17 - Use of the equation of continuity of water vapour for computation of average precipitation over peninsular India during the summer monsoon

Summary

Water vapour fluxes, computed across different walls of a triangular volume of peninsular India, bounded by Trivandrum, Bombay and Nagpur, were used to compute the net water vapour flux convergence on a monthly mean basis for the months June to September for the years 1967 to 1972. The precipitation rates over the region were computed by using the flux convergence values and the equation of continuity for water, and were then compared with the actual rainfall. The agreement between the computed precipitation and actual rainfall was found to be fairly close.

Introduction

Saha and Bavadekar (1973) computed the water vapour fluxes across different walls of a rectangular volume over the Arabian Sea during summer monsoon months of 1963 and 1964 and suggested that the major influx of water vapour into this rectangular volume was associated with the cross-equatorial flow (i.e. across the wall 42° E to 75° E) and the major outflow was across the section wall parallel to the west coast of India (0° to 26° N).

The onshore fluxes over the west coast of India were further studied by Saha and Bavadekar (1977) for the nine years 1964 to 1972 for the summer monsoon months and were correlated with the rainfall along the west coast of India and also over peninsular India bounded by Trivandrum, Bombay and Nagpur. The correlation coefficients were 0.87 for the west coast section (Trivandrum to Bombay) and 0.85 for the peninsular region, and these were statistically significant at the 1%; level.