Estimation of Centre and Intensity of Tropical Cyclones over the North Indian Ocean Using Microwave Imageries - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 188

Estimation of Centre and Intensity of
Tropical Cyclones over the
North Indian Ocean Using
Microwave Imageries
Suman Goyal* and M. Mohapatra
India Meteorological Department, Mausam Bhavan
Lodi Road, New Delhi - 110003
*e-mail: [e-mail]
1. Introduction
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. During night, intensity
of the disturbance is not available which limits the operational application.
While the Dvorak method is the most popular technique for analyzing tropical
cyclones (TCs) through infrared and visible imagery, it has some known
weakness and biases, especially for weaker systems. These have been described
recently by Knaff et al. (2010).