Inter-Annual Variability of Air–Sea Fluxes over the Arabian Sea and Bay of Bengal; Evolution during a Monsoon Cycle and Impacts of Cyclones

Multi-year data sets on all the terms of the air-sea interactions, exchanges of heat, moisture, momentum, and other properties between the ocean and the atmosphere are now available from space born sensors at high spatial and temporal resolution. We examine the net energy and moisture fluxes and the separate terms constituting them: turbulent flux (latent heat), short and long wave radiative fluxes for several years (2003-2008) in the Northern Indian Ocean (Arabian Sea in the West and the Bay of Bengal in the East) documenting the Monsoon cycle. These data are available at 0.5 - 1 deg resolution, or better at daily time scales.

Analysis of the sea surface temperature and evaporation rate shows differences in the timing of the maxima in the two ocean basins with resulting effects on moisture transports to the continent. Procedures for calculating the moisture transport across the Indian coastlines are related to the warming of the upper ocean via air-sea fluxes and the consequent timing of precipitation during the monsoon onset. Disruption of these processes can occur due to passing Tropical Cyclones with consequences to the upper ocean and thus, the sea surface temperature and moisture (latent) heat flux. The associated cloudiness also modifies the radiative fluxes substantially. The recent plentitude of buoys, such as the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) in the Indian Ocean supports the analysis of these effects above and below the sea surface. We present a few cases highlighting the value of the remotely sensed data on evaporation from the Institut Francais de Recherche pour l’Exploitation de la Mer (IFREMER) product and the radiative data sets based on MODIS Moderate Resolution Imaging Spectroradiometer (MODIS) measurements from Terra and Aqua satellites. Motivation for the work is that remote monitoring of the large scale air-sea fluxes can lead to prediction of changes in the monsoonal flow of moisture and precipitation, once a complete and statistical analysis of a longer time-series becomes available.