The possible detection of atmospheric water-vapour from a satellite by observations of the 13.5 mm and 1.64 mm H 2O lines

Abstract

Calculations of the atmospheric noise temperature spectra that would be expected to be observed from an Earth satellite at wavelengths near the 13.5 mm and 1.64 mm rotational lines of the water-vapour molecule, indicate that although both of these lines would be detectable at the satellite, very little useful information on the total vertical water-vapour content of the atmosphere could be obtained from the results. If ground measurements show a central enhancement of the spectra as predicted by Barrett and Chung (1962) for the case of an increasing stratospheric mixing-ratio, then this could be detected from a satellite, though even over the most favourable surface (water) the increase at 13.5 mm is only 5°K. The corresponding value at 1.64 mm is about 45°K and is independent of the type of surface, though it is very dependent on the temperature structure of the atmosphere.