The Effect of Rain on Satellite Sensor Estimates of Surface Roughness Conditions and on the Air-Sea Momentum Flux

Changes in the sea surface roughness from the combined effects of wind and rain, on scales of tens of kilometers, are being studied using the QuikSCAT scatterometer (NRCS) and simultaneous NEXRAD three-dimensional measurements of rain. The studies of air-sea interaction, related to surface fluxes. The results to be presented were acquired during a significant rain event in the Gulf of Mexico, to the east of Corpus Christi, and just south of Houston, TX in May 2005. Preliminary results in NRCS caused by rain, relative to that in nearby regions with negligible rain shows distinct characteristics. Three regions with different wind speeds (4-6, 6-8 and 8-10 m/s) show definitive variation of this total NRCS with respect to wind magnitude, satellite-relative wind direction, polarization and rainrate. Relative changes are stronger in the lower wind region for both polarizations, with H-pol providing a more definitive signature. At higher wind speeds (e.g. 10 m/s) the relative splash induced increases in NRCS are still significant, and show distinct differences between polarizations.