Dual-pol VPR Corrections for Improved Operational Radar QPE in MRMS Journal of Hydrometeorology

The radar bright band is caused by melting ice crystals, and results in inflated reflectivity observations. If uncorrected, the bright band can result in large errors in radar-derived quantitative precipitation estimation (QPE). In the operational Multi-Radar Multi-Sensor (MRMS) system up to version 12.1, the effects of the bright band are corrected through the use of a reflectivity-only, tilt-based apparent vertical profile of reflectivity (tilt-VPR). This study utilizes dual-pol radar observations to improve the tilt-VPR methodology. To accomplish this, a bright band area delineation was developed within the MRMS framework and the bright band top and bottom heights were identified for individual tilts of radar data. This information was used to develop a radially-dependent dual-pol VPR (dpVPR) model which can better correct reflectivity in situations of non-isotropic bright bands and low bright band events. This algorithm has been tested on 14 varying bright band events across the CONUS and compared with the tilt-VPR and the National Weather Service Weather Surveillance Radar – 1988 Doppler Level-3 Digital Precipitation Rate (DPR) products. The radially-dependent dpVPR correction provided a more accurate detection of bright band areas and a more effective reduction in QPE errors within and above the bright band than the tilt-VPR and DPR QPEs, especially for precipitation events with low melting layers or with strong variability of vertical motions. The bright band delineation and dpVPR methodology are also evaluated in the real-time MRMS testbed for their robustness and computational efficiency and has been transitioned into operations in 2022. Grant no. NA11OAR4320072