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IOVWST Meeting
Portland, Maine, USA, 2019

Observations and Modeling of Coupled Ocean-Atmosphere Interaction Over the California Current System

Presenting Author: Professor Dudley Chelton

A strong sea-surface temperature (SST) influence on surface winds and wind stress is well established from QuikSCAT observations of winds and AMSR microwave observations of SST over the SST fronts associated with the eastward extensions of westward boundary currents into the interior ocean. In combination with higher-resolution satellite infrared-based SST analyses, QuikSCAT wind observations reveal that this ocean-atmosphere interaction also occurs over eastern boundary currents where the scales of SST fronts are much smaller. In particular, the SST influence on the wind stress curl that drives open-ocean upwelling results in order-1 perturbations of the large-scale background wind stress curl field. On the atmosphere side, the SST influence on surface winds can be reproduced quite accurately with mesoscale models with a sufficiently accurate and high-resolution SST boundary condition and appropriate parameterization of vertical turbulent mixing. In particular, it will be shown that the SST-induced perturbations of the surface wind field are well represented over the California Current System by the U.S. Navy Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) model run in a 1-way coupled configuration in which SST forces the atmosphere. The feedback effects of the SST-induced perturbations of the wind stress and wind stress curl fields on the ocean are only beginning to be explored. It will be shown from a simple empirically based coupled model of an idealized eastern boundary current system that the feedback significantly alters the shallow equatorward surface flow and the nearshore deep poleward counterflow. These equatorward and poleward flows are analogous to the California Current and the California Undercurrent/Davidson Current. The coupling also modifies the mesoscale eddy field, preferentially weakening the cyclonic eddies because of their stronger SST signatures compared with anticyclonic eddies.

2019 International OVWST Meeting
May 29-31 in Portland, Maine, USA
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