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In January 2016, an extratropical low-pressure system that formed over the western North Atlantic basin, underwent tropical transition after moving to the eastern basin, becoming Hurricane Alex, an extremely rare hurricane event and the first to form in January since 1938. We examine herein the factors affecting the transition of the extratropical cyclone into Hurricane Alex and the predictability of that evolution. 51 ensembles from the European Centre for Medium-Range Weather Forecasts Ensemble Prediction System (ECMWF-EPS) are grouped, using a regression mixture model, based on similarities related to the storm's path within its cyclone phase space, giving various possible scenarios of structural development. First results indicate synoptic differences between scenarios. Three of them are shown to be statistically significant different and meteorologically consistent, and are further investigated. It can be therefore analyzed these different developments of the cyclone continuing as an extratropical cyclone or transitioning into subtropical or tropical (as in the reality). To analyze mesoscale processes' role in each development, WRF model simulations are nested in those ensemble members which better represent each cluster composite. As a result, it is possible to shed light on the role of synoptic and meso- scale processes in promoting the tropical transition of Hurricane Alex, which demonstrates the potential use of this methodology to investigate cyclones' behavior. On the other hand, another important aim of this study is to analyze the performance of this technique when used to improve the complex forecasting issue of the development of an extratropical cyclone into hurricane while embedded in the midlatitude atmospheric flow.

Cyclones with tropical characteristics are rare in the Mediterranean Sea, because atmospheric and oceanic conditions are unfavourable for their development and maintenance. In the Mediterranean Sea, this type of cyclones are called Medicanes (“Mediterranean Hurricanes”). In recent years, some intense Medicanes have been observed such as the medicaneof November 2011 [1]. Medicanes are associated with phenomena like heavy winds, rain, and storm surge, which affect specially coast areas. The main aim of this work is the study of future projections for these type of cyclones in the Mediter- ranean basin with climate regional models, analysing the effect of the atmosphere-ocean coupling and high resolution. The analysis is realized for the future climate scenario RCP85 until 2100. The simulations were done in the framework of European projects MedCORDEX y EuroCORDEX. The analysis procedure includes the detection of cyclones with a method adapted for mesoscale cyclones [2] and the application of Hart method [3] for analysing the structure of the cyclones and detecting tropical characteristic. The first results of this study show a greater frequency and intensity of Medicanes in higher resolution models compared to lower resolution ones, in agreement with previous results [4]. Also, a decrease of Mediter- ranean cyclones towards the end of the twenty-first century is generally found. The comparison of an air-sea coupled simulation with an uncoupled simulation shows interesting results: for present climate conditions, a higher medicane frequency is found in the uncoupled simulation, but during the last decades of present century more medicanes are detected in the coupled run. The projected future medicane decrease is therefore much smaller in the coupled run, pointing to complex and time-varying effects of air-sea coupling on this type of extreme phenomena.

The evolution of different renewable energy resources under different climate change scenarios is a key factor for the energy industry and for the energy transition. The possible changes with respect to present conditions for the operating plants and the projected resources can affect the financial frame and viability of the projects. Over Europe, climate models give a robust answer in terms of global warming and other important climate variables. However, GCMs and RCMs disagree in the projected changes of surface solar radiation (SSR) over Europe. Whereas global climate models, GCMs, present a clear positive signal for the end of XXI century, some studies show a negative anomaly for the same period in RCMs from EURO-CORDEX ensemble. This discrepancy is of special interest for photovoltaic (PV) power plants, whose resource is precisely solar radiation reaching earth’s surface. In this work, which is a contribution to the CORDEX FPS-aerosols, we try to explain the reasons of the difference in anomalies focusing on the representation of aerosols in the scenario simulations of RCMs. We use regional climate models simulations from the EURO-CORDEX ensemble grouped together by its forcing GCM. Different families of runs are analysed with only one simulation with evolving aerosols per group. We focus on RCP8.5 emissions scenario. In addition, a detailed PV model is used to estimate future PV potential over Europe, which has not been considered in previous approaches. Results of this study will lead to the obtention of more accurate PV projections over Europe, demanded by policymakers and the energy sector.

