An Update on the Operational Multi-Radar Multi-Sensor QPE

The operational Multi-Radar Multi-Sensor (MRMS) system has provided users with a suite of high resolution (1-km, 2-min) quantitative precipitation estimation (QPE) products since its deployment at the National Weather Service (NWS) in 2014. One of the MRMS product suites is the radar-based QPE that has little latency and is used for flash flood warnings and situational awareness. The radar QPE was based on a combination of specific attenuation (A), specific differential phase (Kdp) and reflectivity (Z) fields and their relationships with precipitation rates (R). It consists of several major components: 1) radar data quality control to remove non-hydrometeor echoes; 2) standard and non-standard blockage corrections; 3) vertical profile of reflectivity correction for bright band and beam overshooting effects; 4) precipitation type classification for using adaptive R(Z) relations; and 5) precipitation rate estimation based on a synthetic of R(A), R(Kdp) and R(Z) relationships.

During the last a few years, several updates are implemented in the MRMS radar QPE. The updates included enhancements to the radar data quality control to handle corrupt data associated with hardware issues and to reduce wind farm contaminations. A dual-pol vertical profile of reflectivity correction was developed to improve rainfall estimation accuracy in areas where the lowest radar tilt intersects the melting layer (which often results in a radar QPE overestimation) or overshoots the melting layer (underestimation). Further, a refinement was developed to the specific attenuation based rain rate estimates to reduce errors associated with large spatial variations of the drop size distribution (DSD). Those errors were due to an approximation in the R(A) method that assumes a relatively uniform DSD in the radar domain. An overview of these updates and an outlook for the future development in the operational MRMS QPE will be presented at the conference.