Variability of Rain Attenuation at Millimeter Waves due to Fluctuations of the Drop Size Distribution

Rain attenuation at millimeter waves is progressively more influenced by the Drop Size Distributions (DSD) as the frequency gets higher. This paper continues the work carried out on DSD data gathered in Madrid, Spain, over a long period of 15 years. Rain specific attenuation in the frequency range 30-300 GHz has been calculated using the DSD data and extinction cross-sections obtained for horizontal and vertical polarization through electromagnetic simulations. Previous results showed a significant variability around its reference value obtained from the rainfall rate. This variability was attributed to DSD fluctuations. This attribution is analyzed in the present study, that addresses three additional aspects: the relation between the variability parameter V and the rainfall rate; the average DSD obtained for different ranges of V; and finally the seasonal variations of the two previous ones. The paper includes some examples of application of the Gaussian model proposed for the parameter V.