Balloon-borne cryogenic air sampler experiment for the study of atmospheric trace gases

Abstract

A balloon-borne cryogenic air sampler for collecting tropospheric and lower stratospheric ambient air has been developed indigenously. It has 16 stainless steel sampling tubes, each having a motor driven metal bellow valve, operated by telecommand. A balloon flight carrying, this air sampler was made on 16 April 1994 from the TIFR (Tata Institute of Fundamental Research) balloon launch facility, Hyderabad (17.5°N). Fifteen air samples were collected during the ascent and slow valve controlled descent of the balloon in the 8-37 km altitude region. These collected samples were analysed at Physical Research Laboratory (PRL), Ahmedabad, using gas chromatographic techniques for many of the trace source gases. The vertical distribution profiles of N₂O, CFC-12, and Halon-1211 thus obtained were compared with the measurements made earlier. The vertical distribution profiles of N₂O and CFC-12 show discernible features in the stratosphere compared to earlier measurements during 1987 and 1990 from Hyderabad. Tropospheric growth rate of gases like CFC-12 and Halon-1211 during the period 1990-94 appear to be lower than those measured during 1987-90.