From Glossary of Meteorology
For the centimeter wavelength band, clouds produce Rayleigh scattering. The attenuation is due largely to scattering, rather than absorption, for both ice and water clouds. The cloud attenuation for one-way transmission is
where M (g m-3) is the liquid water content, ρ (g cm-3) the density of water, λ the wavelength, and
, where m2 is the complex dielectric constant. The attenuation depends only on M, and in the range of wavelengths from 1 to 10 cm is approximately (1 to 100) × 10-2M for water clouds, and (2 to 20) × 10-2M for ice clouds.