Dual Polarization Quantitative Precipitation Estimation on the WSR-88D: Current Status and Future Plans

The 2011 upgrade of the NEXRAD Weather Surveillance Radar-88D Doppler (WSR-88D) network to dual polarization (Dual Pol) included a suite of quantitative precipitation estimation (QPE) products, including the Digital Instantaneous Precipitation Rate (DPR), the hourly One Hour Accumulation (OHA) and Digital Accumulation Array (DAA), two storm total accumulation products (Storm Total Accumulation (PTA) and Digital Storm Total Accumulation (DTA)), hourly and storm total difference products (“legacy” vs. dual pol), and the Digital User-Selectable Accumulation (DU3/DU6).

Algorithm updates in recent years have been made to improve quality control/removal of non-precipitation echoes and to improve precipitation estimates within the melting layer, but the current Dual Pol QPE algorithms remain largely the same as the versions that were originally deployed operationally in 2011. This long period of stability has allowed for a comprehensive assessment, conducted by the National Severe Storms Laboratory in collaboration with the Radar Operations Center, of the Dual Pol QPE’s performance relative to other QPE products available in operations such as the Legacy QPE on the WSR-88D and Multi-Radar Multi-Sensor (MRMS) mosaic QPE. Additionally, new dual pol-based methods for precipitation estimation have emerged that have the potential to improve QPE accuracy, such as the specific attenuation rain rate as a replacement to the existing R(Z,ZDR) relationships that tend to be sensitive to errors in differential reflectivity and require forecaster intervention to choose between “continental” and “tropical” relationships.

The purpose of this presentation is to summarize the current state of the WSR-88D Dual Pol QPE and to provide a preview of planned updates plus the net impacts the changes will have on the QPE product performance.