A study on the dynamics and energetics of the Indian summer monsoon

Abstract

The present study is carried out to study the mean circulation characteristics, the dynamics and energetics of the Indian summer monsoon through the analysis of kinetic energy, vorticity, angular momentum, heat and moisture budgets with the help of long-term mean (1979-88) analyzed data sets. The data base used in this study consists of the uninitialized analyses (12 Z) of the European Centre for Medium Range Weather Forecasts (ECMWF) for ten years (1979-88). In this set of ten years data base, the data for the 1979 summer is the part of the FGGE level IIIb analysis and the remaining data of nine summer seasons comprise the global analyses of the ECMWF. It is found that the summer monsoon circulation constitutes a major centre of low level convergence and upper level divergence over South East Asia. The circulation over the East African continent and the adjoining western Indian Ocean determines the strength of the ageostrophic motions in maintaining the lower tropospheric features of the monsoon. The entrance (exit) regions of the tropical easterly jet (tej) are characterized by production (destruction) of kinetic energy which is essential to maintain the outflow (inflow) prevailing at the respective locations of the TEJ. Futher, the study illustrates the role of moisture convergence and the release of diabatic heating to maintain the entire quasi-permanent monsoon circulation over South East Asia.