A Comparison of Wind Speed as Measured by the
Special Sensor Microwave Imager (SSM/I) and the Geosat Altimeter

J.A. Nystuen and J.E. Lilly

Department of Oceanography
Naval Postgraduate School
Monterey, California

A.K. Goroch

Naval, Oceanographic and Atmospheric Research Laboratory
Monterey, California

Abstract: Wind speed data have been routinely acquired at the Fleet Numerical Oceanography Center (FNOC) in near-real time from the Special Sensor Microwave/Imager (SSM/I), on board the Defense Meteorological Satellite Program (DMSP) satellite, and the radar altimeter on board the Geosat satellite. Both of these instruments use empirical algorithms which have been independently verified to measure wind speed in oceanic regions with an accuracy of +/-2m/s. A comparison is made of the SSM/I and altimeter wind speed measurement from four regions with different environmental conditions present. Areas of variable atmospheric water vapour content do not appear to reduce the high correlation between the SSM/I and altimeter measured wind speeds, suggesting that in the formulation of the regression algorithms adequate sensitivity to and variation of water vapour concentration allowed the algorithm to compensate for this environmental factor. Whereas areas with liquid cloud water or rain present showed SSM/I wind speed estimates higher than Geosat wind speed estimates, indicating further refinement of algorithms is required.

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