Investigating the Effect of Ocean Currents on the Surface Stress and Heat Fluxes over the Gulf of Mexico Using a Two-way Coupled Modeling System

Abstract:

A two-way coupled ocean-atmosphere modeling system is used to investigate the effects associated with air-sea interaction through the use of wind-current shear in the bulk formula. This study focuses on changes in the mean and the variability of the wind stress magnitude, the heat fluxes, the near surface temperature and the precipitation on meso-scale. The atmospheric and the ocean components of the coupled modeling system are the Weather Research and Forecasting Model (WRF) and the Regional Ocean Modeling System (ROMS) respectively. The ocean and the atmospheric models exchange data fields using the Model Coupling Toolkit (MCT). The ocean surface currents are passed to the atmospheric model for use in surface layer schemes to allow for the current to change the wind shear. The wind stress and heat fluxes computed by the WRF surface scheme are passed to the ocean model, which allows both models to use the same fluxes at the interface. The inclusion of the wind-current shear results in weaker surface stress over most of the Gulf of Mexico compared to the wind-alone estimate. Changes are also being found in the air-sea heat fluxes. The weekly averaged Latent Heat Flux (LHF) decreases by 1%~2% over most of the Gulf of Mexico by considering the currents effect, but localized LHF increases of ~10% are found in the Loop current. The sensible heat flux changes (> 5%) due to using the wind-current shear are found in the Loop Current as well as over the land. The air-sea heat fluxes associated with surface wind stress feedback onto the upper-ocean thermodynamics. The weekly mean SSTs increase over most of the Gulf of Mexico by using the wind-current shear, and significant increases (>0.2 K) are found next to the Loop Current and ocean eddies. However, the SSTs slightly decrease (~0.05 K) in the Loop Current.