@misc{CasanuevaKeulerKotlarskietal., author = {Casanueva, Anna and Keuler, Klaus and Kotlarski, Sven and Herrera, Sixto and Fern{\´a}ndez, J{\´e}sus and Guti{\´e}rrez, J. M. and Boberg, Fredrik and Colette, Augustin and B{\o}ssing Christensen, Ole and Goergen, Klaus and Jacob, Daniela and Nikulin, Grigory and Teichmann, Claas and Vautard, Robert}, title = {Daily precipitation statistics in a EURO-CORDEX RCM ensemble: Added value of raw and bias-corrected high-resolution simulations}, series = {Climate Dynamics}, volume = {47}, journal = {Climate Dynamics}, number = {3/4}, issn = {1432-0894}, doi = {10.1007/s00382-015-2865-x}, pages = {719 -- 737}, abstract = {Daily precipitation statistics as simulated by the ERA-Interim-driven EURO-CORDEX regional climate model (RCM) ensemble are evaluated over two distinct regions of the European continent, namely the European Alps and Spain. The potential added value of the high-resolution 12 km experiments with respect to their 50 km resolution counterparts is investigated. The statistics considered consist of wet-day intensity and precipitation frequency as a measure of mean precipitation, and three precipitation-derived indicators (90th percentile on wet days—90pWET, contribution of the very wet days to total precipitation—R95pTOT and number of consecutive dry days—CDD). As reference for model evaluation high resolution gridded observational data over continental Spain (Spain011/044) and the Alpine region (EURO4M-APGD) are used. The assessment and comparison of the two resolutions is accomplished not only on their original horizontal grids (approximately 12 and 50 km), but the high-resolution RCMs are additionally regridded onto the coarse 50 km grid by grid cell aggregation for the direct comparison with the low resolution simulations. The direct application of RCMs e.g. in many impact modelling studies is hampered by model biases. Therefore bias correction (BC) techniques are needed at both resolutions to ensure a better agreement between models and observations. In this work, the added value of the high resolution (before and after the bias correction) is assessed and the suitability of these BC methods is also discussed. Three basic BC methods are applied to isolate the effect of biases in mean precipitation, wet-day intensity and wet-day frequency on the derived indicators. Daily precipitation percentiles are strongly affected by biases in the wet-day intensity, whereas the dry spells are better represented when the simulated precipitation frequency is adjusted to the observed one. This confirms that there is no single optimal way to correct for RCM biases, since correcting some distributional features typically leads to an improvement of some aspects but to a deterioration of others. Regarding mean seasonal biases before the BC, we find only limited evidence for an added value of the higher resolution in the precipitation intensity and frequency or in the derived indicators. Thereby, evaluation results considerably depend on the RCM, season and indicator considered. High resolution simulations better reproduce the indicators' spatial patterns, especially in terms of spatial correlation. However, this improvement is not statistically significant after applying specific BC methods.}, language = {en} } @misc{PreinGobietTruhetzetal., author = {Prein, Andreas and Gobiet, Andreas and Truhetz, Heimo and Keuler, Klaus and Goergen, Klaus and Teichmann, Claas and Fox Maule, C. and Meijgaard, Erik van}, title = {Precipitation in the EURO-CORDEX 0.11° and 0.44° simulations: high resolution, high benefits?}, series = {Climate Dynamics}, volume = {46}, journal = {Climate Dynamics}, number = {1}, issn = {0930-7575}, doi = {10.1007/s00382-015-2589-y}, pages = {383 -- 412}, abstract = {In the framework of the EURO-CORDEX initiative an ensemble of European-wide high-resolution regional climate simulations on a 0.11∘(∼12.5km) grid has been generated. This study investigates whether the fine-gridded regional climate models are found to add value to the simulated mean and extreme daily and sub-daily precipitation compared to their coarser-gridded 0.44∘(∼50km) counterparts. Therefore, pairs of fine- and coarse-gridded simulations of eight reanalysis-driven models are compared to fine-gridded observations in the Alps, Germany, Sweden, Norway, France, the Carpathians, and Spain. A clear result is that the 0.11∘ simulations are found to better reproduce mean and extreme precipitation for almost all regions and