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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #103636
Title: EFFECT OF BIAS ADJUSTMENT AND RAIN GAUGE DATA QUALITY CONTROL ON SPATIAL RADAR RAINFALL ESTIMATION

Author
item STEINER, M - PRINCETON UNIVERSITY
item SMITH, J - PRINCETON UNIVERSITY
item BURGES, S - UNIVERISTY OF WASHINGTON
item Alonso, Carlos
item Darden, Robert

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Access to accurate, distributed precipitation data is the most significant factor that affects our ability to make optimum decisions in agricultural production, water resources management, and soil conservation practices. This paper describes ongoing research aimed at showing how to combine weather radar, rain gauges, and special instruments for measuring raindrop-size distributions to provide rainfall rate, while covering large areas at high spatial and temporal resolution. Precipitation data collected by the Memphis, Tennessee NEXRAD radar station during thirty major storms that passed over the Goodwin Creek Watershed have been analyzed. The results show the importance of adjusting the radar rainfall estimates using rain gauge data, the need for good quality control of rain gauge measurements, and the sensitivity of radar-based rainfall estimates to variability of raindrop-size distribution among and within storm events. As our ability to use weather radar information to augment data from sparse rain gauge networks increases, so will the potential benefits of using radar to provide comprehensive coverage of major storms passing over large areas that are subject to flooding or soil erosion. This capability will in turn result in better estimates of potential soil erosion by raindrop impact, and better assessment of soil conservation measures.

Technical Abstract: Thirty major storms that passed over Goodwin Creek...were analyzed to assess the bias of radar rainfall estimates at rain gauge locations to the gauge amounts under various radar data processing scenarios. The focus of this study was to demonstrate the importance of (1) bias adjustment of the radar rainfall estimates and (2) the quality control of the rain gauge data used for bias adjustment. The analyses are based on Memphis WSR-88D radar data, tipping-bucket rain gauge data, and raindrop spectra information...Our results show that without bias adjustment, the radar rainfall estimates at gauge locations generally underestimate the rain gauge amounts. This underestimation of rainfall by radar requires a bias adjustment using gauge point-rainfall observations to provide the best spatial rainfall information. But tipping-bucket rain gauges are prone to malfunctioning caused frequently by biological and mechanical fouling, and human interference... Therefore, careful quality control of the rain gauge data is crucial, and only good-quality rain gauge information should be used for bias adjustment of radar rainfall estimates....lower... level at which the radar-measured reflectivity is truncated ...resulted in smallest RMSE differences between the radar rainfall estimates at the gauge locations and the rain gauge amounts.