Seasonal cyclogenesis and the role of near-surface stratified layer in the Bay of Bengal

Abstract

The role of the near-surface stratified layer developed due to the spread of low salinity waters under the influence of freshwater influx on the cyclogenesis over the Bay of Bengal is addressed. The seasonal variation of the Effective Oceanic Layer for Cyclogenesis (EOLC) and the associated effective heat potential, the parameters that represent the thermo-haline regime of the near-surface stratified layer, is discussed in relation to the seasonal cyclogenesis over the Bay. It is found that the zones of cyclogenesis during May and November, representing the pre- and post-southwest monsoon seasons respectively, over the central Bay and the southeastern Bay fairly coincide with the zones of higher EOLC, possessing higher percentage of effective heat potential. The climatological mean-cyclone tracks closely align with the contours of higher EOLC and suggest that the surface flow associated with the EOLC guides the movement of the weather disturbance. Also, the percentage of effective heat potential increases in the direction of cyclone track. This study reveals that one should consider the EOLC parameter for identifying the zones of cyclogenesis and for better prediction of cyclone tracks in the Bay of Bengal.