Response of landfalling North Indian Ocean cyclonic disturbances to warming climate and associated environmental parameters

Abstract

The present study focuses on the landfalling activity of CDs formed over North Indian Ocean (NIO) and associated environmental parameters responsible for the same. The warming climate over NIO started from 1947 onwards and the period is designated as current warming period (CWP) and the earlier time frame (till 1946) as pre-warming period (PWP). The study reveals that Bangladesh, Andhra Pradesh and Tamil Nadu are more vulnerable to severe cyclones formed over BOB during the current warming climate. Whereas, for Arabian Sea (AS) region, Gujrat is prone to severe cyclones and Arabian Peninsula countries are vulnerable to cyclonic storms during the current warming climate. The climatological vertically integrated (mass-weighted) tropospheric wind pattern near TN coast has changed direction from westward during PWP to north-westward during CWP, favouring more landfall over AP and TN. Over the central part near the latitude 14°N, change in the magnitude has occurred with change in the direction of the winds from NW-N to NE. Because of the prevailing wind steering pattern, the systems that formed over the middle and southern BOB do not prefer to make landfall to WB and Odisha during CWP. Over AS, the wind is mostly directed towards GJ irrespective of the period considered, which favours more landfalling of CDs over the place. These winds are primarily part of mid-latitude westerly troughs. For BOB, the SST gradient is in meridional direction and hence most of the systems formed, suffer landfall over Indian coastal states and other rim countries face less landfalls. Over AS, SST gradient is zonally distributed and therefore, the eastward deflection of CDs is more observed, making the Indian state of GJ to be the most affected region. The study is expected to be helpful in the decision-making process in view of socio-economic impacts of landfalling CDs.