SURFACE WIND SPEEDS OVER THE NORTH-SEA FROM SPECIAL SENSOR MICROWAVE IMAGER OBSERVATIONS

The Special Sensor Microwave/Imager (SSM/I) flying as part of the U.S. Defense Meteorological Satellite Program measures millimeter-wave radiation emerging from the Earth-atmosphere system at different directions of polarization that can be used to measure oceanic surface wind speed. The radiative transport within the radiometer channels is studied theoretically for a large set of oceanic/atmospheric situations with respect to surface wind speed variations. Statistical retrieval coefficients for the recoverage of surface wind speeds from the satellite measurements are then derived via regression analysis of the synthetic measurements simulate. The theoretically estimated accuracy for the globally valid passive wind speed retrieval is 1.4 m/s under conditions where no heavy rain hampers the surface-leaving radiation in reaching the satellite. The technique is validated with in situ wind fields over the North Sea being objectively analyzed from routine wind and pressure observations.