Differences in multi-sensor and rain-guage precipitation amounts

A comparison of multi-sensor (radar and gauge) and gauge precipitation estimates at a monthly temporal resolution and a county spatial resolution was undertaken for the midwestern USA. Precipitation data were collected from February 2002 to October 2006 from two sources: (a) multi-sensor precipitation estimates (MPE) based on the stage III/IV algorithm developed by the US National Oceanic and Atmospheric Administration (NOAA), national weather service (NWS) office of hydrology and NWS river forecast centres; and (b) quality-controlled NWS cooperative rain-gauge (QC-Coop) data from the NOAA national climatic data centre (NCDC). The gauge data were employed as the reference standard. The monthly median of the percentage differences in countyaveraged monthly precipitation estimated by MPE and QC-Coop in the midwestern USA, for around 750 counties, was mainly within ±12.5%, with a median percentage difference of +6%. The positive difference indicates that, overall, the MPE values tend to be smaller than the QC-Coop values. ME values more closely correspond with QC-Coop values at all latitudes in the summer months when convective precipitation is dominant, and in the winter months for latitudes where non-frozen precipitation is most prevalent.