Atmospheric Circulation

Abstract

The South Asian Monsoon dominates the atmospheric circulation over the North Indian Ocean. It results from the annual, meridional migration of the Intertropical Convergence Zone (ITCZ), the global-scale tropical rain belt. During boreal summer, the ITCZ lies in the northern hemisphere, ensuring that atmospheric fields associated with the summer monsoon (e.g., winds and precipitation) have significantly higher magnitudes than they do during the rest of the year. The spatial and temporal structures of the ITCZ result from complex interactions among the atmosphere, orography, and ocean. One consequence of these interactions is that during summer the Bay of Bengal becomes the most active region of the global ITCZ. Superimposed on the climatological-mean annual cycle is variability at interannual and sub-annual time scales, with amplitudes as large as that of the annual cycle itself.