The Influence Of North Indian Ocean Tropical Cyclone On Precipitation In China

Facing the situation of inadequate research in comparison of tropical cyclone datasets,regional differences in TC bimodal patterns in the North Indian Ocean and influence of North Indian Ocean tropical cyclones on China, a targeted study on these issues has been carried out using the Joint Typhoon Warning Center (JTWC) TC dataset and the India Meteorological Department (IMD) TC dataset. Results are as follows:time period of IMD dataset is much shorter and data recording time is irregular, while time period of JTWC dataset after the abrupt change in 1977 is much longer and data recording time is regular. Then, JTWC dataset of 1977-2012 is adopted in TC climatic characteristics analysis. During 1977-2012, the Bay of Bengal (BoB) TC frequency decreases, while the Arabian Sea (AS) TC frequency increases significantly. Meanwhile, seasonal variations of TC frequencies show bimodal pattern with two peaks in both BoB and AS, with obvious differences in bimodal peak time, intensity and strength configuration. It is revealed that vertical zonal wind shear and seasonal changes in relative vorticity might be the key factors affecting the bimodal patterns of TC activity in BoB and AS, respectively. Results obtained by precipitation separation showed:during 1977-2013,there are 41 North Indian Ocean tropical cyclones affecting 11 provinces and cities;All of affecting TCs origin from Bay of Bengal,most of which are at TS level.The main affecting month is May.The precipitation mechanism of tropical cyclones over the Bay of Bengal may be as follows:shear line, the confluence of warm and cold air and convergence line.