Surface fluxes from satellite winds: Modeling air-sea flux enhancement from spatial and temporal observations

Scatterometer and buoy observations are collocated at different locations spanning a range of climatic regimes in order to (1) develop a spatiotemporal conversion method that allows synergistic use of satellite and in situ data to estimate flux enhancement due to unresolved wind variability, and (2) formulate a resolution-dependent velocity-scale term to incorporate in bulk formulas. The scales found in point 1 above rarely agree with advective scales and are considered as the proper averaging scales for calibration of satellite spatially averaged observations against temporal averages. The flux underestimation due to unresolved directional variability in NASA scatterometer (NSCAT) data varies by region, wind regime, and local conditions. It is most important in the Atlantic due to larger subgrid Variability and favorable thermodynamic conditions. It is slightly less important in the Gulf of Mexico locations that experience favorable thermodynamic conditions and more light wind cases but smaller subgrid variability for a given light wind value. Even when small, the flux underestimation of the 50-km NSCAT data represents a systematic error for which a simple correction exists. A general velocity-scale formulation for typical model scales is developed based on NSCAT observations. It is consistent with studies that used aircraft flux observations. For typical general circulation model scales of 250 km, the associated heat flux enhancement is as much as 10, 23, and 40 W m(-2) for strong, midrange, and light wind regimes, respectively. By inserting a simple velocity-scale formulation into the bulk aerodynamic relationship, a modeler can effectively account for most of the flux underestimation.