Measurements of N2O, CF2Cl2, CFCI3, CH3CCl3, CCl4, and CH3Cl in the troposphere and lower stratosphere over North Amrica.

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.