing to vertical motion reveals that the Laplacian of latent heat release is the primary contributor to vertical motion during some cases of INTEX-A. The latent heating term is found to be greatest in areas of deep convection. This convection allows weak cyclones to produce WCB-like transport. WCB pathways are similar for the cases studied. In each example, air which originates far south of the low in the warm sector, ascends to the north, and joins the upper-level westerly flow northeast of the low center. Although the transport pathways are similar, the forcing mechanism and location of maximum vertical transport are found to exhibit strong case-to-case variability. When cyclone scale dynamics are relatively weak, widespread deep convection, especially south of the cyclone's center, is necessary to produce transport resembling a WCB. The second major component of the research is an investigation of warm season carbon monoxide (CO) transport episodes during INTEX-A using synthetic data to simulate CO retrievals from MOPITT's gas correlation radiometers. This was done as if MOPITT was in geosynchronous orbit, providing simultaneous views of CO rather than the much sparser view currently provided by operational MOPITT aboard the polar orbiting Terra satellite. Pollution and its transport are global problems that require space-derived measurements for diagnosis and research. Since CO has a median lifetime of approximately two months, it is a good tracer of tropospheric circulations. This study determines the extent to which space-based MOPITT retrievals describe CO during several meteorological scenarios. Our procedure creates synthetic MOPITT retrievals using CO output from the Sulfur Transport Eulerian Model (STEM) regional scale chemical transport model. That is, STEM-derived CO vertical profiles are imported into a radiative transfer code. The calculated radiation spectra then are input to the MOPITT CO retrieval algorithm to create a synthetic version of MOPITT CO. MOPITT is assumed to be in geostationary orbit, and the effects of clouds are not considered. Simulated imagery is shown to be a valuable tool for understanding the capabilities of current sensors and the potential for new sensors to be placed on different platforms. This type of study would not have been possible using operational retrievals. We examine three phenomena observed during INTEX-A: Alaskan fires, urban plumes, and a warm conveyor belt. The evolution of thick, broad STEM CO patterns in the mid-troposphere is well represented by the synthetic MOPITT CO retrievals. Due to the MOPITT retrievals having coarse vertical resolution, as well as being constrained by a priori information, differences in the magnitudes of STEM and MOPITT CO were often seen. Neglecting differences in magnitude, MOPITT is shown to be useful at describing CO during several meteorological scenarios, specifically in the upper troposphere. / A Dissertation submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2006. / October 12, 2006. / Warm Conveyor Belts, Carbon Monoxide, Remote Sensing, Warm Season Transport / Includes bibliographical references. / Henry Fuelberg, Professor Directing Dissertation; Ruby Krishnamurti, Outside Committee Member; Jon Ahlquist, Committee Member; Guosheng Liu, Committee Member; Paul Ruscher, Committee Member.

This study diagnoses the anomaly fields of the Southern Hemispheric stratosphere in the period from 1 January 2006 to 28 February 2007 and examines the forecasting skill of the NCEP GFS model for the Southern Hemisphere (SH) during this period. Observational and model forecast data were converted into anomaly field data in a semi-Lagrangian θ-PVLAT coordinate. The first two EOF modes of the potential vorticity (PV) anomaly in the θ-PVLAT coordinate constitute over 80% of the total variance. It was found that the SH stratospheric polar vortex is quite stable (with a period twice as long as its NH counterpart) and persistent, and that the NCEP GFS model forecasts exclusively dynamical processes such as the equatorial quasi-biennial oscillation (QBO) with extremely high success but possesses a cold bias in the troposphere and a warm bias in the stratosphere due to a lack of updated greenhouse gas information. Forecasting skill in the stratosphere was far higher than in the troposphere, and the second EOF modes possess higher forecast skill than the first. The good forecast skill in the stratosphere is due to the GFS's ability of capturing the slow poleward propagation of stratospheric thermal anomalies associated with the polar vortex oscillation. Overall forecast skill scores were high enough to indicate that the NCEP GFS model has great potential in stratospheric climate prediction, but the model needs timely evolving greenhouse gas information to improve further. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2008. / July 10, 2008. / Forecast, GFS, Mode, Annular, Southern, Stratosphere, Anomaly, EOF, NCEP, Oscillation, Polar, Vortex / Includes bibliographical references. / Ming Cai, Professor Directing Thesis; Philip Cunningham, Committee Member; Jon Ahlquist, Committee Member.

