TY - GEN A1 - Casanueva, Anna A1 - Keuler, Klaus A1 - Kotlarski, Sven A1 - Herrera, Sixto A1 - Fernández, Jésus A1 - Gutiérrez, J. M. A1 - Boberg, Fredrik A1 - Colette, Augustin A1 - Bøssing Christensen, Ole A1 - Goergen, Klaus A1 - Jacob, Daniela A1 - Nikulin, Grigory A1 - Teichmann, Claas A1 - Vautard, Robert T1 - Daily precipitation statistics in a EURO-CORDEX RCM ensemble: Added value of raw and bias-corrected high-resolution simulations T2 - Climate Dynamics N2 - 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. KW - dded value; Bias correction; EURO-CORDEX; Precipitation indices; Regional climate models Y1 - 2016 U6 - https://doi.org/10.1007/s00382-015-2865-x SN - 1432-0894 VL - 47 IS - 3/4 SP - 719 EP - 737 ER - TY - GEN A1 - Prein, Andreas A1 - Gobiet, Andreas A1 - Truhetz, Heimo A1 - Keuler, Klaus A1 - Goergen, Klaus A1 - Teichmann, Claas A1 - Fox Maule, C. A1 - Meijgaard, Erik van T1 - Precipitation in the EURO-CORDEX 0.11° and 0.44° simulations: high resolution, high benefits? T2 - Climate Dynamics N2 - 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. KW - Regional climate modeling KW - EURO-CORDEX KW - Extremes Y1 - 2016 U6 - https://doi.org/10.1007/s00382-015-2589-y SN - 0930-7575 SN - 1432-0894 VL - 46 IS - 1 SP - 383 EP - 412 ER - TY - CHAP A1 - Brück, Yasemine A1 - Pohle, Ina A1 - Keuler, Klaus A1 - Schaller, Eberhard A1 - Hinz, Christoph T1 - Do mining lakes in the Lusatian Lignite mining region (Eastern Germany) affect regional precipitation patterns? T2 - European Geosciences Union, General Assembly 2016, Vienna, Austria N2 - 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. Y1 - 2016 UR - http://meetingorganizer.copernicus.org/EGU2016/EGU2016-7663.pdf N1 - EGU2016-7663 PB - European Geophysical Society CY - Katlenburg-Lindau ER - TY - GEN A1 - Keuler, Klaus A1 - Radtke, Kai A1 - Kotlarski, Sven A1 - Lüthi, Daniel T1 - Regional climate change over Europe in COSMO-CLM: Influence of emission scenario and driving global model T2 - Meteorologische Zeitschrift N2 - 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. KW - Regional climate change KW - COSMO-CLM KW - EURO-CORDEX KW - dynamical downscaling Y1 - 2016 UR - http://www.schweizerbart.de/content/papers/download/85532 U6 - https://doi.org/10.1127/metz/2016/0662 SN - 0941-2948 SN - 1610-1227 VL - 25 IS - 2 SP - 121 EP - 136 ER -