A COMPARATIVE-STUDY OF NEAR CONCURRENT DMSP-SSM I AND GEOSAT-ALTIMETER MEASUREMENTS OF SURFACE WINDS OVER THE INDIAN OCEANIC REGION/

In this paper, colocated, near simultaneous measurements of ocean surf ace wind speed near the Indian subcontinent from the Special Sensor Mi crowave/Imager (SSM/I) and Radar Altimeter onboard, respectively, DMSP and Geosat satellites are analysed. It is found that for about 84 per cent of cases, difference of two winds is within 3 ms(-1). However, w hen the colocated winds are averaged for entire period and over the gr id boxes of 2.5 degrees x 2.5 degrees, the correlation between the two winds appears to be very high. It is found that the absolute differen ce of the two winds has no apparent relation with the amount of water vapour and the amount of cloud liquid water present in the atmosphere. Further, the variations of absolute difference of two winds with SSM/ I winds, altimeter winds and significant wave height have indicated th at altimeter measurements of high wind speed are likely to be more ina ccurate compared to SSM/I measurements. The variation of bias and stan dard deviation of the difference of the two winds as measured in each 1 ms(-1) bin of altimeter wind indicated that the SSM/I wind and the A ltimeter wind are in good agreement within 12 ms(-1) of altimeter wind , and thus in this range any one can be used in the absence of another .