Intercomparison of Precipitation Estimates From WSR-88D Radar and TRMM Measurement Over Continental United States

This paper examines the spatial error structures of precipitation estimates derived from both WSR-88D ground radar measurements and National Aeronautics and Space Administration's Tropical Rainfall Measurement Mission (TRMM) satellite-based radar and passive microwave measurements. The surface and spaceborne precipitation products are systematically evaluated via comparison with the Climate Prediction Center Unified Gauge Analysis over the Continental United States (CONUS) from December 2008 through November 2010. The WSR-88D quantitative precipitation estimation (QPE) products analyzed include the national mosaic daily QPE products (Q2) and Stage II and Stage IV daily products. The TRMM QPE products analyzed include the version-7 real-time product 3B42RT and the research product 3B42 (3B42V7). The results of the comparison based on two-year mean daily precipitation over CONUS demonstrate the following: 1)3B42V7 and Stage IV perform fairly similarly with correlation coefficients (CCs) of 0.92 and 0.91, relatively low (magnitude) relative biases (RBs) of -3.32% and -7.16%, and low root-mean-squared errors (RMSEs) of 0.49 and 0.54 mm/day, respectively; 2) the gauge-corrected daily Q2 product (Q2RadGC) is slightly inferior to the 3B42V7 and Stage IV products but outperforms both the real-time satellite-only product 3B42RT and the two radar-only products (Q2Rad and Stage II) in terms of both CC and RMSE; 3) Q2Rad shows similar performance to 3B42RT regarding RB and CC; and 4) Stage II has particularly poor performance and suffers from systematic precipitation overestimation, particularly in northeastern Oregon, northern Utah, northeastern Carolina, and northern Georgia.