Attenuation of 8.6 and 3.2 mm radio waves by clouds

Measured attenuations associated with a variety of cloud conditions at wavelengths near 8.6 and 3.2 mm are reported. Two specific events, during which heavy rain clouds covered the sky, are examined and statistical data collected over a six-month period on a variety of cloud types are presented. The number of observations of some cloud types was not large and it was not possible to account for the gaseous attenuation with sufficient accuracy to get reliable values for the attenuation by the cloud droplets for a number of cloud types. The clouds causing the largest attenuations were the rain-bearing cumulonimbus ones. Of the nonrain clouds the two types for which the sample sizes are adequate and attenuations are sufficient for meaningful conclusions are stratocumulus and cumulus, their 35 GHz/95 GHz mean attenuation values being 0.18/0.61 dB and 0.12/0.34 dB, respectively.