Medicanes are cyclones over the Mediterranean Sea having a tropical structure and a rather small size, for which the sea-atmosphere interaction plays a fundamental role. High resolution and ocean-atmosphere coupled RCM simulations performed in MedCORDEX and EURO-CORDEX projects are used to analyze the ability of RCMs to represent the observed characteristics of medicanes, and the impact of increasing resolution and using air-sea coupling on its simulation. An observational database based on satellite images combined with very high resolution simulations (Miglietta et al. 2013) is used as the reference for evaluating the simulations. The simulated medicanes do not coincide in general with the observed cases, so that the evaluation should be done in a statistical sense. The spatial distribution of medicanes is generally well simulated, while the monthly distribution reveals the difficulty of simulating the first medicanes appearing in September after the summer minimum. Large differences are found among models, supporting the use of multi-model ensembles. Interesting trade-offs are found for some models, as better values for intensity are associated to worse frequency values in one model, or relatively good values of frequency and intensity are obtained at the expense of a damped air-sea interaction in a model with spectral nudging. High resolution has a strong and positive impact on the frequency of simulated medicanes, while the effect on its intensity is less clear. Air-sea coupling reduces the medicane frequency, as could be expected due to a negative intensity feedback that is known for tropical cyclones. A preliminary analysis indicates that this feedback could depend on the oceanic mixed layer depth, increasing the interest of applying ocean-atmosphere coupled RCMs.

International audience; In the framework of the international initiative Coordinated Regional Downscaling Experiment (CORDEX) program, new regional climate model (RCM) simulations at high spatial resolutions are completed for the Mediterranean region (Med-CORDEX). This study evaluates the most up-to-date high-resolution simulations for hydrological impact studies over a catchment located in North Morocco. Different approaches are compared to analyze the climate change impacts on the hydrology of this catchment, using RCMs from the Med-CORDEX initiative at two different spatial resolutions (50 and 12 km) and for two different Radiative Concentration Pathways (RCP4.5 and RCP8.5). The main issues addressed in the present study are: (i) what is the impact of increased RCM resolution on present-climate hydrological simulations and on future projections? (ii) Are the bias-correction for the RCM outputs and the parameters of the hydrological model stationary and transferable to different climatic conditions? (iii) What is the climate and hydrological change signal based on the new scenarios (RCP4.5 and RCP8.5)? Results indicate that high resolution simulations at 12 km better reproduce the seasonal patterns, the seasonal distributions of precipitation and the extreme precipitation events. The parameters of the hydrological model, calibrated to reproduce runoff at the monthly time step over the time period 1984-2010, do not show a strong variability between dry and wet calibration periods in a differential split-sample test. However the bias correction of precipitation by quantile-matching does not give satisfactory results in validation using the same differential split-sample testing method. Therefore a quantile-perturbation method that does not rely on any stationarity assumption and produces ensembles of perturbed series of precipitation was introduced. The climate change signal under RCP4.5 and RCP8.5 forcings indicates a decrease in between -30 to -57% in surface runoff for the mid-term (2041-2062) with the different models, when for the same period the projections for precipitation are ranging between -15 and -24% and for temperature between + 1.3 and + 2.3 degrees C.

Mediterranean hurricanes (Medicanes) are mesoscale intense cyclones that acquire tropical characteristics. As they are often associated with extreme winds and rainfall, Medicanes pose a serious natural hazard to populated areas along Mediterranean coasts. Understanding how Medicanes will change with global warming remains, however, a challenge, because coarse resolution and the lack of atmosphere-ocean coupling limit the reliability of numerical simulation in global and regional models, respectively. Here we investigate the Medicanes' response to the intermediate 21st century emission scenario RCP4.5 using a recently developed 25-km global coupled climate model which features a realistic representation of Medicanes in present climate conditions. It is found that despite a decrease in the mean number of Medicanes, they potentially become more hazardous in the late century. They tend to last longer and to produce stronger wind, with a more robust hurricane-like structure. These changes are mainly confined to autumn. Increase in Medicane tropical nature is also accompanied by increasing rainfall. Thus, continued anthropogenic warming will increase the risks associated with Medicanes even in an intermediate scenario, with potential natural and socio-economic consequences.

