[Eoas-seminar] Seminar today
eoas-seminar at lists.fsu.edu
eoas-seminar at lists.fsu.edu
Thu Apr 12 09:52:19 EDT 2018
3:30 PM, Thursday, April 12, 2018
Dr. Johna Rudzin
Dept. of Ocean Sciences, Rosenstiel School of Marine and Atmospheric Science, University of Miami
An Assessment of the Caribbean Sea's Upper Ocean Influence on Air-Sea Interaction During Tropical Cyclone Passage
The unique characteristics of the Caribbean Sea’s upper ocean are investigated to understand its influence on air-sea processes during tropical cyclones (TC). Presently, no studies exist which investigate how upper ocean variability within the Caribbean Sea affects TC intensity change via air-sea interaction. This is a significant gap in knowledge given that large warm eddies continually propagate through the Caribbean Sea where TCs often attain major status and numerous studies have linked TC intensification to deep warm ocean mixed layers. Additionally, a few studies have highlighted how the “barrier layer”, an upper ocean salinity feature within the Caribbean Sea induced by the Amazon-Orinoco river plume, sustains SST and aids in TC intensification.
To address this gap, the three-dimensional temperature, salinity, and velocity structure of both the Caribbean Sea and a large anticyclonic eddy were measured via aircraft expandable instruments during an aircraft ocean survey over the eastern Caribbean Sea. The observations focus on the differences between the upper ocean in the eddy and the background flow and compare them with the nearby Gulf of Mexico. This includes analyses of the barrier layer, upper ocean stratification, temperature and salinity anomalies, and eddy origin. Subsequently, air-sea fluxes during Caribbean Sea TC events were estimated and compared with respect to upper ocean thermal and haline variability. Moisture and heat fluxes were compared to ocean heat content and sea surface temperature (SST) to understand if ocean variability plays a role in enhancing air-sea flux in relation to wind speed. Additionally, an isothermal layer heat budget was estimated in attempt to quantify the dominant upper ocean processes that affect air-sea exchanges during TCs. Finally, the impact of upper ocean thermal and haline structure are investigated numerically using one-dimensional mixed layer models and the Weather Research and Forecasting (WRF) model. For the one-dimensional experiments, idealized temperature and salinity profiles that are representative of Caribbean Sea ocean regimes are used to understand how thermal structure, the inclusion of salinity, and vertical salinity gradient play a role in the upper ocean response during TCs. The WRF model is used to investigate how different upper ocean representations and the influence of the vertical salinity gradient impact air-sea response, storm track and intensity for the case of Hurricane Ivan (2004) as the storm passed through the Caribbean Sea.
Overall, results suggest that the Caribbean Sea provides a favorable ocean environment for TCs such that (1) the upper ocean thermal structure is conducive for TC intensification and (2) salinity stratification within the Amazon-Orinoco River plume increases upper ocean stability, delays rapid deepening of the ocean mixed layer, reduces SST cooling, and increases air-sea fluxes comparable to warm eddy features.
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