Variability of Rain Attenuation in the 100-200 GHz Band Calculated from Experimental Drop Size Distributions

The attenuation produced by rain can be derived from experimental Drop Size Distributions (DSD) using physical models of scattering in particles (Mie and its Rayleigh approximation). As the frequency increases within the mm-wave bands, the specific attenuation becomes more dependent on the DSD, whereas attenuation is mainly determined by the rain rate R in lower frequency bands. As is well-known, Mie scattering becomes dominant in the mm-wave band instead of Rayleigh scattering, which is the main extinction mechanism in cm-wave frequencies. In this document, long-term DSD measurements from an optical Laser disdrometer available in Madrid, Spain, were used to estimate the specific attenuation produced by rain. A very long period of twelve years has been used for the analysis of rain attenuation in the 100-200 GHz band. The results compare well on average with the ITU-R specific attenuation model of Rec. P.838-3, but they show a significant variability.