Surface winds in The Arabian Sea from MSMR — an Empirical approach

Abstract

Multi-channel Scanning Microwave Radiometer (MSMR) onboard 1RS P4 (Oceansat I) measured Brightness Temperature data of the different bands are found sensitive to the surface and the overlying atmosphere to different degrees. A judicious combination of multi-channel data can provide such oceanic/atmospheric parameters as surface wind speed, sea surface temperature, water vapour in the marine atmosphere, etc. This paper highlights results obtained in relation to surface wind speed. Co-location and concurrence of several ocean data buoys in the Arabian Sea with MSMR observations allowed empirical construction of D-matrix coefficients for surface wind speed. With both MSMR and the Arabian Sea buoys functioning for the period of one and a half year (June, 1999 to December, 2000) without interruptions provided a large database. All channels are found to exhibit moderate sensitivity to surface wind speed. MSMR data in the immediate vicinity (within 150 km) of the buoy locations and within a time window of one hour were used. A multi-channel linear equation for surface wind speed was subsequently derived. The equation was subjected to tests with independent data set for the period January - June 2001 over the Arabian Sea and found to be moderately accurate. The empirical equation is expected to be useful for regional applications over the Arabian Sea and over regions closer to west coasts, which might have been flagged out in the operational geophysical data stream. An interesting subset of data revealed the wind signatures of the May 2001 cyclone in the Arabian Sea.