COMPARING MEAN AREAL PRECIPITATION ESTIMATES FROM NEXRAD AND RAIN GAUGE NETWORKS

Mean areal precipitation values (MAPX) derived from next generation weather radar (NEXRAD) stage III data are compared with mean areal precipitation (MAP) values derived from a precipitation gauge network. The gauge-derived MAPs are computed using Thiessen polygon weighting, whereas the radar-based MAPXs utilize the gridded stage III radar precipitation products that have been conditioned with gauge measurements and have been merged with overlapping radar fields. We compare over 4,000 pairs of MAPX and MAP estimates over a 3-year time period for each of eight basins in the southern plains region of the United States. Over the long term, mean areal estimates derived from NEXRAD generally are 5-10% below gauge-derived estimates. In the smallest basin, the long-term MAPX mean was greater than the MAP. For storm events, a slight tendency for NEXRAD to measure fewer yet more intense intervals of precipitation is identified. Comparison of hydrologic simulations using the two forcings indicates that significant differences in runoff volume can result. This work is aimed at providing insight into the use of a data product that is becoming increasingly available for public use. It also is aimed at investigating the use of radar data in hydrologic models that have been calibrated using gauge-based precipitation estimates.