Idealized three-dimensional numerical simulations of deep moist convection in the presence of a symmetric midlevel vortex are analyzed to understand the evolution of system-scale vertical vorticity during the very early stages of tropical cyclogenesis. A localized thermal perturbation initiates deep convection and the modified initial vortex is allowed to evolve over the 48-hour simulation period. During this time, surface momentum, heat, and moisture fluxes are excluded to eliminate any possible intensification by CISK or WISHE processes. A spatial filter is applied to the model output to separate system-scale and convective-scale features in an objective manner, whereby the filter scale is determined by a spectral analysis of the vertical vorticity field. It is found that the primary contribution to system-scale vorticity intensification comes from the convergence of convective-scale cyclonic vorticity, supplied by vortical hot towers (VHTs). Vorticity tilting is found to play an insignificant role in this development. The spatial filter approach offers an alternative viewpoint to the traditional symmetry/asymmetry method, and distinctively emphasizes the highly asymmetric evolution of the system-scale vortex. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester, 2009. / August 17, 2009. / Hot Tower, Vorticity, Vortex, Filter, Cyclogenesis, Tropical Cyclone, Deep Convection, Mesoscale / Includes bibliographical references. / Robert Hart, Professor Directing Thesis; Paul Reasor, Committee Member; Paul Ruscher, Committee Member.

In past studies, El Niño-Southern Oscillation (ENSO) events have been linked to devastating weather extremes. Climate modeling of ENSO is often dependent on limited records of the pertinent physical variables, thus longer records of these variables is desirable. Noisy signals, such as monthly sea surface temperature, are good candidates for reproduction by several existing auto-regression techniques. Through auto-regression, influential principal component modes are broken down into a series of time points that are each dependent upon an optimal weighting of the surrounding points. Using these unique numerical relationships, a noisy signal can be reproduced by thus processing the leading modes and adding an artificial record of properly distributed noise. Statistical measures of important ENSO regions suggest that the nature of oceanic and atmospheric anomalous events is cyclic with respect to certain timescales; for example, the monthly timescale. To detect ENSO signals in the presence of a varying background noise field, the detection method should take into account the signal's strong phase-locking with this nested variation. Cyclostationary Emperical Orthogonal Functions (CSEOFs) are built upon the idea of nested cycles, unlike traditional EOFs, which incorporate a design that is better detailed for stationary processes. In this study, both EOF and CSEOF modes of a 50-year Pacific SST record are processed using an auto-regression technique, and several sets of artificial SST records are constructed. Appropriate statistical indices are applied to these artificial time series to ensure an acceptable consistency with the real record, and then artificial data is produced using the artificial time series. In all cases, the cyclostationary approach produces more realistic warm ENSO events with respect to timing, strength, and other traits than does the stationary approach. However, both methods produce only a fair representation of cold events, suggesting that further study is necessary for improvement of La Niña modeling. Shorter records of variables such as sea level height and Pacific wind stress anomalies can hinder the usefulness of auto-regression, owing to time point dependence on surrounding points. Using a regression technique to find an evolutionary consistency (i.e. physically consistent patterns) between one of these variables and a variable with a longer record (such as SST) can eliminate this problem. Once a regression relationship is found between two variables, the variable with the shorter record can be re-written to match the time evolution of the variable with the longer record. Here regression, both EOF and CSEOF, is performed on both sea surface temperature and sea level height (a 20-year record), and sea surface temperature and wind stress (a 39-year record). Once the regression relationships are found, artificial SST time series are incorporated in place of the original time series to produce several artificial 50-year SLH and wind stress data sets. 5 Pacific regions are chosen, and statistics and behavior of the artificial sets within these regions are compared to those of the original data. Once again the cyclostationary approach fares better than the stationary. In particular the EOF assumption of cross correlational symmetry fails to capture the direction-dependence of ENSO evolution, causing inconsistent ENSO behavior. This renders an EOF method insufficient for climate modeling and prediction, and implies that a better aim is to incorporate physical cyclic features via a cyclostationary method. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester, 2006. / November 7, 2006. / EOF, Autoregression, Wind Stress, Sea Level Height, SST, ENSO, Regression, CSEOF, Cyclostationary / Includes bibliographical references. / Mark A. Bourassa, Professor Directing Thesis; James J. O'Brien, Committee Member; T. N. Krishnamurti, Committee Member.

