The vertical distribution of CH₄, N₂O, CFC-12 and CFC-11 in the middle atmosphere at mid-latitudes

Abstract

CH₄, N₂O, CFC-12 and CFC-11 data analysed from samples collected by means of cryogenic samplers from five balloon flights conducted during the 1982-1984 period, are presented. The vertical distributions of these gases show structures with dominant scale size of 16 ±2.5 km. The amplitude of the perturbation is larger for the species having steeper gradient. A comparison of the present results with the results of earlier measurements representing the period of 1977-1979 do not show any appreciable change in the mixing ratios of CH₄ and N₂O. However, an average tropospheric increase of (6.5±1)% per year is found for CFC-12 and CFC-11. This annual change in the mixing ratios of CFC-12 and CFC-11 is found to increase with height suggesting a time lag of about 6 years between the troposphere and the altitude region around 25 km. The average mixing ratios of CH₄ and N₂O are compared with the available satellite/spacelab data. This data set shows a satisfactory agreement with the present in situ measurements for the height region above 30 km.