Noaa tovs-derived moisture fields over the Arabian Sea and the Bay of Bengal and their association with the South-West monsoon

Abstract

Moisture fields derived from the Tiros-N Operational Vertical Sounder (TOVS) data onboard previous National Oceanic and Atmospheric Administration (NOAA) series of satellites have been used to study monthly moisture fields over the Arabian Sea and the Bay of Bengal for the years 1979-1981. It is observed that monthly averaged moisture fields over the Bay of Bengal are always more than those over the Arabian Sea at a given latitudinal belt. Further, the monthly mean moisture flux divergence has been calculated using monthly mean winds from ship observations over the same areas of the Arabian Sea and the Bay of Bengal. It is found that net moisture flux divergence over the Arabian Sea is consistently higher than that over the Bay of Bengal for the years, 1979, 1980, and 1981, which are deficient, and excess monsoon rainfall years in terms of departure from long-term climatological rainfall values. Moisture variability over the Arabian Sea and the Bay of Bengal on a monthly scale has also been studied for the months of June, July, and August for the years 1979-1981. A plot of the zonally averaged (at every 2° latitude) differential moisture signal (DMS) by latitude indicates the approximate position of the low-level westerly jet. The overall differential signal between zonally averaged moisture fields over the Arabian Sea and the Bay of Bengal has also been found to be an indicator of total Indian rainfall excluding orographically influenced regions, although more data is needed to firmly establish the relationship quantitatively.