When wind forces the ocean, a fraction of the momentum is transferred beneath the surface to generate currents and turbulent mixing of the water column. The variable of proportionality representing that fraction, traditionally modeled as a function of wind speed, is referred to as the drag coefficient. At low to moderate wind speeds (safely in the range 11-20 m/s), the relationship between wind speed and the drag coefficient is relatively well established as a monotonically increasing function. However, in very high winds, the nature of the air-sea boundary layer changes, and evidence suggests that the drag coefficient levels off or even decreases with wind speed. Most estimates of the drag coefficient at high wind speeds have been using atmospheric data sets. In this talk, we describe an inverse problem setup whereby sea surface temperature and/or surface currents are assimilated into an ocean only model, and the drag coefficient is adjusted to achieve the smallest model minus data misfit, for a small array of ocean measurements. At this point, we are using a twin experiment framework, and the data are extracted from a reference forward simulation of the ocean's response to a hurricane.
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