Zonal anomaly of sea surface temperature in equatorial Indian ocean and its possible effect upon monsoon Circulation

The paper calls attention to the existence of a well-defined zonal anomaly of sea surface temperature between the equatorial west and east Indian ocean. The effect of this anomaly on ocean-atmosphere exchange and low-level air circulation in the equatorial Indian ocean as well as the Arabian Sea are discussed. It is shown that phenomena like the equatorial westerlies, the double intertropical convergence zone, and the Somali Jet receive plausible explanation on the basis of the observed zonal anomaly of ocean temperature. The effect of upwelling and its eastward advance in the Arabian Sea during the southwest monsoon are discussed in detail and it is suggested that this effect through air-sea interaction may change the low-level air circulation over the Arabian sea in a manner which may affect the distribution of rainfall along the west coast of India as well as inland during August and also explain frequent occurrence of feeble low pressure troughs in the southeast Arabian Sea during this period. Vertical circulation cells attributable to the observed anomalies of ocean temperature and their possible effect upon monsoon circulation and rain are discussed.