Vertical distribution of chlorofluoromethanes in the upper troposphere and lower stratosphere

Vertical profiles of CCl₄, CFCl₃, and CF₂Cl₂ mixing ratios in the upper troposphere and lower stratosphere have been measured on four flights with chartered aircraft, type HS 125. The flights were carried out in November and December 1976 over Europe at latitudes between 50 and 60°N. At least eight air samples were taken during each ascent and descent of the aircraft at altitudes between 7 and 12.5 km. The samples were analysed in the laboratory using gaschromatographic procedures. The results indicate a decrease of the CCl₄, CFCl₃, and CF₂Cl₂ mixing ratios above the tropopause. The observed average gradients in the stratosphere are 14 pptv/km for CCl₄, 12 pptv/km for CFCl₃ and 27.8 pptv/km for CF₂Cl₂. With exception of CFCl₃ these gradients are higher than those predicted by model calculations. Apparently, further sink mechanisms for CCl₄ and CF₂Cl₂ exist in the lower stratosphere not yet included in the models.