Abstract
Operational weather radar data have been compared with surface rain gauge measurements to quantify the uncertainties in radarβderived surface rainfall values over upland areas. This comparison is necessary to assess the potential of radar data for flood forecasting and warning in nonβgauged upland catchments. Radar rainfall accumulations across three contrasting upland catchments in England and Wales over a 12βmonth period are compared with surface rain gauge measurements. Results show that the addition of orographic corrections applied as part of the operational radar data processing chain leads to considerable improvement in the quantitative accuracy of the derived surface rainfall, typically reducing the error between radar and gauge measurements by 50%. Comparison of rainfall accumulations during specific events shows that radar data quality over upland areas is currently insufficient for quantitative use as a reliable flood warning tool in nonβgauged upland catchments. Only about 50% of rainfall events when in excess of 30 mm recorded by surface gauges are diagnosed as exceeding that threshold by the corrected radar data. Β© Crown copyright 2007. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd