| A three-dimensional, regional, coupled atmosphere-ocean model with full physics is developed. The model performs well in simulating the cyclone that developed off the Carolina coast and traveled over the northwestern Atlantic Ocean on 19-20 January 1998. Model diagnosis is used to examine the air-sea heat and momentum exchanges and the responses in the upper ocean. Maximum heat flux appears over the Gulf Stream in the South Atlantic Bight (SAB), which results in rapid deepening of the cyclone off the Carolina coast. After the cyclone leaves the SAB, the heat flux maximum moves to over the Gulf Stream off Cape Hatteras and later northeast of Hatteras, which in turn enhances the wind locally. Oceanic response is closely related to the wind direction. Southerly and southwesterly winds tend to strengthen the Gulf Stream at the surface, whereas the northeasterly winds reduce the Gulf Stream and also generate the southwestward flows on the shelf. Running the atmospheric model alone with unchanged SST overestimates the oceanic effect on the cyclone, with the surface wind being about 5 to 10 per cent stronger. Large differences in the surface heat flux appear near the Gulf Stream mender troughs due to wind-driven lateral shifts of the stream, which in turn enhance the local northeasterly winds. |
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