Abstract
The overarching objective of ENCIRCLE is to provide credible, understandable and useful information of how climate change affects the frequency, intensity and duration of precipitation extremes driven by extratropical and Mediterranean cyclones in Italy. We identify the lack of high-resolution multi-member climate simulations as the key limit in evaluating changes in these events, and overcome it by developing a novel statistical-dynamical framework to assess risk that exploits - in an unprecedented way - the respective strengths of available high-resolution regional climate models (RCMs) and initial condition single-model large ensembles (SMILEs). The former provide a better representation of regional processes, while the latter have a sufficient number of ensemble members to isolate the signal of climate change from internal climate variability. RCMs and SMILEs are usually analysed by different communities, but ENCIRCLE aims to demonstrate that a substantial advancement in the assessment of regional hydroclimatic hazards can be obtained via a coordinated analysis. Expected results: ENCIRCLE will extract complementary climate information from the SMILES and from RCMs via a deep learning approach that learns from observations the most favourable circulation patterns that trigger regional precipitation extremes. ENCIRCLE results will advance current knowledge on the impact of climate change on the frequency of cyclones and on the magnitude of the associated precipitation extremes in Italy, and thus clarify the role of climate change in recent extreme precipitation events. The role of physical processes, such as the shifts of mid-latitude jets and the warming of the Mediterranean sea, as a source of uncertainty in the projections will be made transparent, and summarised in the form of interpretable storylines of regional climate change. This will provide a range of best and worst-case scenarios to support the planning and development of adaptation policies.
Results achieved
: The 2022 PRIN ENCIRCLE project investigated how climate change is altering the frequency and intensity of extreme cyclone-related rainfall in the Mediterranean region and in Italy. The goal was to combine actual observations, historical data, and model simulations to distinguish the signal of climate change from natural climate variability, which is particularly pronounced in extreme events. A key initial result was the creation of a new classification of atmospheric patterns that cause extreme rainfall in Italy. Using an artificial intelligence technique (Self-Organizing Maps), ENCIRCLE identified a set of typical meteorological configurations (“Weather Types”), defined by atmospheric pressure and sea-level temperature, each associated with different conditions for cyclone formation, moisture transport, and seasonality. This classification made it possible to identify the main atmospheric “regimes” affecting the entire peninsula and served as the basis for a catalog of extreme precipitation events associated with cyclones, compiled by integrating various observational data sources and climate reconstructions. Furthermore, this analysis of recent history has shown an increase in the frequency of extreme precipitation events in Italy over the past few decades. Another outcome of ENCIRCLE was the development of a method that breaks down the overall risk of extreme rainfall into three factors: the probability that favorable atmospheric conditions will form, the probability that, given those conditions, a cyclone will develop, and the probability that the cyclone will generate extreme rainfall along its path. When applied to two high-impact historical events—the 1966 Florence flood and the 2018 Storm Vaia—the method showed that, under the moderate emissions scenario SSP2-4.5, the overall probability of similar events would remain stable through the end of the century: a reduction in favorable atmospheric conditions would in fact be offset by an increase in the probability that, when those conditions do occur, they will lead to extreme rainfall. It also emerged that the intensification of extreme rainfall depended heavily on the type of atmospheric configuration: cyclones in the western Mediterranean involving the Alps, such as Storm Vaia, showed an increase in both average and extreme rainfall, while other types of cyclones could even weaken. Finally, by analyzing high-resolution simulations from the European Destination Earth project, the researchers isolated the direct effect of global warming on rainfall, while holding the atmospheric configuration constant. The result was an increase in extreme rainfall across much of Italy, with significant differences between regions and seasons. Recent high-impact events, such as Storm Vaia and the Emilia-Romagna flood of May 2023, were intensified by global warming more than the expected average (approximately 7% more for every degree of global temperature increase). The project produced a scientific article published in the *International Journal of Climatology* (https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.70118), focusing on the classification of high-risk atmospheric patterns, while other articles on the attribution of extreme events and changes in atmospheric regimes were in preparation at the end of the project. A second article, based on Destination Earth data and focusing on the direct effect of global warming on extreme rainfall, is currently under review at Environmental Research Letters (ERL) and is expected to be accepted shortly. Three additional articles, focusing on the attribution of extreme events and changes in atmospheric patterns, are currently in preparation and will be submitted in the coming months. The code developed as part of the project has been made publicly available on GitHub to facilitate the reproducibility of the research. ENCIRCLE also fostered dialogue between the research community and local stakeholders through a dedicated workshop titled “Extreme Precipitation in Italy: Understanding, Impacts, and Future Prospects,” (https://encircle.odoo.com/workshop-precipitazioni), which brought together researchers, operational services, and institutions, providing tools and knowledge useful both for understanding the evolution of extreme rainfall in Italy and for concretely supporting climate change adaptation strategies. Furthermore, ENCIRCLE’s results have been disseminated through national and international scientific conferences (AISAM 2026, EGU 2025–2026, EMS 2025)Project details
Unibo Team Leader: Salvatore Pascale
Unibo involved Department/s:
Dipartimento di Fisica e Astronomia "Augusto Righi"
Coordinator:
CNR - Consiglio Nazionale delle Ricerche(Italy)
Total Unibo Contribution: Euro (EUR) 89.800,00
Project Duration in months: 24
Start Date:
28/09/2023
End Date:
28/02/2026
