A simple thermodynamic model for seasonal variation of monsoon rainfall

Abstract

Monsoons occur in the tropics on account of complex interaction between the continents, the ocean and the atmosphere and hence no simple model of the monsoon has been proposed so far. In this paper, a simple diagnostic model of the monsoon has been proposed based on the constraints imposed by energy and the moisture balance in a vertical column of the tropical atmosphere. The model demonstrates that the monthly mean rainfall depends upon evaporation, the net energy available in the atmosphere and the vertical stability of the atmosphere. The model simulates the seasonal variation of rainfall in India, Africa and South America remarkably well without explicitly invoking the concept of land-sea contrast in temperature. The model is useful to understand the impact of deforestation, greenhouse gases and aerosols on monsoon rainfall.