Cyclones with tropical characteristics are rare in the Mediterranean Sea, because atmospheric and oceanic conditions are unfavourable for their development and maintenance. In the Mediterranean Sea, this type of cyclones are called Medicanes (“Mediterranean Hurricanes”). In recent years, some intense Medicanes have been observed such as the medicaneof November 2011 [1]. Medicanes are associated with phenomena like heavy winds, rain, and storm surge, which affect specially coast areas. The main aim of this work is the study of future projections for these type of cyclones in the Mediter- ranean basin with climate regional models, analysing the effect of the atmosphere-ocean coupling and high resolution. The analysis is realized for the future climate scenario RCP85 until 2100. The simulations were done in the framework of European projects MedCORDEX y EuroCORDEX. The analysis procedure includes the detection of cyclones with a method adapted for mesoscale cyclones [2] and the application of Hart method [3] for analysing the structure of the cyclones and detecting tropical characteristic. The first results of this study show a greater frequency and intensity of Medicanes in higher resolution models compared to lower resolution ones, in agreement with previous results [4]. Also, a decrease of Mediter- ranean cyclones towards the end of the twenty-first century is generally found. The comparison of an air-sea coupled simulation with an uncoupled simulation shows interesting results: for present climate conditions, a higher medicane frequency is found in the uncoupled simulation, but during the last decades of present century more medicanes are detected in the coupled run. The projected future medicane decrease is therefore much smaller in the coupled run, pointing to complex and time-varying effects of air-sea coupling on this type of extreme phenomena.

The evolution of different renewable energy resources under different climate change scenarios is a key factor for the energy industry and for the energy transition. The possible changes with respect to present conditions for the operating plants and the projected resources can affect the financial frame and viability of the projects. Over Europe, climate models give a robust answer in terms of global warming and other important climate variables. However, GCMs and RCMs disagree in the projected changes of surface solar radiation (SSR) over Europe. Whereas global climate models, GCMs, present a clear positive signal for the end of XXI century, some studies show a negative anomaly for the same period in RCMs from EURO-CORDEX ensemble. This discrepancy is of special interest for photovoltaic (PV) power plants, whose resource is precisely solar radiation reaching earth’s surface. In this work, which is a contribution to the CORDEX FPS-aerosols, we try to explain the reasons of the difference in anomalies focusing on the representation of aerosols in the scenario simulations of RCMs. We use regional climate models simulations from the EURO-CORDEX ensemble grouped together by its forcing GCM. Different families of runs are analysed with only one simulation with evolving aerosols per group. We focus on RCP8.5 emissions scenario. In addition, a detailed PV model is used to estimate future PV potential over Europe, which has not been considered in previous approaches. Results of this study will lead to the obtention of more accurate PV projections over Europe, demanded by policymakers and the energy sector.

The evolution of different renewable energy resources under different climate change scenarios is a key factor for the energy industry and for the energy transition. The possible changes with respect to present conditions for the operating plants and the projected resources can affect the financial frame and viability of the projects.Over Europe, climate models give a robust answer in terms of global warming and other important climate variables. However, GCMs and RCMs disagree in the projected changes of surface solar radiation (SSR) over Europe. Whereas global climate models, GCMs, present a clear positive signal for the end of XXI century, some studies show a negative anomaly for the same period in RCMs from EURO-CORDEX ensemble. This discrepancy is of special interest for photovoltaic (PV) power plants, whose resource is precisely solar radiation reaching earth's surface.In this work, which is a contribution to the CORDEX FPS-aerosols, we try to explain the reasons of the difference in anomalies focusing on the representation of aerosols in the scenario simulations of RCMs. We use regional climate models simulations from the EURO-CORDEX ensemble grouped together by its forcing GCM. Different families of runs are analysed with only one simulation with evolving aerosols per group. We focus on RCP8.5 emissions scenario. In addition, a detailed PV model is used to estimate future PV potential over Europe, which has not been considered in previous approaches.Results of this study will lead to the obtention of more accurate PV projections over Europe, demanded by policymakers and the energy sector.

