@inproceedings{KeulerBlockSchaller, author = {Keuler, Klaus and Block, Alexander and Schaller, Eberhard}, title = {Assessment of quality and uncertainty in regional climate simulations}, series = {Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop, high-resolution climate modelling, assessment, added value and applications, Lund, Sweden, 29 March-2 April 2004}, booktitle = {Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop, high-resolution climate modelling, assessment, added value and applications, Lund, Sweden, 29 March-2 April 2004}, editor = {B{\"a}rring, Lars and Laprise, Rene}, publisher = {Lund University}, address = {Lund, Sweden}, pages = {68 -- 69}, language = {en} } @inproceedings{RadtkeKeuler, author = {Radtke, Kai S. and Keuler, Klaus}, title = {Climate change in Europe simulated by the regional climate model COSMO-CLM}, series = {2nd International Lund RCM Workshop : 21st Century Challenges in Regional-scale Climate Modelling, Lund University, Sweden, 4-8 May 2008, workshop proceedings}, booktitle = {2nd International Lund RCM Workshop : 21st Century Challenges in Regional-scale Climate Modelling, Lund University, Sweden, 4-8 May 2008, workshop proceedings}, editor = {Rockel, Burkhardt and B{\"a}rring, Lars and Reckermann, Marcus}, publisher = {International BALTEX Secretariat}, address = {GKSS Forschungszentrum Geesthacht}, pages = {56 -- 57}, language = {en} } @inproceedings{KeulerRadtkeSchaller, author = {Keuler, Klaus and Radtke, Kai S. and Schaller, Eberhard}, title = {Effect of internal variability on regional climate change projections}, series = {2nd International Lund RCM Workshop : 21st Century Challenges in Regional-scale Climate Modelling, Lund University, Sweden, 4-8 May 2008, workshop proceedings}, booktitle = {2nd International Lund RCM Workshop : 21st Century Challenges in Regional-scale Climate Modelling, Lund University, Sweden, 4-8 May 2008, workshop proceedings}, editor = {Rockel, Burkhardt and B{\"a}rring, Lars and Reckermann, Marcus}, publisher = {International BALTEX Secretariat}, address = {GKSS Forschungszentrum Geesthacht}, pages = {132 -- 133}, language = {en} } @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} }