Fluctuations in satellite-derived moisture fields over the Indian ocean and their possible linkage with the onset of the monsoon over India

Abstract

The TIROS operational vertical sounder (TOVS) and special sensor microwave imager (SSM/I) data for the period from April to September over four different years (1980, 1981, 1984 and 1988) onboard NOAA series and DMSP (Defence Meteorological Satellite Programme) satellites have been used to study the coherence of moisture fields in the box areas near the equator, the Arabian sea and the Bay of Bengal regions and the possibility of using the observed characteristics to relate with the onset of the Indian summer monsoon. A clear-cut trend reversal in moisture values has been observed over the box areas near th equator and at higher latitudes after the arrival of the monsoon. The temporal analysis of cross-over point between the boxes near the equator and the boxes at higher latitudes demonstrates the potential of observing the onset of the monsoon over India about a week earlier than the normal time, using weekly averaged moisture fluctuations in the box near the Somali coast and the box over the Arabian Sea. The comparison of moisture values among different boxes has also been made. The present analysis indicates the eastward increment in the moisture values.