Height of warm core in very severe cyclonic storms Phailin: INSAT-3D perspective

Abstract

Warm core is the characteristic that distinguishes tropical cyclones from its extra tropical counter parts, where the center of the cyclone is warmer than its environment. Two of the most common variables used to characterize the warm core are its strength and height. The strength is given by the magnitude of maximum perturbation temperature and the height is the level where the maximum perturbation temperature occurs. INSAT-3D, India's advanced weather satellite, is the first geostationary sounder over India and the surrounding Oceanic regions. INSAT-3D has 18 channel sounder with a resolution of 10 km to profile the atmospheric temperature and humidity. Brightness Temperatures (Tbs) from INSAT-3D sounder channels are used to analyze the warm core structure of Tropical cyclone Phailin (8–14 October 2013) over the North Indian Ocean. Only when the system becomes very severe cyclonic system, when the eye of the cyclone is clearer (fully cloud free), the sounder channel Tbs showed multiple maxima, with strong primary maximum in the middle level (600–500 mb) and the secondary maximum in the upper level (300–250 mb), unlike the conventional belief suggested warm core existence at 250 mb. Due to the high resolution of (10 km) INSAT-3D sounder channels, compared to the Micro wave channels (AMSU-A of 50 km resolution), the warm core structure below 10 km of the atmosphere is well resolved.