Evaluation of Radar Precipitation Estimates from NMQ and WSR-88D Digital Precipitation Array Products: Preliminary Results

The National Mosaic and Quantitative Precipitation Estimation system (NMQ) is a joint effort among several NOAA offices, intended to test and demonstrate quantitative precipitation estimation (QPE) algorithms that are not currently implemented in the NEXRAD Precipitation Processing System (PPS). Following favorable test results and positive feedback from field users, the National Weather Service is investigating options for implementing NMQ operationally. Toward that end, we have undertaken a broad-scale evaluation and comparison of NMQ and currently-operational PPS QPE products, using real-time data from most of the conterminous United States. This effort will provide valuable guidance to field personnel, who will have access to both NMQ and PPS products and who must select and blend input from the two sources in operations. It will also serve to guide future algorithm improvement and implementation efforts.

This study evaluates products collected from the real-time NMQ prototype system, developed and maintained by the National Severe Storms Laboratory, and from mosaicked Digital Precipitation Array (DPA) products in the form of Stage2 gridded fields prepared operationally by the National Centers for Environmental Prediction. Both QPE products are compared with ASOS rain gauge reports. Verification statistics are stratified by geography and rainfall regime, in particular: (1) all cases with valid data, (2) all cases with either radar or rain gauge ≥ 0.25 mm, (3) all cases with radar or gauge ≥ 10 mm, and (4) all cases with either radar or gauge ≥ 25 mm. Initial results based on daily accumulations indicate that NMQ estimates generally have smaller errors and less statistical bias than do the DPA products, for all of the event stratifications listed above.