Publication Date

2018-05-01

Availability

Open access

Embargo Period

2018-05-01

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Meteorology and Physical Oceanography (Marine)

Date of Defense

2018-03-28

First Committee Member

Lynn K. Shay

Second Committee Member

William E. Johns

Third Committee Member

Benjamin Jaimes

Fourth Committee Member

Arthur Mariano

Fifth Committee Member

Ruoying He

Abstract

The unique characteristics of the Caribbean Sea’s upper ocean are investigated to understand its influence on air-sea processes during tropical cyclones (TC). The Caribbean Sea upper ocean is complex, containing large warm core eddies (WCE) which propagate through the basin and the Amazon-Orinoco River plume, which induces a vertical salinity gradient. Both of these features have been shown in literature in other ocean basins to influence TC intensity. Thus, it is imperative to understand how these features influence Caribbean Sea TCs. To pursue the main research goal, first, the upper ocean structure of a large anticyclonic eddy and its surrounding waters were measured during an aircraft oceanographic survey over the eastern Caribbean Sea. Observations from the survey are the first that identify a barrier layer within a warm core eddy (WCE) in the Caribbean Sea. This vertical salinity feature increases upper ocean stability in addition to reducing the efficacy of wind-induced mixing. Moreover, the isothermal structure within the surveyed WCE is similar to Gulf of Mexico WCEs which are known to provide a favorable ocean environment to passing TCs. Air-sea fluxes during Caribbean Sea TC events were estimated and compared with respect to upper ocean thermal and haline variability to assess how ocean variability, specifically upper ocean salinity, plays a role in enhancing and sustaining air-sea flux. Results highlight how salinity stratification within the Amazon-Orinoco River plume reduces entrainment heat flux within the ocean mixed layer, reducing SST cooling, and sustaining air-sea fluxes, similar to that over the WCE features. Finally, the impact of upper ocean thermal and haline structure is investigated numerically using one-dimensional (1D) mixed layer models and the Weather Research and Forecasting (WRF) model. Idealized temperature and salinity profiles are used with several 1D models to understand how vertical temperature and salinity gradients play a role in sea surface temperature (SST) response during TCs. The WRF model is used to investigate the how differing ocean representations and the influence of salinity impact TC air-sea fluxes, intensity, and track during Hurricane Ivan (2004) in the Caribbean Sea. All simulations highlight how the inclusion of salinity becomes important in SST response when TCs encounter shallow isothermal layers, such as in river plumes, and how accurate representation of salinity in WRF is needed to replicate SST cooling, air-sea fluxes, and TC track and intensity. Overall, it is found that Caribbean Sea upper ocean provides a favorable ocean environment for TC intensification and that salinity stratification within the Amazon-Orinoco River plume in the Caribbean Sea increases upper ocean stability, delays rapid deepening of the ocean mixed layer, reduces SST cooling, and sustains air-sea fluxes during TC passage.

Keywords

Caribbean Sea; Air-Sea Interaction; Tropical Cyclones; Upper Ocean Dynamics; Barrier Layer

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