Time-mean atmospheric circulation and diabatic heating Over the Arian sea during July

Abstract

Using the four-year (1963-66) mean July meteorological data of the International Indian  Ocean Expedition, the study computes vertical motion and deduces vertical circulation cells over the Arabian Sea and surrounding areas. The data are also used along with computed vertical motion to compute diabatic heating using the heat balance equation. The results suggest that diabatic heating constitutes the main forcing mechanism for atmospheric circulation in the Arabian Sea region, even though thermal advection makes an appreciable, contribution to the heat budget especially over the western Arabian Sea. thereby validating the approximate relationship. Q/Cp~-- where Q is the rate of diabatic heating, Cp is the specific heat of air at constant pressure, is the vertical p-velocity and a is the static stability parameter. The computed vertical circulation cells (Walker, Hadley and monsoon) have their sinking branches Over the western and northern parts of the sea where there is strong diabatic cooling and subsidence and rising branches over the eastern part of the sea where strong diabatic heating due to precipitation in the monsoon trough zone forces enhanced convection. Strong subsidence over the western part of the sea may well help maintain the observed boundary layer processes such as low-level temperature inversion and the Somali jet.