VERTICAL-DISTRIBUTION OF METHYL-BROMIDE OVER HYDERABAD, INDIA

A vertical distribution profile of methyl bromide (CH3Br), obtained fr om the samples collected at Hyderabad (17.5-degrees-N, 78.6-degrees-E) during a balloon flight conducted on 9 April 1990, is presented. Its mixing ratio varies from 8 pptv at 10 km to 0.5 pptv at 25 km altitude . It shows a sharp decrease above the tropopause. CH3Br is the major s ource of bromine radicals in the atmosphere in the 13 to 27 km height region. Halon 1211 (CF2BrCl) is the second major contributor of Br rad icals in the 10 to 25 km height region while Halon 1301 (CF3Br) is the major source of these radicals only above 25 km. The measured CH3Br p rofile agrees fairly well with the available results from 1-D and 2-D model computations.