Identifier

etd-09222015-180348

Degree

Master of Science (MS)

Department

Geography and Anthropology

Document Type

Thesis

Abstract

Tropical cyclones are some of the most devastating natural phenomena on the planet. While it has long been recognized that sea surface temperature is an important factor in the evolution of tropical cyclones, it is limited due to its two-dimensional nature. This research seeks to investigate the role of the three-dimensional oceanic thermal structure and translation speed (Uh) on the cyclogenesis and intensity fluctuations of these powerful storm systems. This investigation utilized two main data sets: (1) depth of the 26°C isotherm (D26) which indicates the depth (or volume) of the warm water layer, and (2) hourly-interpolated wind speed (U10) and translation speed (Uh). These two data sets were used to complete an along-track analysis of 23 named tropical systems during the 2005 North Atlantic basin hurricane season. A more detailed analysis of five of the season’s major storms (U10 > 50 m s-1; Dennis, Emily, Katrina, Rita, and Wilma) was undertaken to determine whether D26 and Uh for these major storms played a role in their attainment of major status.

Results suggest that the condition of the underlying three-dimensional oceanic thermal structure played a role in the cyclogenesis and intensity fluctuations. Uh was also found to be a likely factor in the intensification and weakening processes by affecting the amount of time a storm spent over the ocean. Oceanic mesoscale features such as warm- and cold-core eddies, coupled with Uh, are likely to influence storm intensity by providing either abundant or insufficient oceanic heat content. Specifically, warm-core eddies were found to be especially important for the rapid intensification of major storms. These storms were found to pass either in close proximity or directly over these eddies triggering intensification. The minimum D26 value for tropical storm cyclogenesis was found to be 23.5 m, and for hurricanes (category 1) it was 36.8 m. The surface area of the North Atlantic basin over which these minimum thicknesses of the surface warm layer occur was found to expand and then contract over the season (1 June – 30 November), reaching a peak in August and September. Linear regression models suggest that major storms, most notably category 5, appear to be influenced more by along-track D26 and Uh than weaker storms.

Date

2015

Document Availability at the Time of Submission

Student has submitted appropriate documentation to restrict access to LSU for 365 days after which the document will be released for worldwide access.

Committee Chair

Rohli, Robert V.

DOI

10.31390/gradschool_theses.1644

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