- 1Department of Environmental Sciences and Policy, University of Milano, Via Celoria 2, 20133 Milano, Italy (jacopo.melada@unimi.it)
- 2Institute of Atmospheric Sciences and Climate (CNR-ISAC), Bologna, Via P. Gobetti 101 40129 Bologna, Italy
- 3Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 157/a, 43124 Parma, Italy
- 4Department of Earth Sciences, University of Milano, via Mangiagalli 34, 20133 Milano, Italy
- 5Department of Agricultural and Environmental Sciences, via Celoria 2, 20133 Milano, Italy
The availability of reliable hourly time series is essential for investigating the link between precipitation and debris flow events. However, before the 1990s data from weather stations are generally only available at daily resolution.
A methodology is proposed to reconstruct hourly precipitation time series from the 1940s by combining ERA5 reanalysis data — which provide hourly information — with daily cumulative values measured by in situ stations. The goal is to provide complete hourly series capable of capturing the intense precipitation events that may trigger debris flows, as required by the DECC (2023) project which investigates these gravitative phenomena at the multi-decadal scale for a study site in the area of Alpe di Succiso Mt., Northern Apennines (Italy). The analysis through time of these disruptive phenomena characterized by the rapid movement downslope of a mixture of water, rocks and debris, is a fundamental step for the hazard assessment in the context of climate change.
The algorithm automatically selects the best daily aggregation window by correlating ERA5-summed hourly precipitation with observed daily totals. ERA5’s hourly data are then corrected to match daily observed precipitation and finally ERA5’s hourly corrected data are scaled to match the distribution of the rain gauge hourly data which are available for the study area for the last decades both as station data and as gridded fields.
Daily rain gauge-based precipitation data were collected for an area within a 50 km radius from the study site from multiple regional and national providers and subjected to rigorous analysis to ensure quality and consistency. Redundant series were removed, and data were merged to establish a unique correspondence for each location. Metadata verification included checks for consistency in location coordinates and altitude, complemented by manual validation. The final dataset consists of 403 stations and was analyzed alongside gridded daily precipitation data (available from 1961) and hourly precipitation data (available from 1991), provided by the Regional Agency for Prevention, Environment, and Energy of Emilia-Romagna.
The final reconstructed hourly series is validated by comparing it with hydrological yearbook data and, for more recent periods, with rain gauge-based gridded data and hourly observations from the same stations. The reconstructed hourly series is then used in a multi-temporal analysis of dated debris flow events in Alpe di Succiso to investigate magnitude-frequency relationships and potential triggering thresholds.
References
DECC, 2023. DECC - Debris flow hazard and climate change in the Northern Apennines: reconstructing and modelling past and future environmental scenarios. PRIN 2022 PNRR - Projects of Great National Interest, Financed by the European Union – Next Generation EU. https://x.com/DECC_project/
How to cite: Melada, J., Arcuri, B., Manara, V., Brunetti, M., Chelli, A., Leonelli, G., Pescio, S., Petrella, E., Rashid, M. A., Trombino, L., Masseroli, A., and Maugeri, M.: An hourly precipitation approach to debris flow hazard assessment in the DECC project: leveraging daily rain gauge observations and hourly ERA5 reanalysis data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16938, https://doi.org/10.5194/egusphere-egu25-16938, 2025.
