Climatological Perspective of Tropical Cyclone Activity and Landfalling Trend in North Indian Ocean Region

Abstract

Tropical cyclones (TC) activity over North Indian Ocean (NIO) and the atmospheric and oceanic parameters responsible for the associated changes need to be analysed. The study is conducted by dividing the whole considered period into two parts i.e. pre-warming period (PWP) from 1880 to 1946 and 1947 onwards as current warming period (CWP) on the basis of sea surface temperature (SST) variation. During CWP, annual TC genesis trend over NIO and BOB is decreasing severely in contrast to that of AS. Probable reasons behind the decreasing trend of TC activity include large difference in air and atmospheric temperature anomaly, increased SST, decrease in surface level relative humidity (RH) and increased surface wind. However, their rate of intensification is found to be increasing. The increasing surface wind supports greater evaporation and result increasing mid-tropospheric RH encouraging the intensification during CWP. Odisha and Andhra Pradesh from India and among other rim countries, Bangladesh is the mostly affected regions during PWP. During CWP, besides Bangladesh, Indian states of Andhra Pradesh and Tamil Nadu are more vulnerable to landfalling BOB TCs. TCs formed over AS, landfall mostly over Gujrat and Arabian Peninsula. The percentage of landfalling TCs is found to have decreased over NIO. The direction of the wind has changed from SE-S to S-SW between the latitude 12oN-15oN during CWP. Near to 18oN, the wind direction is from SW-W in CWP, whereas during PWP, it was nearly SW over BOB. The wind pattern with increased magnitude near Arabian Peninsula between 15oN to 18oN are seen to be more steam lined, favouring more landfalls. The zonally varying SST from west to east over AS, causes TCs to suffer more eastward drift in contrast to BOB, where a meridional SST variation is observed. The location of genesis also modulates the track of landfalling TCs.