Interdecadal variability of the pre-monsoon cyclone characteristics over the Bay of Bengal

Abstract

The low-pressure systems intensified to cyclones prior to the onset of the Indian summer monsoon season over the North Indian Ocean (NIO) are referred to as pre-monsoon season (PMS) cyclones. Climate change is amplifying the pre-monsoon cyclone landscape, fostering more frequent and intense storms with altered tracks, resulting in heightened risks for coastal communities and economies. This study investigates the interdecadal variations in tropical cyclone (TC) and key large-scale atmospheric parameters that influence the characteristics of cyclones, including track, frequency over the Bay of Bengal (BoB) during the pre-monsoon season from 60 years of data. The large-scale atmospheric parameters are analysed by calculating climatological anomalies. It is noted that the frequency of cyclones making landfall over the eastern Indian coastal landmass has increased in the recent decade compared to the past five decades. Compared to the past fifty years, the percentage frequency has increased in the recent ten years by 50%. At the low level, stronger easterlies are dominant and upper-level jet streams shift to lower latitudes, indicating that the path of cyclones has shifted from the north (N)-northeast (NE) to the northwest (NW), i.e., towards the east Indian coastal landmass, over the recent decade. In contrast to the previous five decades, an unusual low-pressure region has emerged over the NW India and Pakistan regions, creating a favourable path for cyclones moving towards the Indian region in recent decade. Cyclones have been more intense in the recent decade than they were in the previous five decades, according to the rise in low- and mid-level specific humidity (SPH) and temperature over the BoB.