Periodic Reporting for period 1 - UMBRELLE (Understanding mechanisms behind reliable future extreme precipitation estimation over Europe)
Berichtszeitraum: 2022-01-01 bis 2023-12-31
The UMBRELLE project addressed a pressing societal need for reliable local climate information on the future changes in the most intense rainfall events in Europe, a region characterized by low confidence in future extreme precipitation changes. These extreme events are costly, deadly and pose significant risks to society, resulting in flooding, landslides and economic losses. UMBRELLE provided research of high relevance to stakeholders, policy-makers, and the wider public to facilitate their understanding of climate-related risks and inform adaptation efforts.
The lack of knowledge in projecting changes in extreme precipitation in Europe can be partly explained by the variety of mechanisms involved, from local (e.g. convective processes) to hemispheric (e.g. atmospheric circulation) spatio-temporal scales. The research carried out in UMBRELLE directly addressed this issue, assessing the physical mechanisms involved in heavy precipitation events to better understand their response to warmer conditions. The project improved our understanding by overcoming key limitations in climate modelling related to the representation of deep convective processes and the assessment of future regional atmospheric circulation changes.
The first objective of UMBRELLE focused on realistically simulating observed cases of extreme precipitation events using advanced climate modelling techniques, by explicitly simulating the processes of atmospheric deep convection at kilometer-scale spatial resolution. The second objective was to identify plausible future pathways for the atmospheric circulation over Europe using a unique 'storylines' approach that considers different scenarios from state-of-the-art climate models. Finally, the third objective was to assess how these extreme precipitation events may change in response to future warmer conditions, using innovative simulations to understand the underlying mechanisms driving these future changes.
The lack of knowledge in projecting changes in extreme precipitation in Europe can be partly explained by the variety of mechanisms involved, from local (e.g. convective processes) to hemispheric (e.g. atmospheric circulation) spatio-temporal scales. The research carried out in UMBRELLE directly addressed this issue, assessing the physical mechanisms involved in heavy precipitation events to better understand their response to warmer conditions. The project improved our understanding by overcoming key limitations in climate modelling related to the representation of deep convective processes and the assessment of future regional atmospheric circulation changes.
The first objective of UMBRELLE focused on realistically simulating observed cases of extreme precipitation events using advanced climate modelling techniques, by explicitly simulating the processes of atmospheric deep convection at kilometer-scale spatial resolution. The second objective was to identify plausible future pathways for the atmospheric circulation over Europe using a unique 'storylines' approach that considers different scenarios from state-of-the-art climate models. Finally, the third objective was to assess how these extreme precipitation events may change in response to future warmer conditions, using innovative simulations to understand the underlying mechanisms driving these future changes.
The UMBRELLE project explored how case studies of high impact observed extreme precipitation events might respond to climate change, through comprehensive analyses of the mechanisms controlling their changes. On 1 October 2020, the extra-tropical storm Alex hit western France, bringing heavy rainfall and flooding. It initiated a south-westerly atmospheric flow in the Mediterranean Sea, which led to the development of a Mediterranean heavy precipitation event in the French and Italian Alpine regions. This Mediterranean event was of rare intensity, with record-breaking precipitation that caused severe flooding and landslides, killing at least 10 people, and causing economic losses of about 1 billion euros. This sequence of the mid-latitude storm Alex and the intense convective Mediterranean heavy precipitation event in 2020 was therefore highly relevant to UMBRELLE and was selected for its uniqueness, the diversity in the nature of the two successive events, and their societal impacts.
Key achievements of UMBRELLE include the realistic simulation the observed event in October 2020, using the CNRM-AROME model. The simulations accurately reproduced the characteristics and impacts of extreme rainfall, providing valuable insights into the underlying mechanisms. This was achieved by the kilometer-scale spatial resolution that enables processes of deep atmospheric convection to be explicitly resolved. The accuracy of the simulated precipitation was established by comparison of high quality and high resolution observations merging rainfall estimates from radars and gauges.
Besides, UMBRELLE assessed the impacts of a warmer world on the intense Mediterranean heavy precipitation event observed in 2020. By conducting sensitivity experiments with different sea surface temperature conditions, the project demonstrated the intensifying effect of warmer sea surface temperatures on extreme precipitation, as well as the potential shift in local precipitation patterns. A plausible worst case scenario of the observed extreme precipitation event occurring in 2022 instead of 2020, with warmer sea surface temperatures, was tested and contextualized with idealized experiments. This research highlighted the limited impact of the changes in storm Alex compared to regional Mediterranean warming in explaining extreme precipitation changes during the Mediterranean event. Results showed that warmer sea surface temperature lead to increased humidity and instability advected by the low-level atmospheric flow over the mountainous region where deep convection is enhanced locally. This storyline shows a milder precipitation-related risk in the French Alpine region, but increased damage in Italy, information that is highly relevant for stakeholders and climate-related risk assessment.
