Seasonal variations of the field strength of ground waves

Seasonal variations in the intensity of ground radio waves traversing a path from Nice across the southern Alps at 1.554 kHz were studied from July 1973 to Jan. 1975. A minimum persisting from late May to late summer is reported. The intensity rises in early November to its high during winter and spring. Effects of soil humidity, ambient temperature, precipitation, and absorption by vegentation are considered. The effect of vegetative absorption on the path conductivity features resonance properties.