Physically Based Two-Dimensional Seamless Mosaic for Radar QPE in a national network

The U.S. Weather Surveillance Radar-1988 Doppler (WSR-88D) network, since its deployment in mid-1990s, has provided meteorologists and hydrologists with quantitative precipitation observations at an unprecedented high spatial-temporal resolution. Since each of the radar only covers a maximum range of 460km, a mosaic of the radar data is needed to generate any national products. In the Multi-Radar Multi-Sensor (MRMS) system, a physically based 2-D mosaic of the WSR-88D data was developed for a seamless national quantitative precipitation estimation (QPE) product. In areas with one radar coverage only, the mosaic takes the single radar observations. In areas with multiple radar coverage, the mosaic first determines if precipitation is present by checking the lowest altitude observation. If the lowest observation indicates no precipitation, then the mosaicked value will be set to no precipitation. Otherwise, a weighted mean mosaicking of multiple radar observations are taken as the mosaicked value. The weighting function is based on multiple factors including the distance from the radar and the height of the observation with respect to the melting layer. The mosaic tries to use the lowest unblocked radar observations while maintaining a spatial continuity in the mosaicked field. The performance of the MRMS seamless radar mosaic was examined for many precipitation events of different characteristics and the results will be presented at the conference.