In this report a set of indicators is proposed for summarizing objectives and providing up-to-date information on the impacts of climate change, the state-of-the-environment and societal conditions of islands. These indicators are meant to support a practical description. They can be used for identifying policy goals, defining strategies, monitoring and evaluating implemented actions. They are also useful for communicating the environmental and societal conditions to a particular audience, such as local stakeholders, administrations, general public, policymakers from local to national levels. Finally, they provide a synthetic way to describe multiple aspects of the state of environment, natural resources assets and related human activities including socio-economic factors. These indicators are based on environmental data, models, oceanographic and meteorological observations, and administrative archives. They are based on several parameters including physical, chemical or biological measures associated with environmental quality or natural resources, information on processes and interventions, economical values, members describing the composition and characteristics of societies and of their needs. The indicators are focused on the four sectors addressed by SOCLIMPACT and strictly linked to the identified impact chains. They allow:  To compare conditions among islands  To identify critical situations  To identify trends and evolution of conditions leading to risks  To monitor risks  To monitor the results of management strategies, Deliverable 3.3.

In January 2016, an extratropical low-pressure system that formed over the western North Atlantic basin, underwent tropical transition after moving to the eastern basin, becoming Hurricane Alex, an extremely rare hurricane event and the first to form in January since 1938. We examine herein the factors affecting the transition of the extratropical cyclone into Hurricane Alex and the predictability of that evolution. 51 ensembles from the European Centre for Medium-Range Weather Forecasts Ensemble Prediction System (ECMWF-EPS) are grouped, using a regression mixture model, based on similarities related to the storm's path within its cyclone phase space, giving various possible scenarios of structural development. First results indicate synoptic differences between scenarios. Three of them are shown to be statistically significant different and meteorologically consistent, and are further investigated. It can be therefore analyzed these different developments of the cyclone continuing as an extratropical cyclone or transitioning into subtropical or tropical (as in the reality). To analyze mesoscale processes' role in each development, WRF model simulations are nested in those ensemble members which better represent each cluster composite. As a result, it is possible to shed light on the role of synoptic and meso- scale processes in promoting the tropical transition of Hurricane Alex, which demonstrates the potential use of this methodology to investigate cyclones' behavior. On the other hand, another important aim of this study is to analyze the performance of this technique when used to improve the complex forecasting issue of the development of an extratropical cyclone into hurricane while embedded in the midlatitude atmospheric flow.

Presentation at SOCLIMPACT webinar on 02/09/2020 to the online community Main topics: Operationalization - Energy ICs (method enhancements) Operationalization - Energy ICs (Selection of ICs and islands) Impact Chain: Risk of changes in energy demand due to changes in temperature and precipitation Weights for desalination demand IC Risk scores for desalination demand IC Risk scores for cooling demand IC Assessment of energy IC operationalization

This study aims to assess the skill of regional climate models (RCMs) at reproducing the climatology of Mediterranean cyclones. Seven RCMs are considered, five of which were also coupled with an oceanic model. All simulations were forced at the lateral boundaries by the ERA-Interim reanalysis for a common 20-year period (1989–2008). Six different cyclone tracking methods have been applied to all twelve RCM simulations and to the ERA-Interim reanalysis in order to assess the RCMs from the perspective of different cyclone definitions. All RCMs reproduce the main areas of high cyclone occurrence in the region south of the Alps, in the Adriatic, Ionian and Aegean Seas, as well as in the areas close to Cyprus and to Atlas mountains. The RCMs tend to underestimate intense cyclone occurrences over the Mediterranean Sea and reproduce 24–40 % of these systems, as identified in the reanalysis. The use of grid nudging in one of the RCMs is shown to be beneficial, reproducing about 60 % of the intense cyclones and keeping a better track of the seasonal cycle of intense cyclogenesis. Finally, the most intense cyclones tend to be similarly reproduced in coupled and uncoupled model simulations, suggesting that modeling atmosphere–ocean coupled processes has only a weak impact on the climatology and intensity of Mediterranean cyclones. This paper is a contribution to the special issue on Med-CORDEX, an international coordinated initiative dedicated to the multi-component regional climate modelling (atmosphere, ocean, land surface, river) of the Mediterranean under the umbrella of HyMeX, CORDEX, and Med-CLIVAR and coordinated by Samuel Somot, Paolo Ruti, Erika Coppola, Gianmaria Sannino, Bodo Ahrens, and Gabriel Jordà.