Stratospheric thermal emission and absorption near the 183.311 Gc/s (1.64 mm) rotational line of water-vapour

Abstract

Following the work of Barrett and Chung (1962), theoretical calculations have been made of the amount of thermal radiation in the vicinity of the pressure-broadened 1.64 mm H 2O line due to an assumed stratospheric water-vapour distribution. The results indicate that although the presence of water-vapour above 30 km would not be detectable from the ground at this wavelength, the expected noise temperature of an aerial at a height of 30 km is much larger than that to be expected at the 13.5 mm line (240°K as compared to 7°K for the atmospheric model assumed). For the absorption line, using the overhead sun as a source, the corresponding change in aerial temperature would be 4700°K at 1.64 mm as compared with 300°K at 13.5 mm. Thus a balloon-borne 1.64 mm radiometer could be used to investigate the amount of water-vapour in the 30–80 km region of the atmosphere.