Can we reliably estimate precipitation with high resolution during disastrously large floods?

Abstract. A huge and dangerous flood occurred in September 2024 in the upper and middle Odra river basin, including mountainous areas in south-western Poland. The widespread precipitation lasted about four days, reaching more than 200 mm daily. In order to verify the possibilities of precise estimation of the precipitation field, different measurement techniques were analysed: rain gauge data, weather radar-based, satellite-based, non-conventional (CML-based) and multi-source estimates. Apart from real-time and near real-time data, later available reanalyses based on satellite information (IMERG, PDIR-Now) and numerical mesoscale model simulations (ERA5, WRF) were also examined. Manual rain gauge data for daily accumulations and multi-source RainGRS estimates for hourly accumulations were used as references to evaluate the reliability of the various techniques for measurements and estimation of precipitation accumulations. Statistical analyses and visual comparisons were carried out. Among the data available in real time the best results were found for rain gauge measurements, radar data adjusted to rain gauges, and RainGRS estimates. Fairly good reliability was achieved by non-conventional CML-based measurements. In terms of offline reanalyses, mesoscale model simulations also demonstrated reasonably good agreement with reference precipitation, while poorer results were obtained by all satellite-based estimates except the IMERG.