Another aspect of the research concerned the larger scales of the atmospheric circulation, based on a large ensemble of state-of-the-art Earth System Models. UMBRELLE demonstrated the need for a seasonal focus when assessing the climate drivers of changes in extreme precipitation in the Mediterranean basin. An innovative methodology was developed to identify plausible future pathways for the atmospheric circulation over Europe from the different responses given by the ensemble of models, and to test these circulation changes on the observed extreme precipitation event.
In terms of exploitation and dissemination, the project has actively communicated its findings through publications in international peer-reviewed journals, presentations at conferences and workshops, and engagement with the wider public. These efforts have contributed to advancing scientific knowledge in the field of extreme precipitation and have practical implications for adaptation and resilience strategies in the face of climate change.
Key achievements of UMBRELLE include the realistic simulation the observed event in October 2020, using the CNRM-AROME model. The simulations accurately reproduced the characteristics and impacts of extreme rainfall, providing valuable insights into the underlying mechanisms. This was achieved by the kilometer-scale spatial resolution that enables processes of deep atmospheric convection to be explicitly resolved. The accuracy of the simulated precipitation was established by comparison of high quality and high resolution observations merging rainfall estimates from radars and gauges.
Besides, UMBRELLE assessed the impacts of a warmer world on the intense Mediterranean heavy precipitation event observed in 2020. By conducting sensitivity experiments with different sea surface temperature conditions, the project demonstrated the intensifying effect of warmer sea surface temperatures on extreme precipitation, as well as the potential shift in local precipitation patterns. A plausible worst case scenario of the observed extreme precipitation event occurring in 2022 instead of 2020, with warmer sea surface temperatures, was tested and contextualized with idealized experiments. This research highlighted the limited impact of the changes in storm Alex compared to regional Mediterranean warming in explaining extreme precipitation changes during the Mediterranean event. Results showed that warmer sea surface temperature lead to increased humidity and instability advected by the low-level atmospheric flow over the mountainous region where deep convection is enhanced locally. This storyline shows a milder precipitation-related risk in the French Alpine region, but increased damage in Italy, information that is highly relevant for stakeholders and climate-related risk assessment.
Another aspect of the research concerned the larger scales of the atmospheric circulation, based on a large ensemble of state-of-the-art Earth System Models. UMBRELLE demonstrated the need for a seasonal focus when assessing the climate drivers of changes in extreme precipitation in the Mediterranean basin. An innovative methodology was developed to identify plausible future pathways for the atmospheric circulation over Europe from the different responses given by the ensemble of models, and to test these circulation changes on the observed extreme precipitation event.
In terms of exploitation and dissemination, the project has actively communicated its findings through publications in international peer-reviewed journals, presentations at conferences and workshops, and engagement with the wider public. These efforts have contributed to advancing scientific knowledge in the field of extreme precipitation and have practical implications for adaptation and resilience strategies in the face of climate change.
The UMBRELLE project has made significant progress beyond the state of the art in understanding extreme precipitation events and their future evolution. By addressing key limitations in climate modeling and exploring novel approaches, the project has advanced our knowledge in several key areas.
Expected results following UMBRELLE achievements include:
• Further refinement of climate modeling techniques to improve the accuracy of future projections of extreme precipitation events.
• Continued exploration of the mechanisms driving changes in extreme rainfall, with a focus on the climate drivers and the regional atmospheric circulation changes.
• Enhanced dissemination of research findings to the wider public, facilitating informed decision-making and adaptation efforts.
Potential impacts of the project include:
• Improved understanding of extreme precipitation events can help policymakers and climate-related risk assessment agencies develop more effective strategies for mitigating the impacts of extreme precipitation events.
• By contributing to our understanding of climate change and its impacts on extreme precipitation events, the project has broader implications for society, including raising awareness of climate-related risks.
Expected results following UMBRELLE achievements include:
• Further refinement of climate modeling techniques to improve the accuracy of future projections of extreme precipitation events.
• Continued exploration of the mechanisms driving changes in extreme rainfall, with a focus on the climate drivers and the regional atmospheric circulation changes.
• Enhanced dissemination of research findings to the wider public, facilitating informed decision-making and adaptation efforts.
Potential impacts of the project include:
• Improved understanding of extreme precipitation events can help policymakers and climate-related risk assessment agencies develop more effective strategies for mitigating the impacts of extreme precipitation events.
• By contributing to our understanding of climate change and its impacts on extreme precipitation events, the project has broader implications for society, including raising awareness of climate-related risks.