Moisture distribution and water vapour flux over the Arabian Sea during an active and weak spell of southwest monsoon, 1973

Abstract

The radiosonde data collected during the Indo-Soviet Monsoon Experiment, 1973 have been utilised to study some aspects of the moisture distribution over the Arabian Sea during an active and weak spell of southwest monsoon in that year, The study shows that there is stratification of moisture field over the Arabian Sea during the weak monsoon except the equatorial region, particularly the eastern parts, During the active monsoon, the stratification is broken to the north of about 10°N and east of 60°E, resulting in the building up of a deep moist layer over this area from surface to 400 mb, The equatorial region is conspicuously dry in the middle layers -during the active spell. The moisture build up in the middle layers during both the spells is mainly brought about by large-scale vertical motion associated with synoptic scale disturbances rather than by advective processes. During active monsoon, large, scale upward motion is envisaged over north and east central Arabian Sea and subsidence near the equator.

The moisture flux computations show that there is a large net flux divergence over the Arabian Sea during the active monsoon and small net convergence during the weak monsoon.