The Megha-Tropiques satellite developed under the joint Indo-French spaceborne climate mission, carries a six-channel millimetre-wave sounder SAPHIR (Sondeur Atmosphérique du Profil d’Humidité Intertropicale par Radiométrie) primarily meant for profiling the atmospheric humidity of the tropics. It has a high spatial resolution of 10km at Nadir with a swath of more than 1800km. The satellite operating at an altitude of 865km and an inclination of 20 degrees provides a high temporal frequency of 4-6 times in a day. These characteristics have facilitated studies on the genesis, development and tracking of tropical cyclones (TC) in the oceans around the Indian subcontinent. The recent Ashobaa cyclone that occurred in the Arabian Sea in 2015 was studied using the brightness temperature (TB) measured by the SAPHIR instrument. Dvorak’s technique of interpretation of satellite observation is used for determining TC intensity variation and eye location. A critical analysis on the variations in TB is obtained at its six wavelengths centred at about 183GHz. A comparative evaluation of the capabilities of all six channels of SAPHIR in measuring TC development is made to assess the best channel suitable for detection of TC and its intensity variations. It is found that channel 6 at 183+/-11.0GHz is relatively more sensitive to detect TC. Further, evaluation of capabilities of TB measured by SAPHIR made in our study confirms that orbit position of Megha-Tropiques satellite with more frequent sampling (4-6 times) is useful for supporting forecasting and now-casting of TC genesis to dissipation and its effects on land.

Megha-Tropiques, SAPHIR, brightness temperature, T-number, Ashobaa cyclone.