Michele Bendoni

This study presents an integrated modeling framework designed to bridge scales from regional to urban, enabling a detailed assessment of the impacts of future climate scenarios on three European coastal cities: Massa (Italy) and Vilanova (Spain) in the Mediterranean, and Oarsoaldea (Spain) in the Atlantic. Conducted as part of the SCORE EU Project (Smart Control of Climate Resilience in European Coastal Cities), the framework employs a novel, non-standard downscaling approach to translate large-scale atmospheric outputs from the EURO-CORDEX regional model ALADIN63 (for Historical, RCP4.5, and RCP8.5 scenarios) into high-resolution simulations of storm surges, wave climate, and river discharge using SHYFEM, WAVEWATCH III, and LISFLOOD models. The framework achieves coastal resolutions on the order of 100 m, providing time series of water levels and wave runup, which are combined into total water levels. These results, together with extreme value analysis of river discharge and projected relative sea level rise (RSLR), are used as boundary conditions for an urban-scale hydrodynamic model with resolutions as fine as 2–20 m. This multi-scale integration allows for detailed analysis of changes in flooded areas and volumes under RCP4.5 and RCP8.5 scenarios, relative to historical conditions, highlighting the influence of shifting extremes, RSLR, and site-specific features. Results show that in Massa and Vilanova, increased extreme river discharges are projected, while moderate changes in extreme water levels are overshadowed by RSLR, particularly for Massa. Oarsoaldea, well protected from storm surges, is expected to experience a slight reduction in extreme river discharge. This work demonstrates the capability of an integrated modeling framework to address climate change impacts at the urban scale. Local-scale modeling is essential: accurate flood hazard assessment in coastal cities requires high-resolution simulations to capture the influence of local topography and infrastructure, especially where global DEMs are inadequate. By linking climate projections to urban flood impacts, the framework enables a consistent evaluation of future extremes, sea level rise, and their interaction. A further key message of this study is the need to generate actionable insights to support the development of targeted and site-specific adaptation strategies. Adaptation must be tailored: only by quantifying future extremes and exposure is it possible to design effective, place-based responses.

We present a 4D-Var data assimilation (DA) system covering the North-Western Mediterranean Sea implemented with the Regional Ocean Modeling System (ROMS). We study, throughout the year 2022, its ability to improve the description of the overall circulation and the capability to constrain the transport across the Corsica Channel (CC), the dynamics of which are crucial in determining the circulation throughout the region. The system assimilates Sea Surface Temperature (SST) and Sea Level Anomaly (SLA) observations from satellites, surface velocity data from High-Frequency Radars (HFRs), and in situ temperature, salinity and velocity observations, the latter from a mooring located in the CC. For all the observed state variables, DA is able to improve the forecast and the analysis compared to a free run without DA, with root mean squared error reduction up to 60 % and correlation increase up to 0.4. The general circulation after DA is characterized by a reduction of the Eastern Corsica Current (ECC) and an increase of the Western Corsica Current (WCC). An adjoint sensitivity-based method was used to evaluate the impact of observations on the CC transport state estimates. The net reduction in transport induced by DA, changed the annual average value of 0.49 Sv for the free run, to 0.31 and 0.28 Sv for the forecast and analysis, respectively. The observations that contribute most to the transport changes are the in situ velocity data and those from HFRs. The observation impacts were found to vary seasonally, and sometimes act in competition to shape the circulation pathways across the CC. The sensitivity of the transport to SST and in situ temperature and salinity observations indicates that remote measurements (e.g. those from the Gulf of Lion) can potentially play a significant role in constraining the CC transport. Transport variations are largely affected by free surface gradients contained in the increment, and promoted by modifications to the open boundary conditions. This indicates that the CC dynamic is controlled by mechanisms operating at basin scales.

We present a 4D-Var data assimilation (DA) system covering the North-Western Mediterranean Sea implemented with the Regional Ocean Modeling System (ROMS). We study, throughout the year 2022, its ability to improve the description of the overall circulation and the capability to constrain the transport across the Corsica Channel (CC), the dynamics of which are crucial in determining the circulation throughout the region. The system assimilates Sea Surface Temperature (SST) and Sea Level Anomaly (SLA) observations from satellites, surface velocity data from High-Frequency Radars (HFRs), and in situ temperature, salinity and velocity observations, the latter from a mooring located in the CC. For all the observed state variables, DA is able to improve the forecast and the analysis compared to a free run without DA, with root mean squared error reduction up to 60 % and correlation increase up to 0.4. The general circulation after DA is characterized by a reduction of the Eastern Corsica Current (ECC) and an increase of the Western Corsica Current (WCC). An adjoint sensitivity-based method was used to evaluate the impact of observations on the CC transport state estimates. The net reduction in transport induced by DA, changed the annual average value of 0.49 Sv for the free run, to 0.31 Sv and 0.28 Sv for the forecast and analysis, respectively. The observations that contribute most to the transport changes are the in situ velocity data and those from HFRs. The observation impacts were found to vary seasonally, and sometimes act in competition to shape the circulation pathways across the CC. The sensitivity of the transport to SST and in situ temperature and salinity observations indicates that remote measurements (e.g. those from the Gulf of Lion) can potentially play a significant role in constraining the CC transport. Transport variations are largely affected by free surface gradients contained in the increment, and promoted by modifications to the open boundary conditions. This indicates that the CC dynamic is controlled by mechanisms operating at basin scales.

