THE ROLE OF MOIST BAROCLINIC INSTABILITY IN THE GROWTH AND STRUCTURE OF MONSOON DEPRESSIONS

The effect of latent heat of condensation on baroclinic instability pr ocess is studied using the model developed by Bonatti and Rao. This mo del includes the effect of latent heat of condensation as parameterize d by Mak, a zonal wind profile that varies linearly with pressure, and a constant lapse rate of -6 degrees C km(-1). The effect of dissipati ve terms and vertical variation of heating on baroclinic instability w ith positive and negative zonal wind shears is studied. Dissipative te rms and the type and intensity of heating change the selection of the most unstable wave. Viscosity and Newtonian cooling stabilize short wa ves. The characteristics of the most unstable wave obtained using a do uble maximum in the vertical distribution of heating and observed vert ical profiles of zonal wind and temperature representative of the summ er monsoon of India resemble those of observed monsoon depressions. Th e inclusion of dissipative effects makes the Green mode the most unsta ble wave.