Precipitation estimates by radar : a zenith pointing radar perspective

Data collected from zenith pointing radar is used to study the range dependence of some meteorological radar errors associated with different sampling methods between radar and gauges in stratiform precipitation. Errors due to the vertical variation of reflectivity such as those related with the bright band or with snow growth cause a much larger bias in radar estimates than those due to beam filling or gradients. The maximum useful range varies with the bright band height and the elevation angle program used, a CAPPI giving superior results especially for snow. The sudden changes in bright band height over short distances and the large scatter of its thickness limit the accuracy of current corrections for the vertical variation of reflectivity based on scanning radar data. The possibility of using a zenith pointing radar to obtain this correction is discussed