VERTICAL DISTRIBUTION OF CHLOROFLUOROMETHANES IN 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. © 1978 Birkhäuser Verlag.