The Abundance and Vertical Distribution of Methane in the Earth's Atmosphere.
Abstract
Theoretical expressions are derived for the equivalent widths of CY4 lines formed in the earth's atmosphere which take into account the variation of pressure and temperature with altitude in the atmosphere. When allowance is made for the curvature of the earth; information on the vertical distribution of CII 4 can be obtained from low-sun observations. The theoretical formulae have been employed for the analysis of observations of the t, 5 , and to-it lines in the 2 P3 band of CH4 at 1.666 in the solar spectrum. From observations made at Lake Angelus, Michigan, and Mount Wilson, California, the total numbers of CH4 molecules per square centimeter through the zenith are found to be 3.2 X t0 and 2.6 X 1019, respectively. The ratio of abundances is very nearly that which would be expected if the distribution of CH4 is world-wide and falls off exponentially with height at the same rate as the main body of the atmosphere. The observations are well represented by theoretical curves of growth for pure damping, with /4ir = 1.2 X t0 for Lake Angelus and /4ir = 1.0 X t0 for Mount Wilson. Within the experimental error the ratio of damping constants is equal to the ratio of ground-level pressures at the two stations, in agreement with theory.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1951
- DOI:
- 10.1086/145426
- Bibcode:
- 1951ApJ...113..567G