Empirically based modelling of radar-rainfall uncertainties for a C-band radar at different time-scales

Radar-based estimates of rainfall are affected by several sources of systematic and random errors. The propagation of these uncertainties is required for improving the understanding and interpretation of the results obtained when radar-rainfall estimates are used as input or initial conditions. Despite the relevance of the problem, modelling of radar-rainfall uncertainties is still at an early stage. The authors apply an empirically based model in which the relation between true rainfall and radar-rainfall can be described as the product of a systematic distortion function (accounting for systematic biases) and random component (describing the remaining random errors). The proposed results are based on a large sample (more than six years) of data from a C-band radar (Wardon Hill) located in southwest England. The true ground rainfall is approximated by rain gauge measurements from a highly dense network deployed in the Brue catchment, located about 40 km from the radar site. The authors present results from their modelling of the radar-rainfall errors at four time-scales of hydrologic interest (5- and 15-minute, hourly and three-hourly) and 2 km spatial resolution, discussing the impact of spatial sampling errors on the proposed results. Copyright (C) 2009 Royal Meteorological Society