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

Scatterometer and buoy observations are collocated at different locations s panning a range of climatic regimes in order to (1) develop a spatiotempora l conversion method that allows synergistic use of satellite and in situ da ta to estimate flux enhancement due to unresolved wind variability, and (2) formulate a resolution-dependent velocity-scale term to incorporate in bul k formulas. The scales found in point 1 above rarely agree with advective s cales and are considered as the proper averaging scales for calibration of satellite spatially averaged observations against temporal averages. The fl ux underestimation due to unresolved directional variability in NASA scatte rometer (NSCAT) data varies by region, wind regime, and local conditions. I t is most important in the Atlantic due to larger subgrid Variability and f avorable thermodynamic conditions. It is slightly less important in the Gul f of Mexico locations that experience favorable thermodynamic conditions an d more light wind cases but smaller subgrid variability for a given light w ind value. Even when small, the flux underestimation of the 50-km NSCAT dat a represents a systematic error for which a simple correction exists. A gen eral velocity-scale formulation for typical model scales is developed based on NSCAT observations. It is consistent with studies that used aircraft fl ux observations. For typical general circulation model scales of 250 km, th e 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 sim ple velocity-scale formulation into the bulk aerodynamic relationship, a mo deler can effectively account for most of the flux underestimation.