Update the Blockage Data for WSR-88D Radars Used in the MRMS System

Accurate information about the blockage plays an important role in the proper interpretation of reflectivity data. In the Multi-Radar-Multi-Sensor (MRMS) system, the occultation data affects both severe weather and quantitative precipitation estimation (QPE) products. With the MRMS system transitioned into operations in 2014, forecasters reported occasional removal of weather echoes and inaccurate power correction due to inaccurate beam blockage information. The potential sources of the error may come from: 1) the terrain data resource used in the MRMS; 2) the raw resolution of blockage field; 3) conservative blockage parameter settings to avoid ground clutter in the single-pol radar era; and 4) outdated information of non-standard blockage from manmade buildings or trees. To update the blockage files for all US WSR-88D radars in the MRMS system, in the first step, this work examines the reliability of various terrain data resources to find an accurate data set for the radar blockage estimation. The second step is to refine our blockage calculation method and adjust the parameter settings that are optimal for the dual-pol radar era.  After updating the blockage data, the non-standard beam blockage mitigation parameters will be updated. The update will improve the MRMS performance in storm detection, forecasting, as well as the precipitation products, which benefits all the MRMS users.