Differential orographic impact on sub-hourly, hourly, and daily extreme precipitation
- 1Department of Civil, environmental and mechanical engineering University of Trento, Trento-Italy
- 2National Research Council of Italy - Institute of Atmospheric Sciences and Climate (CNR-ISAC), Bologna, Italy
- 3Department of Land Environment Agriculture and Forestry, University of Padova, Padova, Italy
Extreme precipitation in mountainous regions is the main trigger of hydrological hazards such as flash floods and debris flows, among the most dangerous natural-hazards worldwide, both for social and for economic losses. Mountains significantly influence weather and climate, including altered distribution of precipitation and of its extremes, with different impacts at different durations. Understanding the orographic impact on the statistics of precipitation extremes is therefore crucial for improving hydrological design and risk management strategies. Here, we use a novel statistical approach for the analysis of extremes based on ordinary events, which are defined as the finite independent samples of the analyzed stochastic process (e.g. Marani and Ignaccolo, 2015), to improve our understanding of the orographic impact on extreme precipitation of durations ranging between 5 minutes and 24 hours. We focus on Trentino, a rough orographic region in the eastern Italia Alps, and use data from 78 quality-controlled rain gauges with 5-minute resolution. We validated our statistical framework against statistical properties of the observed annual maxima (Nash-Sutcliffe and Bias) as well as their relation with orography. We then exploit the reduced uncertainty of this approach to quantify the orographic impact on precipitation right-tail statistics and on extreme return levels using a regression analysis. We identify two main modes of orographic relationship: a reverse orographic effect for hourly and sub-hourly durations and an orographic enhancement for durations of ~8 hours or longer. We observe that these two modes result from three main precipitation regimes, which show different proportion between extreme and very-extreme events and which emerge at very short durations mid durations and long durations. These findings are of interest for risk management applications and climate change impact studies.
References
Marani, M., & Ignaccolo, M. (2015). A metastatistical approach to rainfall extremes. Advances in Water Resources, 79, 121-126.
How to cite: Formetta, G., Marra, F., Dallan, E., Zaramella, M., and Borga, M.: Differential orographic impact on sub-hourly, hourly, and daily extreme precipitation , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-549, https://doi.org/10.5194/egusphere-egu22-549, 2022.
