New sea surface salinity product in the tropical Indian Ocean estimated from Outgoing Longwave Radiation

The sea surface salinity (SSS) product as derived from space-borne satellite measurements of Outgoing Longwave Radiation (OLR), based on the algorithms developed by, is discussed for the tropical Indian Ocean (TIO) during the period 1995-2000. The monthly variation of derived SSS for the TIO is found to be comparable with the climatological (Word Ocean Atlas 98) monthly SSS map highlighting that the differential hydrological cycle over the northern Indian Ocean basins could be captured by the atmospheric convection parameter, the OLR. Larger variation in SSS is noticed in the Bay of Bengal during southwest monsoon and fall season. The derived lower SSS north of Australia and around Madagascar in July-October, 1996 represent the inflow of low salinity waters from the Pacific and the influence of local precipitation respectively. The deviation of derived SSS from that of WOA98 SSS varied between -0.5 and 1.5 psu for winter and spring seasons. Larger deviations (-4 to 4 psu), however, are noticed during fall season in the Bay of Bengal. This means that satellite derived OLR seems capable of providing SSS values, but appears overestimated in the Bay of Bengal suggesting the immense contribution from river run off. The seasonal variation of derived SSS from one year to the other is quite comparable (with a standard deviation of /spl plusmn/0.3 psu during 1995-2000) with the seasonal WOA98 SSS.