Modeling the space-time evolution of rain fields: Electromagnetic wave propagation applications

Space-time (ST) multiexponential cell (MultiEXCELL), a ST correlated rainfall model oriented to the analysis of radio-propagation impairments (1 km × 1 km spatial resolution and 1-min temporal resolution), is presented. The model is developed on the basis of a comprehensive rain field database collected by the Spino d'Adda, Italy, weather radar. Rain cells are modeled using an exponentially shaped profile, whose main parameters evolve over time according to simple yet effective analytical expressions. The spatial correlation of the rain rate across the field is preserved by reproducing the natural aggregative process of single rain cells into larger clusters, while the temporal evolution of the rain field is achieved by combining the structural change of the rain cells and their displacement across the field, at the same time taking the realistic evolution of the fractional rainy area into account. When tested against local data, the time series generated by ST MultiEXCELL show to correctly reproduce the spatial and temporal correlation of the rain rate. These encouraging results suggest the use of ST MultiEXCELL as a comprehensive tool for the design and performance assessment of Earth-space and terrestrial millimeter-wave systems implementing advanced mitigation techniques relying on the uneven distribution of the rain rate in space and time.