First time observation of latitudinal and vertical distribution of infra-red radiative flux using radiometer sonde over Indian Ocean during the INDOEX IFP-1999 and its comparison with other Indian stations

Abstract

Latitudinal distribution of radiative flux at different layers has been measured for the first time over the Indian Ocean from 15°N to 20°S during intensive field phase of INDOEX 1999. Simultaneously measurements have been made over three Indian ground stations, viz. Delhi, Pune and Trivandrum. The basic feature of radiative flux over the Indian Ocean, Delhi, Pune and Trivandrum is similar, i.e. the radiative flux increases with altitude and reaches a maximum value at 15 km and after that the increasing rate slows down. The most striking feature of this observation is the existence of radiative flux between 12 and 15 km of height near the equator (1.75°N, 62.98°E) which may be due to the combined effect of partly cloudy sky, presence of aerosol and ozone. In addition, at 13.3°N, 60.5°E a similar feature has been observed at a height of 14–15 km, which may be due to the increment of ozone by 25 Dobson Unit (D.U.) during the onward journey since no aerosol was observed. During the return journey, at 12°S, 60.4°E global warming is also observed at a height of 13–15 km, which may also be due to the combined effect of partly cloudy sky and the presence of aerosol and increment of ozone.