Some Preliminary Studies of the Rapid Variations in the Index of Refraction of Atmospheric Air at Microwave Frequencies *

Abstract

The index of refraction of atmospheric air at microwave frequencies is being measured with equipment which compares the resonant frequency of a cavity through which air is being drawn with that of a closed reference cavity. The equipment is shown to give a measure of the rapid variations of air moisture since the changes in refractive index at these frequencies are primarily a function of air moisture. Preliminary comparisons of the simultaneously recorded fluctuations of microwave index of refraction and air temperature, both measured with equipment whose time constants are considerably smaller than those of the recording Esterline-Angus meters, demonstrate a marked correspondence between air temperature and moisture variations. The correspondence is shown qualitatively to be a function of height, insolation, and soil moisture. No immediate correspondence is noted between non-oriented wind speed fluctuations and either air temperature or refractive index.