Date of Award

2020

Degree Type

Thesis

Degree Name

Master of Science in Oceanography

Specialization

Physical Oceanography

Department

Oceanography

First Advisor

Isaac Ginis

Abstract

It is well recognized that evaporation from the sea surface, primarily within a tropical cyclone (TC) core, provides heat energy required to maintain and intensify the storm. The sea surface temperature (SST) typically decreases within the storm core due to the mixing and upwelling processes in the upper ocean thereby limiting the storm intensity. This negative feedback to the TC intensity depends on the oceanic thermal conditions and salinity stratification ahead of the storm. Upper oceanic heat content (OHC) has become widely accepted as a measure of the ocean energy available to the TCs. Observational and modeling studies note that some TCs rapidly intensify while passing over warm core eddies (WCEs) because of their high OHC. TC intensification is also significantly affected by salinity-induced barrier layers (BLs) formed when a low-salinity is situated near the surface in the upper tropical oceans. When storms pass over the regions with BL, the increased stratification and stability within the layer reduce storm-induced vertical mixing and SST cooling. This causes an increase in enthalpy flux from the ocean to the atmosphere and, consequently, leads to TC intensification. In this study, we applied the Hurricane Weather Research and Forecast (HWRF) v.4.0 system coupled to the Message Passing Interface Princeton Ocean Model (MPIPOM). We conducted the idealized experiments in which the WCE is embedded into the U.S. Navy's Generalized Digital Environmental Model (GDEM) climatology with a specified size using a feature-based initialization procedure. Idealized vertical ocean profiles from Hlywiak and Nolan (2019) are selected to conduct the sensitivity of TC intensity to BL thickness. The goal of this study is to quantify the impact of WCEs and BLs in the upper ocean on TC’s self-induced cooling and subsequent feedback on TC intensity in three TCs in 2018, Jebi, Trami, and Kong-Rey.

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