Considerations of Rain Cell Size and Statistics for Attenuation Prediction Models

Physical-based rain attenuation prediction models conventionally assume a deterministic dependence of rain cell size on rainfall rate and uniaxial structure. This study examined the impact of these assumptions on attenuation predictions. In comparison with model predictions that apply an exponential distribution of cell sizes, the deterministic models exhibited a small cell size effect in which the attenuation exceedance probability was clamped due to the limited path through the rain cell. This resulted in an under-estimation of attenuation in many cases. A biaxial rain-cell attenuation prediction capability was developed to model observed biaxial rain cell shapes and orientational distributions.