Climate shifts due to El Niño (warmer than normal ocean temperatures in the tropical Pacific Ocean) and La Niña (cooler than normal) are well known and used to predict seasonal temperature and precipitation trends up to a year in advance. These climate shifts are particularly strong in the Southeastern United States. During the winter and spring months, El Niño brings plentiful rainfall and cooler temperatures to Florida. Recent los Niños occurred in 1997-1998, one of the strongest on record, with another mild El Niño in 2002-2003. Conversely, La Niña is associated with warm and dry winter and spring seasons in Florida. Temperature and precipitation affect wildfire activity; interannual drivers of climate, like ENSO, have an influence on wildfire activity. Studies have shown a strong connection between wildfires in Florida and La Niña, with the more than double the average number of acres burned (O'Brien et al 2002; Jones et al. 1999). While this relationship is important and lends a degree of predictability to the relative activity of future wildfire seasons, human activities such as effective suppression, prescribed burns, and ignition can play an equally important role in wildfire risks. This study forecasts wildfire potential rather than actual burn statistics to avoid complications due to human interactions. This wildfire threat potential is based upon the Keetch-Byram Drought Index (KBDI). The KBDI is well suited as a seasonal forecast medium. It is based on daily temperature and rainfall measurements and responds to changing climate and weather conditions on time scales of days to months, and this index is high during dry warm weather patterns and low during wet cool patterns. The KBDI has been widely used in forestry in the Southeastern United States since its development in the 1970's, with foresters and firefighters have a good level of familiarity with the index and its applications. The KBDI is calculated daily and used as an index by wildfire managers. This study calculates wildfire potential using a statistical method known as bootstrapping. Many datasets contain approximately a half-century of data, and the limited dataset will introduce biases. Bootstrapping can remedy bias by simulating thousands of years of data, which retain the climatology for the past half-century. Bootstrapping preserves the mean but not the variance. By incorporating this method, this study will improve long-term forest fire risks that will become useful for those living or working near forests and assist in managing forests and wildfires. The Southeast Climate Consortium will also be issuing wildfire risk forecast for Florida and parts of Alabama and Georgia based on ENSO phase and the KBDI. Climate information and ENSO predictions are better served by incorporating them with known climate indices that are routinely used in the forestry sector. Wildfire managers and foresters operationally use the KBDI to monitor and predict wildfire activity (O'Brien et al. 2002). Meteorologists at the Florida Division of Forestry have demonstrated the validity of the KBDI as an indicator of potential wildfire activity in Florida (Long 2004). They showed that the value of the KBDI is not as important as the deviation from the monthly average. The wildfire risk forecast is based on the probabilities of KBDI anomalies and will present the probabilities associated with large deviations from the seasonal normal. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester, 2004. / October 28, 2004. / Forest Fire, El Nino, ENSO, Seasonal Forecast, KBDI, Keetch-Byram Drought Index, Bootstrapping / Includes bibliographical references. / James J. O'Brien, Professor Directing Thesis; Mark A. Bourassa, Committee Member; Kwang-Yul Kim, Committee Member.

