Radar Beam Blockage Processes in the Multi-Radar Multi-Sensor System

Radar data is one of main data sources for the generation of various severe weather and quantitative precipitation estimation (QPE) products in the Multi-Radar-Multi-Sensor (MRMS) system. And the quality of the products are impacted by radar beam blockage, especially in the mountainous regions of the western US and Appalachians. In MRMS, blockage tables are calculated for each of radars using high-resolution digital elevation model (DEM) data assuming a standard atmosphere and a Gaussian power density distribution in the radar beam. Further, blockage from growing trees, man made towers and buildings and other objects that are not represented in the DEM data is manually identified and recorded from long-term precipitation accumulations. Such blockage information constitutes the so-called non-standard blockage mitigation tables in MRMS. The blockage information is used to screen out data that are significantly blocked and for correction of reflectivity observations that are slightly or moderately blocked. Different applications and products can have different tolerance for the blockage severity. This paper provides an overview of the blockage processes in the MRMS system and their impact on the product quality.