Abstract
In the framework of the EURO-CORDEX initiative an ensemble of European-wide high-resolution regional climate simulations on a $$0.11^{\circ }\,({\sim}12.5\,\hbox {km})$$ 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 $$0.44^{\circ }\,({\sim}50\,\hbox {km})$$ 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 $$0.11^{\circ }$$ 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 $$0.11^{\circ }$$ 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 $$0.11^{\circ }$$ 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 $$0.11^{\circ }$$ models becomes even more obvious.
Highlights
The amount, distribution, and intensity of precipitation has major impacts on ecosystems and society, since heavy precipitation may lead to large damages caused by floods, debris flows, or landslides, while the absence of precipitation may cause droughts and has impact on water- and hydropower supply
The results presented in this study strongly suggest that the EURO-CORDEX 0.11◦ hindcast simulations are found to add value to the representation of extreme and mean precipitation compared to their 0.44◦ counterparts by: 1 3
Capable of improving precipitation when forced by boundary conditions from global climate model (GCM) simulations
Summary
The amount, distribution, and intensity of precipitation has major impacts on ecosystems and society, since heavy precipitation may lead to large damages caused by floods, debris flows, or landslides, while the absence of precipitation may cause droughts and has impact on water- and hydropower supply. There are three factors which affect precipitation (Sawyer 1956): (1) cloud processes and convection, (2) the interaction of the atmospheric flow with the surface, and (3) the large-scale atmospheric circulation. Decreasing the horizontal grid spacing in climate models to 0.11◦ can help to improve factors (2) and (3) by better representing surface characteristics (e.g., orography and coastlines) and by more accurately solving the equations of motion. Several studies investigated the influence of model grid spacing on precipitation. By investigating seasonal mean precipitation in nine regional climate model (RCM) simulations from the ENSEMBLES project with 25 and 50 km grid spacing (Rauscher et al 2010) found that spatial patterns and temporal evolution of summertime precipitation (but not for winter) are improved in most 25 km simulations. An improvement of the higher resolution was especially visible in topographically complex regions, which is in line with findings by Chan et al (2013). Chan et al (2013) further emphasize the importance of highly resolved observational data sets to capture regional-scale climate signals
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