After cyclones Amphan, Yass, Tauktae, and Mandous, which originated in the Bay of Bengal, it was cyclone Biparjoy of the Arabian Sea that battered parts of western India. Timely warning by the Indian Meteorological Department (IMD) and coast guard vehicles saved many fishermen from untold misery. The pre-cyclone watch, cyclone alert, and warning appear to have immensely helped in mitigating the cyclone damage. The issue here, however, is that the hitherto 'cool and calm' Arabian Sea, which paves the way for an average of one cyclone per year, is destined for more. In the last two decades, there has been a 52 percent rise in Arabian Sea cyclones. Rapid sea warming is the most pronounced factor contributing to the above trend.
In the Bay of Bengal, a constant source of fresh water from large rivers propels the sea to be constantly warm. A faster rate of warming, coupled with increased sea surface temperature and more moisture in the middle layers of the atmosphere, leads to quicker cyclones there. Also, not high enough hills mean less dissipation of winds to the land in the case of the Bay of Bengal, whereas high mountains direct winds towards the Arabian Peninsula so that the heat dissolves more effectively from the Arabian Sea. This phenomenon is not favourable for cyclones, which is why the world saw a lesser number of cyclones that originated in the Arabian Sea. But Biparjoy has served a warning to all stakeholders: constant high sea temperatures due to increased global warming consequent to high emissions of carbon dioxide are a persistent threat India can hardly afford to ignore.
Dr Ganapathi Bhat,
(gbhat13@gmail.com.)