We present a 4D-Var data assimilation (DA) system covering the North-Western Mediterranean Sea implemented with the Regional Ocean Modeling System (ROMS). We study, throughout the year 2022, its ability to improve the description of the overall circulation and the capability to constrain the transport across the Corsica Channel (CC), the dynamics of which are crucial in determining the circulation throughout the region. The system assimilates Sea Surface Temperature (SST) and Sea Level Anomaly (SLA) observations from satellites, surface velocity data from High-Frequency Radars (HFRs), and in situ temperature, salinity and velocity observations, the latter from a mooring located in the CC. For all the observed state variables, DA is able to improve the forecast and the analysis compared to a free run without DA, with root mean squared error reduction up to 60 % and correlation increase up to 0.4. The general circulation after DA is characterized by a reduction of the Eastern Corsica Current (ECC) and an increase of the Western Corsica Current (WCC). An adjoint sensitivity-based method was used to evaluate the impact of observations on the CC transport state estimates. The net reduction in transport induced by DA, changed the annual average value of 0.49 Sv for the free run, to 0.31 Sv and 0.28 Sv for the forecast and analysis, respectively. The observations that contribute most to the transport changes are the in situ velocity data and those from HFRs. The observation impacts were found to vary seasonally, and sometimes act in competition to shape the circulation pathways across the CC. The sensitivity of the transport to SST and in situ temperature and salinity observations indicates that remote measurements (e.g. those from the Gulf of Lion) can potentially play a significant role in constraining the CC transport. Transport variations are largely affected by free surface gradients contained in the increment, and promoted by modifications to the open boundary conditions. This indicates that the CC dynamic is controlled by mechanisms operating at basin scales.

We present a 4D-Var data assimilation (DA) system covering the North-Western Mediterranean Sea implemented with the Regional Ocean Modeling System (ROMS). We study, throughout the year 2022, its ability to improve the description of the overall circulation and the capability to constrain the transport across the Corsica Channel (CC), the dynamics of which are crucial in determining the circulation throughout the region. The system assimilates Sea Surface Temperature (SST) and Sea Level Anomaly (SLA) observations from satellites, surface velocity data from High-Frequency Radars (HFRs), and in situ temperature, salinity and velocity observations, the latter from a mooring located in the CC. For all the observed state variables, DA is able to improve the forecast and the analysis compared to a free run without DA, with root mean squared error reduction up to 60 % and correlation increase up to 0.4. The general circulation after DA is characterized by a reduction of the Eastern Corsica Current (ECC) and an increase of the Western Corsica Current (WCC). An adjoint sensitivity-based method was used to evaluate the impact of observations on the CC transport state estimates. The net reduction in transport induced by DA, changed the annual average value of 0.49 Sv for the free run, to 0.31 Sv and 0.28 Sv for the forecast and analysis, respectively. The observations that contribute most to the transport changes are the in situ velocity data and those from HFRs. The observation impacts were found to vary seasonally, and sometimes act in competition to shape the circulation pathways across the CC. The sensitivity of the transport to SST and in situ temperature and salinity observations indicates that remote measurements (e.g. those from the Gulf of Lion) can potentially play a significant role in constraining the CC transport. Transport variations are largely affected by free surface gradients contained in the increment, and promoted by modifications to the open boundary conditions. This indicates that the CC dynamic is controlled by mechanisms operating at basin scales.

We present a 4D-Var data assimilation (DA) system covering the North-Western Mediterranean Sea implemented with the Regional Ocean Modeling System (ROMS). We study, throughout the year 2022, its ability to improve the description of the overall circulation and the capability to constrain the transport across the Corsica Channel (CC), the dynamics of which are crucial in determining the circulation throughout the region. The system assimilates Sea Surface Temperature (SST) and Sea Level Anomaly (SLA) observations from satellites, surface velocity data from High-Frequency Radars (HFRs), and in situ temperature, salinity and velocity observations, the latter from a mooring located in the CC. For all the observed state variables, DA is able to improve the forecast and the analysis compared to a free run without DA, with root mean squared error reduction up to 60 % and correlation increase up to 0.4. The general circulation after DA is characterized by a reduction of the Eastern Corsica Current (ECC) and an increase of the Western Corsica Current (WCC). An adjoint sensitivity-based method was used to evaluate the impact of observations on the CC transport state estimates. The net reduction in transport induced by DA, changed the annual average value of 0.49 Sv for the free run, to 0.31 Sv and 0.28 Sv for the forecast and analysis, respectively. The observations that contribute most to the transport changes are the in situ velocity data and those from HFRs. The observation impacts were found to vary seasonally, and sometimes act in competition to shape the circulation pathways across the CC. The sensitivity of the transport to SST and in situ temperature and salinity observations indicates that remote measurements (e.g. those from the Gulf of Lion) can potentially play a significant role in constraining the CC transport. Transport variations are largely affected by free surface gradients contained in the increment, and promoted by modifications to the open boundary conditions. This indicates that the CC dynamic is controlled by mechanisms operating at basin scales.

