Modeling of rain fields at large scale

This paper describes the modeling of rain fields at small (size of a rain cell) mid (100times100 km²) and very large scale (4000times4000 km²). The methodology lies on a cellular description of rain fields by HYCELL Mid-scale fields are generated so that they account for local climatology and for spatial repartition of rain cells deduced from radar data. Very large scale fields are generated in two steps. First rainy areas are determined by thresholding a stationary Gaussian random field. In each point of the field, the probability of rain apparition is the one recommended by ITU and the covariance function is determined in order to reproduce the one observed by meteorological radar. Then rain intensity for rainy area is determined by applying mid-scale model to each mid-scale rainy area. Rain fields simulated are turned into attenuation fields and compared with ITU-R recommendations and radar observations