Considerable efforts have been directed to adjusting the radar-rainfall estimates provided by the
NEXRAD radars. In general, the procedures developed involve some correlation of the reflectivitybased
estimates with ground-based rain gauges. This topic was discussed in more detail in Chapter 5
(GIS for Surface-Water Hydrology). Seo et al. (1999) summarized the background research and
described the National Weather Service (NWS) procedures that estimate mean field bias in real
time. To reduce systematic errors in radar-rainfall data due to lack of radar calibration and inaccurate
Z–R relationships (i.e., the multiplicative constant), precipitation estimation by the NWS
(Fulton et al. 1998) uses procedures that estimate radar umbrella-wide biases in radar-rainfall data
in real time (Seo and Breidenbach 2002). The estimated “mean field bias” is then applied to the
entire radar umbrella to produce “bias-adjusted” radar-rainfall data.