Impact of SST on Tropical Cyclones in North Indian Ocean

Abstract

The impact of the cyclonic activity can be measured based on annual frequency, maximum sustained intensity, landfall, duration, surge height, accumulated cyclone energy and power dissipative index of cyclones. ‘Power dissipative index’ (PDI) is function of duration, frequency and maximum sustained intensity of cyclone (Emanuel 2005). PDI can represent the cyclonic threat better than storm frequency or intensity alone as PDI measures the cyclonic energy dissipation over the basin during a cyclonic event (Emanuel, 2005). PDI of the tropical cyclone over the North Atlantic Ocean basin was related to the climate change by correlating the PDI to sea surface temperature (SST) (Emanuel, 2005). In the present study, an attempt has been made to establish a correlation between the climate change and the cyclonic activities in the North Indian Ocean (NIO) basin. The PDI over the North Indian Ocean basin and individually over Arabian Sea and Bay of Bengal basins were calculated. The PDIs over these basins were correlated to SST obtained from the HadISST1 dataset for these basins. An increasing trend in the SST and tropical cyclone PDI was observed for the past 30 year time period in the North Atlantic Ocean basin by Emanuel (2005). A similar analysis of the cyclonic activity over the North Indian Ocean basin is carried out with the help of available best-tracks of the cyclones from Indian Meteorological Department (IMD) for a period of 23 years (1990-2013). The SST was calculated on temporal period as annual, pre-monsoon and post-monsoon period for study basins. Correlation coefficients for the SSTs over these temporal periods and the PDI of basins were obtained. It was concluded from the study that the SST was not sufficient to establish the changing climate for the cyclonic activities in NIO region for the future.