Experimental Determination of Molecular Absorption Coefficients for Methane and Ammonia at Low Temperatures and Model Atmospheres for the Major Planets.
Abstract
The experimental determination of the absorption coefficients for methane and ammonia at low temperatures is presented. Experimental procedures are described and observations at moderate resolution, 0.25 - 1.0 cm('-1), are presented covering the spectral range of 600 - 12,000 cm('-1). The temperature was varied from a low of approximately 110(DEGREES)K to a high of 275(DEGREES)K and the broadening effects of hydrogen and helium were also studied over the temperature range. Representative spectra are presented for both the warm and cold temperatures. An empirical band model is developed for use with atmospheric modeling calculations. The calculation of several non-gray model atmospheres for each of the major planets is presented. The method of solution is discussed, including the techniques for calculating the opacity due to hydrogen, methane, ammonia, and the scattering by their ices. The deposition of solar energy in the upper atmosphere is found to be of major importance. The inclusion of the fundamental vibration band and the first overtone band of hydrogen contributes enough absorption to create a thermal inversion for each of the planets. The observed planetary effective temperatures and estimates of abundances of the gaseous constituents are used to restrict the range of parameters for the models. The brightness temperatures for the various models are calculated and compared to observations. The large abundances of methane and ammonia as determined by the absorption bands in the visible region of the spectrum appear to be an overestimate if the brightness temperatures in the thermal infrared are to match the observations. A more thorough study of scattering is recommended, especially in the visible region of the spectrum.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 1977
- Bibcode:
- 1977PhDT.......272S
- Keywords:
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- Physics: Atmospheric Science