seasons, even on the scale of the coarser-gridded simulations (50 km). This is primarily caused by the improved representation of orography in the 0.11∘ simulations and therefore largest improvements can be found in regions with substantial orographic features. Improvements in reproducing precipitation in the summer season appear also due to the fact that in the fine-gridded simulations the larger scales of convection are captured by the resolved-scale dynamics . The 0.11∘ simulations reduce biases in large areas of the investigated regions, have an improved representation of spatial precipitation patterns, and precipitation distributions are improved for daily and in particular for 3 hourly precipitation sums in Switzerland. When the evaluation is conducted on the fine (12.5 km) grid, the added value of the 0.11∘ models becomes even more obvious.}, language = {en} } @misc{BuelowHuebenerKeuleretal., author = {B{\"u}low, Katharina and H{\"u}bener, Heike and Keuler, Klaus and Menz, Christoph and Pfeifer, Susanne and Ramthun, Hans and Spekat, Arne and Steger, Christian and Teichmann, Claas and Warrach-Sagi, Kirsten}, title = {User tailored results of a regional climate model ensemble to plan adaption to the changing climate in Germany}, series = {Advances in Science and Research}, volume = {16}, journal = {Advances in Science and Research}, issn = {1992-0636}, doi = {10.5194/asr-16-241-2019}, pages = {241 -- 249}, abstract = {In the German regional climate modeling project ReKliEs-De the existing EURO-CORDEX simulations have been systematically complemented by new simulations to derive more robust ranges of possible future climate change. The focus of the project lay on user tailored results, which are required for the planning of measures to adapt to the changing climate. Changes in temperature and precipitation indices are calculated from a multi model ensemble for the end of the 21st century. The results for the mitigation scenario RCP2.6 are compared to the results of the "business as usual" scenario RCP8.5. Averaged over Germany the increase of mean annual temperature and of the number of summer days will be around 3 times higher for RCP8.5 than for RCP2.6. In summer, the increase of dry days could be twice as high in RCP8.5 compared to RCP2.6.}, language = {en} } @misc{JacobTeichmannKeuler, author = {Jacob, Daniela and Teichmann, Claas and Keuler, Klaus}, title = {Regional climate downscaling over Europe: perspectives from the EURO-CORDEX community}, series = {Regional Environmental Change}, volume = {20}, journal = {Regional Environmental Change}, issn = {1436-378X}, doi = {10.1007/s10113-020-01606-9}, pages = {20}, abstract = {The European CORDEX (EURO-CORDEX) initiative is a large voluntary effort that seeks to advance regional climate and Earth system science in Europe. As part of the World Climate Research Programme (WCRP) - Coordinated Regional Downscaling Experiment (CORDEX), it shares the broader goals of providing a model evaluation and climate projection framework and improving communication with both the General Circulation Model (GCM) and climate data user communities. EURO-CORDEX oversees the design and coordination of ongoing ensembles of regional climate projections of unprecedented size and resolution (0.11° EUR-11 and 0.44° EUR-44 domains). Additionally, the inclusion of empirical-statistical downscaling allows investigation of much larger multi-model ensembles. These complementary approaches provide a foundation for scientific studies within the climate research community and others. The value of the EURO-CORDEX ensemble is shown via numerous peer-reviewed studies and its use in the development of climate services. Evaluations of the EUR-44 and EUR-11 ensembles also show the benefits of higher resolution. However, significant challenges remain. To further advance scientific understanding, two flagship pilot studies (FPS) were initiated. The first investigates local-regional phenomena at convection-permitting scales over central Europe and the Mediterranean in collaboration with the Med-CORDEX community. The second investigates the impacts of land cover changes on European climate across spatial and temporal scales. Over the coming years, the EURO-CORDEX community looks forward to closer collaboration with other communities, new advances, supporting international initiatives such as the IPCC reports, and continuing to provide the basis for research on regional climate impacts and adaptation in Europe.}, language = {en} }