Estimation of Centre and Intensity of Tropical Cyclones over the North Indian Ocean Using Microwave Imageries

Abstract

Early warning system of cyclonic disturbances (depressions and cyclones) involves various aspects including monitoring and prediction of their genesis, intensity and movement. Forecasters essentially require maximum surface wind and central pressure to estimate the intensity of cyclonic disturbances (CDs). Presently genesis, intensity of CDs over North Indian Ocean (NIO) is mainly monitored by Infrared (IR) and visible cloud imageries from geostationary satellites as surface observations over ocean are scanty (IMD, 2003). There is scarcity of direct observations from the surface and upper air over the NIO due to limited number of buoys and ships and absence of aircraft reconnaissance unlike over the North Atlantic Ocean and Northwest Pacific Ocean. Dvorak’s technique (Dvorak, 1975, 1984) is used to determine intensity of CDs using IR and visible cloud pattern taken by Kalpana and INSAT-3A satellites. The Satellite Division of the India Meteorological Department (IMD) is estimating centre positions and intensities of tropical cyclones by the Dvorak method, which uses infrared and visible imagery from Kalpana-1 geostationary meteorological satellite. The technique is subjective and imprecise as high degree of skill is required to recognize cloud patterns.