Real-time High Resolution Precipitation Estimation with the CASA DFW Urban Demonstration Network (Invited Presentation)

Accurate estimation of rainfall rates and amounts in a timely manner is critical to flash flood prediction and mitigation. Dual-polarization radar can observe precipitation over a wide area in a relatively short period of time. It has been used as primary system for quantitative precipitation estimation (QPE) in many nations. Currently, the National Weather Service (NWS) Weather Surveillance Radar – 1988 Doppler (WSR-88DP) network provides radar data with updates every five-six minutes across the United States. Though the NWS radar-based rainfall products provide us with general information about rainfall amount and distribution, the coarse resolution limits the applications such as urban flash flood monitoring, which can occur a few minutes after local torrential rainfall due to urban characteristics such as impervious cover and complex drainage systems. To overcome the fundamental coverage limitation of WSR-88DP radar, and improve the spatial-temporal resolution, the National Science Foundation Engineering Research Center (NSF-ERC) for Collaborative Adaptive Sensing of the Atmosphere (CASA) was founded to improve weather sensing in the lower atmosphere by deploying a dense network of shorter-range, low-power X-band dual-polarization radars.

As the first urban test bed, CASA Dallas–Fort Worth (DFW) Urban Demonstration Network consists of a combination of high resolution X-band radar network and a standard S-band WSR88-DP radar (i.e., KFWS radar). This paper presents the real-time high-resolution QPE system developed for this urban radar network. The QPE system is designed via fusion of observations from both the X-band radar network and S-band KFWS radar. The specific dual-polarization radar rainfall algorithms at S- and X-band frequencies, as well as the fusion methodology combining observations at different temporal resolution will be presented. Cross-comparisons between radar rainfall estimates and rainfall measurements from ground rain gauges have demonstrated the excellent performance of CASA DFW urban QPE system. Coupled with hydrologic models, the high-resolution real-time rainfall products are being used for urban flash flood forecasting for DFW area.