Recent Trends in Tropical Cyclones Over the Arabian Sea and the Vulnerability of India’s West Coast

Abstract The IPCC’s sixth assessment report emphasizes the increase in the frequency of stronger Tropical Cyclones (TC, category 3–5) over the last four decades. The Northern Indian Ocean (NIO) exhibits identical trends. The Arabian Sea (AS) has become a breeding ground for TCs that have wreaked havoc on Oman, UAE, Iran, Muscat, and India’s west coast in recent years. The west coast of India is extremely vulnerable to TCs due to its unique coastal topography and population density. Most of the research on the North Indian Ocean is focused on Bay of Bengal (BoB) TCs, which necessitates rigorous studies in AS. The focus of this study is to improve our understanding of TC activity over AS by analysing the frequency of TCs and explaining observed higher intensity TCs in terms of Accumulated Cyclone Energy (ACE) and Power Dissipative Index (PDI) over the last 39 years. Energy metric analysis confirms the increasing intensity of TCs in AS. Annual ACE and PDI have been increasing in recent years primarily due to monsoon and post-monsoon TCs. While pre-monsoon TCs show a decreasing trend. The effect of El-Nino Southern Oscillation (ENSO) on TCs in AS is found to be negligible. The study also attempts to ascertain the vulnerability of western coastal districts to TCs using housing damage risk data Vulnerability Atlas of India. Ahmedabad and Vadodara in Gujarat, Thane and Mumbai Suburban in Maharashtra, Dakshin Kannada in Karnataka, and Malappuram, Ernakulam, and Thiruvananthapuram in Kerala are among the most vulnerable districts along India’s western coast.