AIR-SEA INTERACTION OVER THE INDIAN-OCEAN DURING THE 2 CONTRASTING MONSOON YEARS 1987 AND 1988 STUDIED WITH SATELLITE DATA

The air-sea interaction processes over the tropical Indian Ocean regio n are studied using sea surface temperature data from the Advanced Ver y High Resolution Radiometer sensor onboard the NOAA series of satelli tes. The columnar water-vapour content, low-level atmospheric humidity , precipitation, wind speed, and back radiation from the Special Senso r Microwave Imager on board the U.S. Defense Meteorological Satellite Program are all examined for two contrasting monsoon years, namely 198 7 (deficit rainfall) and 1988 (excess rainfall). From these parameters the longwave radiative net flux at the sea surface and the ocean-air moisture flux are derived for further analysis of the air-sea interact ion in the Arabian Sea, the Bay of Bengal, the south China Sea and the southern Indian Ocean. An analysis of ten-day and monthly mean evapor ation rates over the Arabian Sea and Bay of Bengal shows that the evap oration was higher in these areas during the low rainfall year (1987) indicating little or no influence of this parameter on the ensuing mon soon activity over the Indian subcontinent. On the other hand, the eva poration in the southern Indian Ocean was higher during July and Septe mber 1988 when compared with the same months of 1987. The evaporation rate over the south Indian Ocean and the low-level cross-equatorial mo isture flux seem to play a major role on the ensuing monsoon activity over India while the evaporation over the Arabian Sea is less importan t. Since we have only analysed one deficit/excess monsoon cycle the re sults presented here are of preliminary nature.