Temperature Variations of Ground-Wave Signal Intensity at Standard Broadcast Frequencies

Variations of ground-wave signal intensity at standard broadcast frequencies appear to be more closely related to changes in tempetature than to any other single commonly observed meteorological measurement. Results presented here were obtained from an analysis of signal intensities and weather conditions over six paths between 30° and 45° north latitude. It was found that (1) the intensities tend to decrease markedly from their peak values when the temperature becomes high, (2) the amount of such decrease is approximately proportional to the path length in wavelengths, and (3) the temperature at which the peak value occurs varies with frequency. Sample curves of experimental data are presented. General relationships deduced from all paths are combined in a nomographic chart showing intensities relative to the peak value for various frequencies, path lengths, and temperatures.