Thesis (M. S.)--Texas A&M University, 2006. / "Major Subject: Meteorology" Title from author supplied metadata (automated record created on Apr. 27, 2007.) Vita. Abstract. Includes bibliographical references.

Bibliography: pages 92-101. / The overall objective of the thesis is to investigate and interpret hydrological events occurring at the Cape Columbine upwelling site and the adjacent coastal waters, with special reference to St. Helena Bay. The first step in the study involves monitoring the meteorological occurrences which resulted in the prevailing hydrology and thus give a general background to the observed structure. It became necessary to establish two sub-systems in the area which can be distinguished on the basis of the time scales within which they operate. Generally speaking, outside St. Helena Bay the waters have a 3-5 day synoptic variability governed by meteorological conditions, but within the semi-closed system of the Bay itself a longer time span of around 25 days governs the processes in this separate but inextricably linked water body.

This thesis describes the atmospheric boundary layer above the Agulhas Current using shipboard meteorological measurements and rawinsonde ascents. The juxtaposition of the warm Agulhas Current and cool shelf waters is shown to have far-reaching effects on the overlying atmosphere. Air-sea fluxes of momentum, sensible and latent heat and resultant boundary layer characteristics demonstrate high horizontal inhomogeneity. The results suggest that this inhomogeneity is permanent. The spatial heat flux gradient is reflected in the overlying atmosphere by a transition in stability of the boundary layer and potential cumulus formation from the cool shelf to the warm current. For airflow perpendicular to the Agulhas Current an internal boundary layer was observed to develop at the inshore sea surface temperature front. Onshore-moving air accumulated a significant quantity of moisture during its trajectory over the current. When airflow is parallel to the current an atmospheric moisture front exists along the axis of the inshore sea surface temperature front. The mean thermodynamic structure of the atmosphere was investigated. An inversion capped the boundary layer whilst a second, higher-level subsidence inversion was found which acts to limit the vertical development of cumulus clouds and therefore the redistribution of heat and moisture above the boundary layer. The results presented in this thesis are useful in two ways. The Agulhas Current has frequently been linked to South African climate. This is the first dedicated study which quantifies and characterizes the atmospheric boundary layer in this region. Secondly, maritime airmasses are dramatically modified above the Agulhas Current. The resultant large horizontal inhomogeneity, its vertical extent and permanence suggest that its inclusion is vital to any successful climate model. Atmospheric general circulation models have been criticized for not taking into account regions of strong horizontal inhomogeneity. The results of this thesis support this argument and highlight the need for similar studies. Bibliography: pages 116-123.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Bibliography : leaves 88-89. / M.S.

Research investigating tornado outbreaks has primarily focused on events that have occurred during daylight hours. While nocturnal outbreaks tend to be less significant in terms of spatial extent and severity than daytime outbreaks, they still pose a serious threat to the general public, owing to the increased difficulty of conveying risk information during nighttime hours. Additionally, the meteorological conditions driving these events are less well established, increasing forecast difficulty. The goal of this research is to establish a climatology of purely nocturnal tornado outbreaks. Events that met the criteria set in this study for nocturnal outbreaks were analyzed spatially and temporally. A diagnostic mesoscale analysis was also performed on the environments present at the onset of the outbreaks. These analyses yielded new information regarding nocturnal tornado outbreaks, as well as results similar to findings of other research focused on nocturnal tornadoes.

An estimated 240 million people worldwide suffer from migraines. Migraines have disruptive capabilities, therefore, understanding the mechanisms that trigger them is crucial for effective prevention and treatment. Air mass types and migraine induced emergency department (ED) visits in select North Carolina counties were collected over a seven year period in order to determine a potential relationship. Barometric pressure changes associated with Transitional air masses were also analyzed for potential trends. Bootstrapping showed that Tropical air masses resulted in greater numbers of migraine ED patients, while Polar air masses led to fewer. Moist Polar air masses in particular were found to correspond with the fewest number of migraine ED patients. On Transitional air mass days, the numbers of migraine ED patients fell between those of Tropical air mass days and Polar air mass days. With regards to barometric pressure changes associated with Transitional air masses, no trends were found.

Cut-off low (COL) pressure systems are critical weather systems which can result in resulting various severe weather events on South Africa. COLs are often associated with surface cyclones which can enhance weather-related impacts on affected communities. This is shown by a case study of Cape Storm, a COL extension associated with explosive cyclogenesis that had dire effects on the Western Cape of South Africa. The stratospheric effects that determine a COLs extension to the surface and eventual impact on South Africa are studied from a potential vorticity (PV) perspective in terms of a case study, a climatology and an idealised framework. Deep COLs (which extend to the surface) are most frequent in the autumn months, are longer lasting, are more mobile and found most frequently in the higher latitudes. Stratospheric, high-PV intrusions that are associated with COLs are studied in detail with respect to a COLs extension. PV intrusions which extend closer to the surface more frequently result in surface cyclogenesis. This is independent on the size (or intensity) of the intrusion as PV intrusions which extend from higher tropopause heights tend to result in shallow COL development. COLs, have in the past, been viewed as upper-level systems that systematically extend to the surface. Composite analysis however shows that deep COLs associated with deep PV intrusions result in the simultaneous amplification of troughs throughout the troposphere, with the surface cyclone developing within a day of the COL. / Thesis (PhD (Meteorology))--Universty of Pretoria, 2021. / Geography, Geoinformatics and Meteorology / PhD (Meteorology) / Restricted

This study examines the relationship between lightning totals from the Geostationary Lightning Mapper (GLM) and convectively induced turbulence (CIT). Turbulence is a hazard that affects passengers and crew through injury, emphasizing the importance of turbulence forecasting. GLM and turbulence data collected from pilot reports (PIREPs) are analyzed to find the average distance where maximum lightning frequency occurred for warm season airmass thunderstorms from 2019-2021. On average, 410 km from the PIREP is where maximum lightning frequency occurred and varying flash rates showed that as the flash rate increases, there is a linear increase in distance away from the storm. Case studies were conducted to provide a spatial analysis of lightning relative to the PIREP, it is found that in four out of five cases, turbulence was being advected downwind of the convection. This research identifies approaches to use lightning data alongside other remote sensing products to aid in forecasting CIT.

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