@misc{MohrKunzKeuler, author = {Mohr, Susanna and Kunz, Michael and Keuler, Klaus}, title = {Development and application of a logistic model to estimate the past and future hail potential in Germany}, series = {Journal of Geophysical Research: Atmospheres}, volume = {120}, journal = {Journal of Geophysical Research: Atmospheres}, number = {9}, issn = {2169-8996}, doi = {10.1002/2014JD022959}, pages = {3939 -- 3956}, abstract = {This study investigates to what extent the frequency of hail events in the summer months has changed during the past decades and which changes are expected to occur in the future. To improve the diagnostics of hail events by considering various factors relevant for the formation of hail, a logistic hail model has been developed by means of a multivariate analysis method. This statistical model is based on a combination of appropriate meteorological parameters (convective parameter, moisture content, etc.) and synoptic weather types. The output of the model is a new index that estimates the potential of the atmosphere for hailstorm development, referred to as potential hail index. Validations with independent data sets confirm the reliability of the model results. For Germany, the logistic hail model applied to reanalysis data over the past decades shows a markedly north-to-south gradient with most of the potential hail days occurring in the south. Applied to an ensemble of seven regional climate model simulations, it is found that the potential for hail events will increase in the future (2021-2050) compared to the past (1971-2000), but only statistically significant in the northwest and south of Germany.}, language = {en} } @inproceedings{BrueckPohleKeuleretal., author = {Br{\"u}ck, Yasemine and Pohle, Ina and Keuler, Klaus and Schaller, Eberhard and Hinz, Christoph}, title = {Do mining lakes in the Lusatian Lignite mining region (Eastern Germany) affect regional precipitation patterns?}, series = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Due to the flooding of former open-pit mines, Europe's largest artificial lake district is created in Eastern Germany. Between 1990 and 2006 more than 80 km² of new lakes have already been formed. These large-scale land cover changes may impact regional meteorological characteristics, therefore it is of interest, whether effects of the mining lakes can already be observed. We especially focus on whether the evaporation from the mining pit lakes leads to a higher precipitation on their lee side. To detect changes in the precipitation patterns, we analysed daily precipitation data (1980-2014) of 25 stations in an area of 10 000 km² widely around the lake district. Under the assumption that the influences of the lakes should be detectable either directly as trends in the observed data or as a deviation from a general measure for precipitation we combined statistical tests and principal component analysis (PCA). We applied pre-whitening Mann-Kendall tests to detect precipitation trends and Mann-Whitney tests to detect differences between split samples (before and after the flooding of most of the lakes). The PCA was applied based on the correlation matrix of daily precipitation at the different stations. As the daily precipitation can sufficiently be explained by the first five principal components, the recombination of these five principal components was used as a general measure of precipitation in the region. By regression trees (random forests) a relation between the eigenvectors of the first five principal components and physiogeographic characteristics of the stations (e.g. altitude) was shown. Both the observed data and the deviations between the measurements and the recombination of the first five principal components showed divergent trends with high spatial variability and also interannual variability, but a pattern consistent with the lee side of the lake could not be detected. Therefore, it has been demonstrated that the emerging lakes had no influence on the daily precipitation at the stations considered in this study. This may be explained by the coarse spatial and also temporal resolution of precipitation measurements. Still, the approach presented here can be applied to (i) detect changes in the spatial pattern of climate variables by a combination of statistical tests and PCA and (ii) to analyse the relationships between such changes and physiogeographic characteristics by regression trees.}, language = {en} } @misc{MaciasGarcia‑GorrizDosioetal., author = {Macias, Diego and Garcia‑Gorriz, Elisa and Dosio, Alessandro and Stips, Adolf and Keuler, Klaus}, title = {Obtaining the correct sea surface temperature: Bias correction of regional climate model data for the Mediterranean Sea}, series = {Climate Dynamics}, volume = {51}, journal = {Climate Dynamics}, number = {3}, issn = {0930-7575}, doi = {10.1007/s00382-016-3049-z}, pages = {1095 -- 1117}, abstract = {Here, the COSMO Climate Limited-area Modelling (CCLM) regional climate model (RCM) is used as external forcing for a Mediterranean basin-scale ocean model based on the general estuarine transport model (GETM). CCLM is forced by different global climate models (GCMs) (MPI and EcEarth) and by the ERA-interim (ERAin) reanalysis. Sea surface temperatures (SST) simulated by the different runs of the ocean model are compared with satellite measurements. As a substantial cold bias in simulated SST is found, a simple bias-correction methodology is applied to the RCM atmospheric variables, namely (1) air temperature (which is usually underestimated for the region by RCMs runs), (2) cloud cover (typically overestimated) and (3) wind intensity (as zonal wind intensity is usually overestimated). The performed analysis identifies wind velocity as the most important variable to correct in order to satisfactorily obtain Mediterranean SST. For many of the RCM realizations significant improvement in the simulated SST are only achieved when wind intensity values were bias-corrected towards observed values. Air temperature and cloud cover had a more marginal importance in reducing the SST bias observed in RCM-forced runs of the ocean model. By comparing the ERAin-driven run and the GCMs driven runs, our analyses suggest that the main source of observed bias is related with the GCMs being used as lateral boundary condition for the RCM realizations. However, a relative simple bias-correction methodology is sufficient to reduce a large part of the induced bias in SST and to improve the vertical water stratification characteristics within the Mediterranean basin that will allow to analyze current and future biogeochemical conditions of the studied basin.}, language = {en} } @misc{KeulerRadtkeKotlarskietal., author = {Keuler, Klaus and Radtke, Kai and Kotlarski, Sven and L{\"u}thi, Daniel}, title = {Regional climate change over Europe in COSMO-CLM: Influence of emission scenario and driving global model}, series = {Meteorologische Zeitschrift}, volume = {25}, journal = {Meteorologische Zeitschrift}, number = {2}, issn = {0941-2948}, doi = {10.1127/metz/2016/0662}, pages = {121 -- 136}, abstract = {The variability of climate change over Europe is analyzed in a new ensemble of eight high-resolution scenario simulations with the dynamically nested regional climate model COSMO-CLM. The simulations are a contribution of the CLM-Community to EURO-CORDEX - the European branch of the international CORDEX initiative. The study documents the influence of two emission scenarios (RCP4.5 and RCP8.5) and four driving global climate models (MPI-ESM-LR, HadGEM2-ES, CNRM-CM5, EC-EARTH) on the climate change signal of seasonal near-surface air temperature, seasonal precipitation amount and daily precipitation intensity in eight different regions of Europe. Both temperature and precipitation changes show comparable spatial patterns across the ensemble. The warming magnitude, however, strongly depends on the emission scenario and the driving GCM. The analysis demonstrates that the influence of the driving GCM on the temperature change signal can be of comparable magnitude as the influence of the emission scenario. For seasonal precipitation changes the influence of the driving GCM is even more important. All ensemble members show a consistent increase in the frequency of days with intense precipitation while the total number of precipitation days decreases. A further aspect is the comparison between the climate change signals in the regional and the driving global simulations. A critical intensity class is used to quantify the transition from decreasing to increasing precipitation frequencies. The analysis reveals that the variability of frequency changes is smaller in the regional than in the global model ensemble, which can be interpreted as an improved robustness and a possible added value of the regional projections. It is also shown that the regional simulations tend to reduce the seasonal mean temperature change of the driving global simulation. In some seasons and regions the damping of the warming signal can amount to more than 2K. Overall, the analysis reveals a strong influence of comparable magnitude of the choice of the emission scenario and the driving global model on regional climate change signals, and stresses the necessity of a large regional model ensemble for a reliable and robust assessment of regional climate change.}, language = {en} } @misc{KotlarskiSzaboHerreraetal., author = {Kotlarski, Sven and Szabo, Peter and Herrera, Sixto and R{\"a}ty, Olle and Keuler, Klaus and Soares, Pedro and Cardoso, Rita M. and Bosshard, Thomas and Pag{\´e}, Christian and Boberg, Fredrik and Guti{\´e}rrez, Jos{\´e} and Isotta, Francesco and Jaczewski, Adam and Kreienkamp, Frank and Liniger, Mark and Lussana, Cristian and Pianko-Kluczyńska, Krystyna}, title = {Observational uncertainty and regional climate model evaluation: A pan-European perspective}, series = {International journal of climatology}, volume = {39}, journal = {International journal of climatology}, number = {9}, issn = {1097-0088}, doi = {10.1002/joc.5249}, pages = {3730 -- 3749}, language = {en} } @misc{HuebenerHoffmannKeuleretal., author = {H{\"u}bener, Heike and Hoffmann, Peter and Keuler, Klaus and Pfeifer, Susanne and Ramthun, Hans and Spekat, Arne and Steger, Christian and Warrach-Sagi, Kirsten}, title = {Deriving user-informed climate information from climate model ensemble results}, series = {Advances in Science and Research}, volume = {14}, journal = {Advances in Science and Research}, issn = {1992-0628}, doi = {10.5194/asr-14-261-2017}, pages = {261 -- 269}, language = {en} } @misc{KnocheKeuler, author = {Knoche, Richard and Keuler, Klaus}, title = {Dynamische Regionalisierung}, series = {Promet : meteorologische Fortbildung}, journal = {Promet : meteorologische Fortbildung}, number = {99}, issn = {0340-4552}, pages = {29 -- 40}, language = {de} } @techreport{HuebenerBuelowFookenetal., author = {H{\"u}bener, Heike and B{\"u}low, Katharina and Fooken, Cornelia and Fr{\"u}h, Barbara and Hoffmann, Peter and