Measurements of the effect of rain, snow and fogs on 8.6 mm radar echoes

A radar set has been used to investigate the propagation of 8.6 mm radiation through various types of weather. Measurements have been made of the attenuation caused by the precipitation particles and of the intensity of radiation scattered back. No attempt has been made to correlate the results obtained with drop-size distribution, but the results are plotted against precipitation rate. The attenuation caused by rain and the intensity of radiation scattered back by rain agreed well with theoretical predictions. The echo intensity from fogs was too low to be detected, but the attenuation of a corner-reflector echo was measured in several fogs of different visibilities. While the results were of the same order as those predicted by theory, there was some variation, especially for fogs causing low visibility. The attenuation caused by dry snow has not been measured, but moist snow produced attenuation two and half times greater than rain of similar precipitation rate. The echo intensity returned from the ¿radar bright band,¿ composed of melting snow, was 14¿19 dB more than the echo intensity from the dry snow above it, and 2¿8 dB more than the echo intensity from the rain below it.