Abstract
Samples of tropospheric and stratospheric air were collected on aircraft flights between October 4 and October 13, 1976. The region of the atmosphere surveyed was over the North American continent (approximately 18°N to 65°N latitude). Samples were obtained at heights ranging from about 3, 000ft. to 45, 000ft. Measurements of N2O, CF2Cl2, CFCl3, CH3CCl3, and CCl4 were made by GC/EC techniques, and of CH3Cl by GC/MS. The latitudinal and height profiles of these trace gases are reported in this paper. Calculations based on these measurements yield the following average tropospheric concentrations: [N2O]=(330±2) ppb v, [CF2Cl2]=(236±7) ppt v, [CFCl3]=(140±5) ppt v, [CH3CCl3]=(145±25) ppt v, and [CCl4]=(134±9) ppt v (where the ± values are the standard deviations). The N2O mixing ratio decreases only slightly in the lower stratosphere. CF2Cl2 and CFCl3 mixing ratios decrease by about 10% and 15% respectively, within 4km above the tropopause. CCl4 mixing ratio declines by about 50% within 4km above the tropopause. CH3CCl3 mixing ratios also show a sharp decline above the tropopause, similar to that of CCl4. CH3Cl on the other hand displays almost no change in mixing ratio between the free troposphere and the lower stratosphere.
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