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Surface air Temperature variations (DT) on the short time scale (from 1 to 7/15/30 days), defined as the difference of daily temperature between one day and a next one, can have strong impacts on human health and plant development. This analysis investigates EURO-CORDEX Regional Climate Model simulations data, at the highest horizontal resolution available (EUR-11 domain: about 11 km) collected within the EU H2020 project COACCH. The Mediterranean regions appears as the most prone to DT increase, in a warmer climate, within the European domain. Based on a multi-model multi-scenario approach we aim to quantify such changes and the related uncertainty within the current century. Changes in the length of the seasons are also inspected to verify potential linkages to the DT changes. The model validation is based on JRA-55 reanalysis covering the 1985-2015 period. Future tendencies of the aforementioned parameter are inspected following three Representative Concentration Pathways (RCPs) taking part to the fifth Coupled Model Intercomparison Project (CMIP5): RCP2.6, RCP4.5 and RCP8.5. A comparison of the results obtained based on bias corrected and raw temperature data is provided and discussed.The Keywords: Temperature, Europe, Future Scenarios, CORDEX [ABSTRACT FROM AUTHOR]

Groundwater is the primary source of water supply for sustaining the lives of billion ofpeople and surrounding ecosystems around the Globe. Climate change and variabilitythreaten the sustainable use of renewable groundwater resources in many regions across theWorld. Yet the assessment on the effects of global warming on projected estimates ofrenewable groundwater resources and uncertainties surrounding those estimates at alocally relevant scale is lacking. Here, we provide a comprehensive, continental-scaleassessment of past, present, and future changes in renewable groundwater resources(as a form of groundwater recharge after being suitably aggregated to longer timescales) across Europe at an unprecedented spatial resolution of (5 X 5) km2 andlocal groundwater bodies as per the European Water Framework Directive (WFD).Specifically our aim here is to understand the response of Europe-wide groundwaterresources to different global warming levels in accordance to 2015 IPCC Parisagreement. Our analyses are based on multi-model ensemble simulations from theEDgE1 and HOKLIM2 projects (funded by ECMWF and BMBF-Germany) whichcomprises of four hydrologic and land-surface models (HMs: mHM, Noah-MP,PCR-GLOBWB, and VIC) driven by a suitably downscaled, observation basedE-OBS forcing data for the historical records (1950-2015) and five bias correctedCMIP5 GCMs datasets for the near-past to future climate conditions (1970-2100)under three representative concentration pathways (RCPs: 2.6, 6.0, and 8.5). Atime-sampling approach is applied to identify 30-year periods with distinct warming levelscorresponding to global surface air temperature increase of 1.5, 2.0, and 3.0 K compared tothe pre-industrial levels. We contrast the changes in the multi-model ensemblerecharge between the periods of distinct warming levels and to the contemporaryconditions (1971-2000). Our analyses show a clear North-South gradient of changes inmean annual recharge across Europe with declining trends being observed in theMediterranean region, and increased availability of groundwater resources in theNorth Scandinavian region with increased warming (at end of the Century). Thecontinental part of the Europe shows relatively lower changes in the mean renewablegroundwater resources. A greater sensitivity/amplifications in changes are noticed in theMediterranean region to the response of increased warming levels. Though limited, but ourensemble simulations allow disentangling the different sources of uncertainties(HMs vs. GCMs) – which generally pointed out a larger chunk of uncertainty inmodeling results arises due to differences among GCMs (forcings); but there are clearlyareas where the uncertainty due to (different process representation of) HMs issubstantial, and can not be neglected. Overall, our study underscores the need formulti-model ensembles for the assessment of future changes in renewable groundwaterresources across Europe, and discuss about related impacts avoided in higher warmingworlds. 1. www.edge.climate.copernicus.eu 2. www.ufz.de/hoklim [ABSTRACT FROM AUTHOR]

