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, categories 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. Coastal 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 the Bay of Bengal (BoB) TCs, which necessitates rigorous studies in the AS. The focus of this study is to improve our understanding of TC activity over the AS by analyzing the frequency of TCs and energy metrics of TC accumulated cyclone energy (ACE) and Power Dissipative Index (PDI) over the last 39 years. Energy metric analysis confirms the increasing intensity of TCs in the 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 Niño Southern Oscillation (ENSO) on TCs in the 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 from the 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.