Role of upper ocean parameters in the genesis, intensification and tracks of cyclones over the Bay of Bengal

Abstract

It is well known that the frequency of cyclones is about four times higher over the Bay of Bengal when compared with the Arabian Sea. Most of the severe cyclones during pre-monsoon (April and May) and post-monsoon (October and November) seasons hit the east coast of India, causing colossal loss of life and damage to property. In this study an attempt has been made to show the importance of the upper ocean parameters known as the upper ocean heat content (UOHC) and the UOHC with stratification (UOHCS). The UOHC has been computed considering the stratification parameter (S) for the first time. Most of the severe cyclones are forming over the UOHC range between 40–80 kj/cm2 in the Bay of Bengal. The UOHCS was high ranging from 50–400 kj/cm2 compared to the Pacific Ocean, which is due to high stratification (S ∼2–4). Climatology of cyclone tracks and the UOHCS and in situ observation from Argo suggest that most of the tracks in the pre- and post-monsoon seasons are influenced by the high UOHCS (>120 kj/cm2). UOHC and S are the dominant factors during the pre- and post-monsoon seasons, respectively. In addition to the atmospheric parameters from ocean-side, UOHC and stratification appear to be the best parameters to examine the intensification and movement of the cyclones during the pre- and post-monsoon seasons over the Bay of Bengal.