In order to understand the physical mechanisms of the Australian summer monsoon,cyclostationary EOF analysis was conducted on the 23-year (1979-2002) Xie- Arkin pentad summer precipitation data and other key physical variables over the Australian monsoon region,including the tropical and southern Indian and Pacific Oceans. The first mode of precipitation represents the El Niño signal, the second mode is the seasonal cycle, the third mode describes thephase transition of ENSO between El Niño and La Niña, and the fourth and fifth modes represent separate components of the Madden-Julian oscillations. All five modes together explain about1/3 of the total variance of the pentad precipitation data. The physical mechanisms of the seasonal cycle, which explains the "mean" seasonal evolution of the Australian summermonsoon in the absence of other external physical mechanisms, are identified. The onset and termination mechanisms of the Australian summer monsoon are stronglyassociated with the surface temperature changes over the Australian continent and the resulting sea level pressure (SLP) changes. Almost a month prior to the monsoon onset, the surfacetemperature over northern Australia increases and consequently SLP decreases. This initiates an cyclonic circulation over Australia. The increased upward motion induced by the surfacewarming together with the anomalous cyclonic circulation results in the increased lower-level moisture convergence over the interior of Australia. This increases the amount of precipitationover northern Australia and eventually starts the monsoon. In conjunction with the anomalous cyclonic circulation, zonal wind anomalies over northern Australia change from easterly towesterly. During the termination stage, physical conditions over Australia are reversed. Variability of the Australian monsoon onset, termination, and strength was alsoinvestigated in terms of the first five major modes of monsoon precipitation found via CSEOF analysis. Whereas the seasonal cycle defines the fixed onset (~January 5 ± 5 days) and termination (~March 5 ± 5 days) dates, the presence of other modes alters these dates. The impact of each mode was investigated after each mode was added to or subtracted from the meanseasonal cycle, each having a strength corresponding to one standard deviation of its variability. It is shown that the contribution of each mode to the monsoon precipitation is geographicallycomplex and varies significantly throughout the monsoon period. One striking feature is that the impact of each mode is highly asymmetric with respect to its phase. The negative modes generally affect more significantly the onset, the termination, and the amount of monsoonprecipitation. Although each of the four modes make a unique and tangible contribution, the ENSO mode contributes most significantly to the overall mean and variance of the monsoonprecipitation variability. While the positive ENSO (El Niño) mode does not seriously alter the onset and termination times, the negative ENSO (La Niña) mode prolongs the duration of the Australian summer monsoon significantly. Although the contribution to the overall mean is small, the two MJO modes are the most dominating factor controlling the onset and terminationtimes of the Australian summer monsoon. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2006. / March 23, 2006. / Regression Analysis, Cyclostationary EOF Analysis, Seasonal Cycle / Includes bibliographical references. / Kwang-Yul Kim, Professor Directing Thesis; Robert Hart, Committee Member; Carol Anne Clayson, Committee Member.

As a continuation to the shortwave phase of the third Intercomparison of Radiation Codes in Climate Models (ICRCCM III) by Barker et al. (2003), this study establishes longwave benchmarks for inhomogeneous cloud fields and compares the performance of three approximate, one-dimensional (1D) radiation models. The benchmarks are calculated using a correlated-k three-dimensional Monte Carlo (3DMC) algorithm that is validated via comparisons to line-by-line calculations for simple atmospheres. The approximate methods include an independent pixel approximation (IPA) and two cloud-overlap schemes: maximum/random (MRO) and random (RO). The test cases are the same as those used in the shortwave ICRCCM III, and were generated from various cloud resolving models (CRMs). These cases represent a variety of inhomogeneous cloud types that are important radiative forcing mechanisms of general circulation models (GCMs). Domain-averaged fluxes and heating rates from these six "real cloud" atmospheres show that the IPA is consistently more accurate than the cloud-overlap models with respect to the benchmarks. For example, comparisons of model results for the ATEX case yield a maximum cloud layer heating rate error of -20 K/day from using cloud-overlap models, whereas the IPA error is only -2.5 K/day. These differences can be attributed to the 3D effects of cloud radiation, and indicate the need to refine longwave 1D climate radiation codes so that they compensate for unresolved clouds. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2008. / July 8, 2008. / Includes bibliographical references. / Robert G. Ellingson, Professor Directing Thesis; Ming Cai, Committee Member; Guosheng Liu, Committee Member.

