Comparison of precipitation fields estimated by gage, radar and multiple sensors (gage and radar) for SE Wisconsin and NE Illinois

Daily information on precipitation is employed year-round for purposes of water management. Real time gage data from the NWS Cooperative Network is often used, but because of spatial density limitations may not be adequate to estimate gradients in precipitation and thus inadequate to estimate precipitation over scales finer than 20-40 km.

Examples of annual, monthly and daily distributions of precipitation will be presented from 4 sources: 1) quality controlled cooperative gage data, 2) gage data from a dense (10 km) network of weighing bucket gages in Cook County, IL, 3) gridded radar estimates mosaicked and distributed by the National Center for Environmental Predication (NCEP), and 4) multi-sensor estimates produced at the NWS River Forecast Centers (RFC's) and mosaicked into a national product at NCEP. Also gage comparisons with the nearest (4x4km) gridded estimate of radar and multi-sensor data will be presented.

In general, there is good agreement between the various spatial fields on a monthly and annual basis for the years 2002-2004. Large differences, however, occur on individual days. The nature of these differences is being investigated and also will be presented.