Climate change is expected to affect substantially future water availability and temperature across many watersheds in Europe potentially impacting hydropower generation and cooling efficiency of thermo-nuclear power plants. On the other hand, increasing Renewable Energy Sources (RES) penetration will substantially modify energy portfolios across Europe. As a consequence, prices will become more volatile, requiring more system flexibility. This study aims to explore the following key questions for supporting the definition and implementation of EU transition policies driving investments in the energy sector: 1) How climate change impacts on the hydrological system propagate to the energy system? 2) Can hydropower provide additional flexibility to a high RES-based energy system? To answer these questions, we developed an integrated modelling approaches combining a conceptual hydrological model (HBV) and an energy system model (PRIMES-IEM). Based on daily air temperature and precipitation, HBV computes daily streamflow for each power plant. Water temperature is obtained from air temperature using an empirical formula. These two variables are used to define the constraints to the energy model PRIMES-IEM, a power market simulator of the European electricity markets.Our analysis focuses on Iberian Peninsula and Danube region in 2040. Both regions' energy mix have a significant share of hydropower and rely significantly on thermo-nuclear power plants. In addition, both systems have already been under stress conditions due to heatwaves and droughts over the last years. On the climate side, we downscaled projected air temperature and precipitation projections for the RCP2.6 and RCP8.5 scenarios, covering the full range of possible climate futures from very low emission pathways to very high ones. On the energy side, we also consider two scenarios representative of the current system and of a future decarbonized system complying with European climate targets at 2030 and 2050. Despite some differences across the two regions, numerical results suggest some general trends: hot and dry climate futures significantly impact on the energy system because either increasing water temperature produces heavy stress due to thermonuclear generation curtailment or declining water availability limits hydropower generation forcing the energy system to shift to other technologies in order to maintain its reliability. [ABSTRACT FROM AUTHOR]

The extratropical cyclone is one of the basic systems that characterize the weather and climate in mid-latitude areas, where the mean meridional temperature gradient is large. As for in Europe's middle or higher latitude areas. Although the climatological mean meridional gradient of the air temperature there is rather weak compared to that from autumn to spring around Japan in East Asia, many extratropical cyclones appear throughout a year. Thus it would still be necessary to re-examine the seasonal cycle of the daily cyclone and anticyclone activities around Europe, paying attention also to their intraseasonal variations and the effects on the behaviors of daily cyclone and anticyclone systems together with the variety of their characteristics. Our previous case studies for 2000 (Kuwana et al., EGU2017 and 2018) pointed out that daily cyclones and anticyclones were greatly reflected by the alternation of the intraseasonal-scale ones with equivalent barotropic structure in northwestern Europe in summer. In addition, the intraseasonal and daily behaviors of the Icelandic low in the seasonal cycle showed the seasonal progression from autumn to the next spring.The present study will further examine the detailed features on the above mentioned topics, together with their relationship to the weather conditions in Europe, mainly based on the NCEP/NCAR re-analysis data. From late May to August, intraseasonal-scale low and high areas (as for the deviation fields) with the equivalent barotropic structure extended from the Norwegian Sea to Northern Germany. In the negative deviation period (stage with the intraseasonal-scale low there), baroclinic zone in the lower layer just on the south of that low was periodically enhanced. It is interesting that, in one of the negative periods, the southward shift of intraseasonal-scale baroclinic zone seemed to be related to the temporal activity of baroclinic ibstability wave cyclones, or the rather lower air temperature stage in central Europe. The detailed description on there will be made at the poster presentation. As for the asymmetric seasonal progression, not only the differences of intraseasonal features of the Icelandic lows between the former half and latter half of winter as shown in EGU2018, but also the differences of the daily variations between early summer and early autumn were notable. As for early autumn, amplitude of the short-period SLP variation in northern Europe, corresponding to the temporal appearance of the "Icelandic low-like" cyclone with relatively short persistency, increased greatly one month earlier than the formation timing of the seasonal mean Icelandic low in middle October. Interestingly, that event occurred just when the air temperature began to decrease seasonally. [ABSTRACT FROM AUTHOR]