On the role of the Atlantic Ocean in forcing tropic cyclones in the Arabian Sea

Abstract

This study examines the impacts of tropical South Atlantic sea surface temperature (SST) anomalies on the frequency of the Arabian Sea tropical cyclones (TCs) during the pre-monsoon season (May–June) using observations and climate model experiments. There is a statistically significant association between the Atlantic SST anomalies and the frequency of Arabian Sea TCs during May–June of 1979–2016 based on the observations. These results can be explained from a physical perspective through the classic Matsuno-Gill responses to the Atlantic SST forcing, leading to changes in vertical wind shear in the Arabian Sea. The reduced vertical wind shear related to the Atlantic SST warming is associated with anomalous upper-level westerlies and lower-level easterlies. The physical mechanisms identified in the observations are strongly supported by a suite of experiments with an atmospheric general circulation model. Overall, the experiments reproduce the observed Matsuno-Gill responses, which are responsible for changes in vertical wind shear, lending confidence to the strong impacts of the Atlantic SST anomalies on the frequency of pre-monsoon Arabian Sea TCs.