Control of Salinity Stratification on Recent Increase in Tropical Cyclone Intensification Rates over the Postmonsoon Bay of Bengal

Abstract:

This study explores the variability of tropical cyclone (TC) intensification rates (IRs) in the postmonsoon Bay of Bengal (BoB) for the satellite period of 1980-2015. It is found that both number of rapid intensification (RI) events and magnitude of IRs show a robust increase, with a northeastward shift of intensification events. Analyses show that the temporal variability of sea surface temperature dominates the IR variability during 1980-1997. However, the thick barrier layer in the northern BoB is considerably responsible for IR variability during 1998-2015, which significantly contributes the IR increase. Due to more intensification events occurring over the northeastern region in recent two decades, the thick barrier layer with strong salinity stratification in the northern BoB limits TC-induced sea surface cooling and in turn favors TC intensification. This study has an important implication that air-sea coupled climate model needs to realistically simulate upper ocean salinity variability on projecting TC intensity change over the BoB.