Study of air-sea interaction processes over the Arabian Sea and the Bay of Bengal using satellite data

Abstract

The main objective of this work is to study the latitudinal and seasonal variation of latent beat fluxes (LHF) and associated atmospheric and oceanic parameters over the Arabian Sea (AS) and the Bay of Bengal (BB) for the year 1988.The atmospheric and oceanic parameters, like precipitable water (PW), ocean surface wind (WS), and cloud liquid water content, are derived from the Special Sensor Microwave/Imager (SSM/I), and SST is obtained from the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer. The latent heat fluxes have been estimated from the bulk aerodynamic formula using the above satellite-derived parameters. The surface-level humidity, an essential parameter required for computing LHF, has been estimated using Liu's global relation between monthly mean surface-level humidity and precipitable water. A comparison of these variables and the relation among them has also been made over the AS and the BB. A significant latitudinal variation is observed in LHF for most of the months over the AS and the BB, while other oceanic and atmospheric parameters are characterized by a strong latitudinal variation in nonmonsoon months. Seasonal variations in LHF are more significant at higher latitudes compared to lower latitudes over the AS and the BB. The effect of coastal upwelling near the Somali coast decreases LHF, while surface winds near the Indian coast during monsoon months increases LHF. A comparative study over the AS and the BB demonstrates higher PW and SST over the BB than over the AS. LHF is found to be greater over the AS than over the BB for nonmonsoon months. Correlation analysis indicates that LUF is found to be highly correlated with DQ (difference between the humidity at the surface and humidity near the surface) over the AS and weakly correlated over the BB during nonmonsoon months. Throughout the year, DQ is found to be a dominant factor for LHF over the AS. However, WS exercised better control over the BB in generating LHF. SST and PW are found to be highly correlated with each other over the AS (r = 0.87) and the BB (r = 0.75) for nonmonsoon months. The correlation becomes weakly negative over the AS (r = 0.15) and weak over the BB (r = 0.26) during monsoon months. Precipitable water is found to have a high correlation with WS over the AS (r = 0.72). This unique feature is revealed by SSM/I data and has not been reported earlier due to paucity of data over this region.