Simulation of the orographic influence on weather radar using a geometric-optics approach

A computer code for radar site assessment, including ground clutter, beam o ccultation, and earth curvarure-atmospheric refraction factors. has been de veloped. The code uses topographic information in the form of a raster Digi tal Elevation Model, air refractive index profile in the boundary layer, su rface backscattering cross section per unit area at grazing angles as deriv ed from literature, and ancillary information, if available, derived from a land use-land cover map. This algorithm is independent of a specific radar site and radar system. Several benefits in dealing with open problems of r adar meteorology and of radar design could be derived from its use, namely, better estimate of precipitation at ground level through vertical echo pro file correction, scanning strategy, land clutter measurements at low grazin g angles, and characterization of seasonal and topographic effects. The ras ter-based approach used in implementing the code makes it compatible with a ny spatial resolution desired. Simplicity and short simulation times have b een pursued as primary goals during the planning and implementation phases of the code. The result is a standard ANSI FORTRAN software that is portabl e, easy to use, and runs on an IBM-compatible PC. In its simplest version, the model needs only a raster Digital Elevation Model, the radar parameters , and an estimate of the mean atmospheric refraction.