Satellite derived sea surface temperature distribution over the North Indian Ocean during the southwest monsoon season

Abstract

Sea surface temperatures derived from spectral radiance data in infra-red window region obtained from NOAA-5 and TIROS-N meteorological satellites for 3 years have been utilized to study their distribution over the north Indian Ocean during the southwest monsoon season, It is observed that in a normal monsoon season in the Arabian Sea, cold waters with sea surface temperature (SST) less than 28 deg. C start moving from equatorial region towards north or northeast by the early May, forming the southwest monsoon current. Simultaneously SST's off Somali coast start falling, marking the beginning of Somali current. These cold currents get well organized in June and continue through monsoon months till they disintegrate during September, Frequently, the axis of the cold current extends upto the west coast of India and shows forking over the Arabian Sea, similar to that observed by Findlater (1971) in the low level wind field. The lowest SST's in the season are about 22 deg. C, observed off Somali coast during July and August, On the other hand, the delayed onset of monsoon and subsequent weak monsoon activity over India in the year 1979 were associated with delay in the appearance of cold waters off Somali coast, and the delayed and weaker Somali current. Also, SST's off Somali coast were 2-3 deg. C higher than those prevailing in the normal monsoon seasons. In the Bay of Bengal SST's generally fall with the advance of monsoon, leaving a flat temperature distribution. Complex SST patterns, apparently dominated by transients, were observed during the monsoon season. Generally, warmer SST's prevailed over the north Bay with colder waters at lower latitudes.