SIMULATION OF RADAR REFLECTIVITY FIELDS - ALGORITHM FORMULATION AND EVALUATION

A hybrid stochastic physics-based and polarization-diverse radar refle ctivity simulation procedure for rainfall studies is described. The pr ocedure begins with the generation of two-dimensional rainfall intensi ty fields from a space-time stochastic model with a statistical parame trization of drop-size distribution. The two-dimensional fields are co mplemented with a vertical structure of hydrometeors by choosing a pre cipitation cloud type model, which results in size, shape, and phase ( mixed or single) distribution at discrete elevations. Given these thre e-dimensional fields, the sampling volume integration process involved in radar measurements is simulated to give the radar-observed paramet ers. Effects such as antenna beam pattern, horizontal and vertical gra dients, atmospheric gases, and rain attenuation are represented. The r adar observables are corrupted with a random measurement error to repr esent the radar hardware system noise and other sources of uncertainty . The simulated radar reflectivities are qualitatively evaluated using actual radar data. The simulator is a useful tool for engineers and h ydrometeorologists in the study of radar-rainfall measurement and esti mation errors and their effects.