An Examination of Radar and Rain Gauge–Derived Mean Areal Precipitation over Georgia Watersheds

Abstract Compared to conventional rain gauge networks, the Weather Surveillance Radar-1988 Doppler provides precipitation estimates at enhanced spatial and temporal resolution that River Forecast Centers can use to improve streamflow forecasts. This study documents differences between radar-derived (stage III) mean areal precipitation (MAPX) and rain gauge–derived mean areal precipitation (MAP). The area of study is the headwaters of the Flint River basin, specifically the Culloden basin located in central Georgia south of Atlanta, with a drainage area of 1853 mi2. The timing of radar installations in the southeast United States provided overlapping data for only 2 yr (Jun 1996–Jul 1998). The MAP and MAPX products being examined were prepared using procedures identical to those employed operationally at the National Weather Service’s Southeast River Forecast Center. Results show that the radar (MAPX) underestimates gauge-derived rainfall (MAP) by ∼38% at the end of the 2-yr period. This underestimate is m...