Spectroscopic detection of CH₃CL in the upper troposphere and lower stratosphere

Absorptions due to the ν 1 band of CH 3 Cl have been identified for the first time in infrared solar absorption spectra of the upper troposphere and lower stratosphere. The spectral data were obtained with the ATMOS Fourier transform spectrometer onboard Spacelab 3 in May 1985 during four solar occultation events near latitudes of 30°N, 26°N, 25°N, and 49°S. Volume mixing ratio profiles of CH 3 Cl retrieved for the altitude range 12 to 23 km at these four latitudes do not show appreciable differences. Vertical mixing ratio distributions vary from 6 × 10 −10 at 12 km to 3 × 10 ‐10 at 23 km with an average uncertainty of about 25%. The retrieved mixing ratio does not decrease with altitude as rapidly as the data obtained by in situ techniques.