We present a 4D-Var data assimilation (DA) system covering the North-Western Mediterranean Sea implemented with the Regional Ocean Modeling System (ROMS). We study, throughout the year 2022, its ability to improve the description of the overall circulation and the capability to constrain the transport across the Corsica Channel (CC), the dynamics of which are crucial in determining the circulation throughout the region. The system assimilates Sea Surface Temperature (SST) and Sea Level Anomaly (SLA) observations from satellites, surface velocity data from High-Frequency Radars (HFRs), and in situ temperature, salinity and velocity observations, the latter from a mooring located in the CC. For all the observed state variables, DA is able to improve the forecast and the analysis compared to a free run without DA, with root mean squared error reduction up to 60 % and correlation increase up to 0.4. The general circulation after DA is characterized by a reduction of the Eastern Corsica Current (ECC) and an increase of the Western Corsica Current (WCC). An adjoint sensitivity-based method was used to evaluate the impact of observations on the CC transport state estimates. The net reduction in transport induced by DA, changed the annual average value of 0.49 Sv for the free run, to 0.31 Sv and 0.28 Sv for the forecast and analysis, respectively. The observations that contribute most to the transport changes are the in situ velocity data and those from HFRs. The observation impacts were found to vary seasonally, and sometimes act in competition to shape the circulation pathways across the CC. The sensitivity of the transport to SST and in situ temperature and salinity observations indicates that remote measurements (e.g. those from the Gulf of Lion) can potentially play a significant role in constraining the CC transport. Transport variations are largely affected by free surface gradients contained in the increment, and promoted by modifications to the open boundary conditions. This indicates that the CC dynamic is controlled by mechanisms operating at basin scales.

This study presents an integrated modeling framework designed to bridge scales from regional to urban, enabling a detailed assessment of the impacts of future climate scenarios on three European coastal cities: Massa (Italy) and Vilanova (Spain) in the Mediterranean, and Oarsoaldea (Spain) in the Atlantic. Conducted as part of the SCORE EU Project (Smart Control of Climate Resilience in European Coastal Cities), the framework employs a novel, non-standard downscaling approach to translate large-scale atmospheric outputs from the EURO-CORDEX regional model ALADIN63 (for Historical, RCP4.5, and RCP8.5 scenarios) into high-resolution simulations of storm surges, wave climate, and river discharge using SHYFEM, WAVEWATCH III, and LISFLOOD models. The framework achieves coastal resolutions on the order of 100 m, providing time series of water levels and wave runup, which are combined into total water levels. These results, together with extreme value analysis of river discharge and projected relative sea level rise (RSLR), are used as boundary conditions for an urban-scale hydrodynamic model with resolutions as fine as 2–20 m. This multi-scale integration allows for detailed analysis of changes in flooded areas and volumes under RCP4.5 and RCP8.5 scenarios, relative to historical conditions, highlighting the influence of shifting extremes, RSLR, and site-specific features. Results show that in Massa and Vilanova, increased extreme river discharges are projected, while moderate changes in extreme water levels are overshadowed by RSLR, particularly for Massa. Oarsoaldea, well protected from storm surges, is expected to experience a slight reduction in extreme river discharge. This work demonstrates the capability of the integrated framework to address climate change impacts at urban scales, providing valuable insights for the development of localized adaptation strategies.

This study presents an integrated modeling framework designed to bridge scales from regional to urban, enabling a detailed assessment of the impacts of future climate scenarios on three European coastal cities: Massa (Italy) and Vilanova (Spain) in the Mediterranean, and Oarsoaldea (Spain) in the Atlantic. Conducted as part of the SCORE EU Project (Smart Control of Climate Resilience in European Coastal Cities), the framework employs a novel, non-standard downscaling approach to translate large-scale atmospheric outputs from the EURO-CORDEX regional model ALADIN63 (for Historical, RCP4.5, and RCP8.5 scenarios) into high-resolution simulations of storm surges, wave climate, and river discharge using SHYFEM, WAVEWATCH III, and LISFLOOD models. The framework achieves coastal resolutions on the order of 100 m, providing time series of water levels and wave runup, which are combined into total water levels. These results, together with extreme value analysis of river discharge and projected relative sea level rise (RSLR), are used as boundary conditions for an urban-scale hydrodynamic model with resolutions as fine as 2–20 m. This multi-scale integration allows for detailed analysis of changes in flooded areas and volumes under RCP4.5 and RCP8.5 scenarios, relative to historical conditions, highlighting the influence of shifting extremes, RSLR, and site-specific features. Results show that in Massa and Vilanova, increased extreme river discharges are projected, while moderate changes in extreme water levels are overshadowed by RSLR, particularly for Massa. Oarsoaldea, well protected from storm surges, is expected to experience a slight reduction in extreme river discharge. This work demonstrates the capability of the integrated framework to address climate change impacts at urban scales, providing valuable insights for the development of localized adaptation strategies.