Identifier

etd-06152016-113323

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Upon comparison to typical neutral-ENSO conditions in the Northeast Pacific Ocean, the 2014 hurricane season has been identified as highly anomalous in both tropical cyclone frequency and intensity. This thesis seeks to investigate the influence of sea surface temperatures (SSTs) and upper ocean heat content (UOHC), defined as the excess of heat present above 26°C, upon the upper ocean thermal structure, mesoscale features, and anomalies that led to an active hurricane season in the Northeast Pacific. The 2012 Northeast Pacific hurricane season was selected as a ‘normal’ season to fully quantify the anomalous 2014 hurricane season. Data sets utilized in this work included optimally interpolated SSTs, UOHC, and the National Hurricane Center’s post-storm observation database. Oceanic variables were extracted nearest-pixel to the hurricane path and were scrutinized through the use of along-track time series analysis, gridded UOHC fields, and a complex scheme of linear regression models. In order to quantify intensity modulation throughout a hurricane, enthalpy flux was calculated along-track for the duration of the storm with atmospheric model data, as well as from in-situ dropsonde observations.

Results suggest that variable SSTs and UOHC were critical in tropical cyclone genesis, duration, and maximum intensity. A minimum requirement of 30 kJ cm-2 of UOHC was found at genesis for all storms. At least 7 of the major hurricanes interacted with a warm oceanic mesoscale feature either at genesis or along-track that induced rapid intensification periods, including one high-end Category-5 hurricane. Cool wake signatures from deep upwelling along-track were detected within gridded UOHC and were also found to be influential in changes of subsequent hurricane trajectories. Linear regressions suggested that storm-specific models, and not season-specific models, were optimal for estimating the influence of oceanic and environmental parameters within the intensification phase. Specifically, regressions for Hurricanes Emilia (2012) and Odile (2014) performed extremely well, indicating that a combination of oceanic parameters, storm position, and storm translation speed could explain 98% of along-track intensity variability. Along-track enthalpy fluxes peaked at 1234 W m-2 as the hurricane attained maximum intensity, while dropsonde-derived enthalpy emphasized stronger enthalpy fluxes within the northeast quadrants of the hurricane.

Date

2016

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Walker, Nan

DOI

10.31390/gradschool_theses.305

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