On the relationship between snowfall intensity and attenuation of short millimeter waves

We measure the dependence of radio wave attenuation at 138, 247, and 340 GHz over a near-ground radio path of length 1025 m on the snowfall intensity R. We find that the relationship between the attenuation coefficient Γ at the frequency ν and the intensity R at distinct stages of a snowfall event is close to functional and is mainly nonlinear. This relationship can be fitted well by the function Γ(ν)=γ(ν)Rm(ν) in the observed range of snowfall intensities (R is not greater than 3 mm/h in terms of the water equivalent). The dependence of Γ on R at different frequencies may change drastically as the snowfall evolves from one stage to another. The data obtained at the mentioned frequencies during the entire observation time reveal that the statistical dependence of Γ on R is close to linear. The mean specific attenuation coefficients determined using this data set turned out to be equal to 0.82, 3.3, and 5.6 dB·km−1/(mm·h−1) at ν equal to 138, 247, and 340 GHz, respectively. The correlation coefficients turned out to be 0.89, 0.94, and 0.98, respectively. The obtained results are compared to the data obtained in other measurements, as well as to the theoretical calculations of the attenuation based on the coupled-dipole method.