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 event provided an opportunity to investigate the feasibility of a reliable estimation of a high-resolution precipitation field, which is crucial for effective flood protection. Data from different measurement techniques were analysed: rain gauges, weather radars, satellites, and commercial microwave links (CMLs) and multi-source estimation. 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. Reference data used to verify the reliability of the different techniques for the measurement and estimation of precipitation included observations from manual rain gauges and multi-source estimates from the RainGRS system developed at the Institute of Meteorology and Water Management – National Research Institute (IMGW) for daily and hourly accumulations, respectively. 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 IMERG.