H{\"o}pp, Simona and Keuler, Klaus and Menz, Christoph and Mohr, Viktoria and Radtke, Kai and Woldt, Michael}, title = {ReKliEs-De Ergebnisbericht}, publisher = {Eigenverlag des Hessischen Landesamtes HLNUG}, address = {Wiesbaden}, pages = {56}, language = {de} } @misc{KjellstroemNikulinStrandbergetal., author = {Kjellstr{\"o}m, Erik and Nikulin, Grigory and Strandberg, Gustav and B{\o}ssing Christensen, Ole and Jacob, Daniela and Keuler, Klaus and Lenderink, Geert and Meijgaard, Erik van and Sch{\"a}r, Christoph and Somot, Samuel}, title = {European climate change at global mean temperature increases of 1.5 and 2°C above pre-industrial conditions as simulated by the EURO-CORDEX regional climate models}, series = {Earth System Dynamics}, journal = {Earth System Dynamics}, number = {9}, issn = {2190-4987}, doi = {10.5194/esd-9-459-2018}, pages = {459 -- 478}, language = {en} } @techreport{HuebenerSpekatBuelowetal., author = {H{\"u}bener, Heike and Spekat, Arne and B{\"u}low, Katharina and Fr{\"u}h, Barbara and Keuler, Klaus and Menz, Christoph and Radtke, Kai and Ramthun, Hans}, title = {ReKliEs-De Nutzerhandbuch}, publisher = {World Data Center for Climate (WDCC) at DKRZ}, address = {Hamburg}, doi = {10.2312/WDCC/ReKliEsDe_Nutzerhandbuch}, pages = {II, 86, XIV}, language = {de} } @misc{VautardKadygrovIlesetal., author = {Vautard, Robert and Kadygrov, Nikolay and Iles, Carley and Keuler, Klaus}, title = {Evaluation of the large EURO-CORDEX regional climate model ensemble}, series = {J. Geophys. Res. Atmos.}, journal = {J. Geophys. Res. Atmos.}, issn = {2169-8996}, doi = {10.1029/2019JD032344}, pages = {47}, abstract = {The use of regional climate model-based projections for providing regional climate information in a research and climate service contexts is currently expanding very fast. This has been possible thanks to a considerable effort in developing comprehensive ensembles of regional climate model (RCM) projections, especially for Europe, in the EURO-CORDEX community (Jacob et al., 2014; Jacob et al., 2020). Currently, EURO-CORDEX has developed a set of 55 historical and scenario projections (RCP8.5) using 8 driving global climate models (GCMs) and 11 RCMs. This article presents the ensemble including its design. We target the analysis to better characterize the quality of the regional climate models by providing an evaluation of these RCM simulations over a number of classical climate variables and extreme and impact-oriented indices for the period 1981-2010. For the main variables, the model simulations generally agree with observations and reanalyses. However, several systematic biases are found as well, with shared responsibilities among RCMs and GCMs: simulations are overall too cold, too wet and too windy compared to available observations or reanalyses. Some simulations show strong systematic biases on temperature, others on precipitation or dynamical variables but none of the models/simulations can be defined as the best or the worst on all criteria. The article aims at supporting a proper use of these simulations within a climate services context.}, 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{VanderkelenZscheischlerGudmundssonetal., author = {Vanderkelen, Inne and Zscheischler, Jakob and Gudmundsson, Lukas and Keuler, Klaus and Rineau, Francois and Neenaerts, Natalie and Vangronsveld, Jaco and Vicca, Sara and Thiery, Wim}, title = {A novel method for assessing climate change impacts in ecotron experiments}, series = {International Journal of Biometeorology}, volume = {64}, journal = {International Journal of Biometeorology}, number = {10}, issn = {0020-7128}, doi = {10.1007/s00484-020-01951-8}, pages = {1709 -- 1727}, abstract = {Ecotron facilities allow accurate control of many environmental variables coupled with extensive monitoring of ecosystem processes. They therefore require multivariate perturbation of climate variables, close to what is observed in the field and projections for the future. Here, we present a new method for creating realistic climate forcing for manipulation experiments and apply it to the UHasselt Ecotron experiment. The new methodology uses data derived from the best available regional climate model projection and consists of generating climate forcing along a gradient representative of increasingly high global mean air temperature anomalies. We first identified the best-performing regional climate model simulation for the ecotron site from the Coordinated Regional Downscaling Experiment in the European domain (EURO-CORDEX) ensemble based on two criteria: (i) highest skill compared to observations from a nearby weather station and (ii) representativeness of the multi-model mean in future projections. The time window is subsequently selected from the model projection for each ecotron unit based on the global mean air temperature of the driving global climate model. The ecotron units are forced with 3-hourly output from the projections of the 5-year period in which the global mean air temperature crosses the predefined values. With the new approach, Ecotron facilities become able to assess ecosystem responses on changing climatic conditions, while accounting for the co-variation between climatic variables and their projection in variability, well representing possible compound events. The presented methodology can also be applied to other manipulation experiments, aiming at investigating ecosystem responses to realistic future climate change.}, 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} }