Variability in Tropical Cyclone Activity Over Indian Seas in Changing Climate

Climate change due to warmer globe has become a prominent feature of the environment today and its effects on various atmospheric phenomena are becoming more apparent over time. Tropical cyclones (TCs) form an important component of climate phenomena and therefore it is necessary to gauge their changing patterns in warmer conditions for better understanding of their behavior and consequently better means of prediction. This study aims to analyze tropical cyclone activity in the North Indian Ocean (NIO) for the period 1979-2008. Generally tropical cyclones over this basin occur during pre- and post-monsoon season hence TC activity during above period is investigated by examining the length of cyclone season, storm frequency, storm days etc. in pre- and post-monsoon season. Also variation of different energy parameters such as Accumulated Cyclone Energy (ACE), Power Dissipation Index (PDI), etc. is studied. It is found that length of total cyclone season has an increasing trend, indicating expansion of cyclone season which is basically due to increase in pre-monsoon cyclone season length. Analysis of storm frequency over two Indian seas, Arabian Sea (AS) and Bay of Bengal (BOB) shows increase (decrease) especially of intense cyclones over AS (BOB). Energy parameters show significant increasing trend over the period.