A four-dimensional model was designed to assimilate ozone for a one-year period from January to December 1999. The model has 1 ° x 1 ° horizontal resolution and is 18 sigma levels in the vertical from 10 hPa to the Earth's surface. This Eulerian advection scheme uses total ozone from the Total Ozone Mapping Spectrometer (TOMS), and the NCAR/NCEP Reanalysis 3-dimensional wind field to calculate the evolving structure function and determine the vertical distribution of ozone over the model levels. Initially, ozone climatology is used to calculate the structure function. In this paper, the focus is on tropospheric ozone. We have analyzed the spatial and temporal variability of ozone at different atmospheric levels, and looked at a specific high ozone event occurring in March 1999, documented by the Indian Ocean Experiment (INDOEX) field study. For this reason, the region selected from 30N to 30S and 40E to 110E, is the primary focus in the study. Tropospheric NOx data from the global 3D chemistry-meteorology model MATCH-MPIC is used to examine the correlation of NOx with the tropospheric ozone in this study. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2004. / July 7, 2004. / INDOEX, Indian Ocean, Transport Chemistry, Ozone Precursors, Tropospheric Ozone / Includes bibliographical references. / T. N. Krishnamurti, Professor Directing Thesis; Ralph Dougherty, Outside Committee Member; Paul H. Ruscher, Committee Member; Guosheng Liu, Committee Member.

This study looks to examine trends in the annual cycle of Mesoscale Convective System (MCS) activity over Equatorial Africa and the Sahelian region to the north. Convective precipitation features such as these are a vital source of rainfall for this region. Improvements in the understanding and forecasting of these convective systems could lead to improvements in water resources throughout the region. 5 years of data (1998-2003, 2001 exempt) from the University of Utah Precipitation Feature Database are analyzed over Central Africa. Trends of MCC activity are examined to establish a seasonal cycle of activity and to identify signals that may identify wet/dry years. To do this, the overall region of study is split into 3 separate sub-regions based on location and precipitation schemes. Each of these regions is then investigated independently to determine trends and patterns in the seasonal cycle. Aside from number of systems, parameters such as the amount of rainfall per system and lightning data are also utilized to examine the seasonal cycles of activity. Strong trends emerge in the lightning data across the whole of central Africa, that link convection to topography across the region. As convection is initiated in the early afternoon hours, it is strongly correlated with regions of highlands across central Africa. From which point the cells intensify and concentrate over the lowland forests of the central African Basin. Orgainized convective features also favor certain highland features as well. Maxima in these features are noted in the Cameroon Highlands as well as the highlands to the west of the Great Rift Valley. Seasonal cycles in activity display a pattern that follows the maximum in solar insolation over each sub-region. A maximum in activity in each region is seen with this occurrence, including bi-modal trends in the regions closest to the equator. Also of note is a seemingly strong connection in the southern region to the size/strength of the southern branch of the African Easterly Jet. This relationship could prove to be a strong predictor of monthly rainfall for this region. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2007. / June 29, 2007. / TRMM, Precipitation Feature, MCS, MCC, African Easterly Jet, Seasonal Cycle / Includes bibliographical references. / Sharon E. Nicholson, Professor Directing Thesis; Robert E. Hart, Committee Member; Henry E. Fuelberg, Committee Member.