MRMS Version 12 QPE Products Update—2018/2019

The Multi-Radar Multi-Sensor (MRMS) quantitative precipitation estimation (QPE) system is undergoing a major update from version 11.5 to 12 at the National Severe Storms Lab. This update includes the following changes:

• A new dual-pol radar synthetic QPE product will be implemented and replace the old MRMS radar QPE that was based on multiple R(precipitation rate)-Z(reflectivity) relationships. The new dual-pol radar QPE was based on combinations of reflectivity, specific differential phase, and specific attenuation. The use of specific attenuation has been shown to provide improved accuracy (less underestimation) in heavy to extreme precipitation across the CONUS, and the use of specific differential phase provides improved QPE in areas of hail. Furthermore, an evaporation correction was applied to the dual-pol radar QPE that will reduce overestimation biases and false light precipitation seen in the MRMS radar-based QPE where drier air exists between the radar beam level and the ground (e.g., the semi-arid regions of the southwestern US).
• A new multi-sensor QPE that combines the MRMS dual-pol radar QPE, gauges, precipitation climatology, satellite QPE, and numerical weather prediction (NWP) model quantitative precipitation forecast (QPF) will be implemented. This product will retain the high-resolution precipitation distribution in radar observations and apply a local gauge correction for accurate QPE intensities. Satellite QPE, NWP QPF, and gauge/climatology data are applied in areas of poor radar via a physically based merging scheme to assure the spatial continuity of the merged QPE. The multi-sensor QPE provides a single unified product with a better accuracy than each single input source across the MRMS domain.
• The new MRMS system will be implemented to several oCONUS domains including Hawaii, Alaska, the Caribbean, and Guam whereby the QPE products will be evaluated for each domain.

This paper will provide an overview of the MRMS QPE version 12 updates and their impacts.