Statistical significance of specific rain attenuation dependence on geographic and climatic conditions

In satellite communications, among all atmospheric effects, rain has the biggest impact on signal transmission, causing attenuation, polarization rotation and phase shift. Precise knowledge of statistical expectations for rain attenuation thus is of high practical relevance. Whereas often a unique relationship between rain rate and specific attenuation is used, it is well known that the variability of drop size distributions (DSDs) is big and induces variability also in the specific attenuation vs. rain rate relationship. In this study DSD measurements in geographically and climatically different locations are evaluated and compared against the relevant ITU-R model, confirming the known geographic dependence of DSD shapes. To open such knowledge for practical applications, a proposal is made, how statistical key parameters of DSD characteristics may be included into the ITU-R DBSG3 database.