Scale dependency of regional climate modeling of current and future climate extremes in Germany

• Published in: Theoretical and applied climatology Vol. 134; no. 3-4; pp. 829 - 848
• Main Authors: Tölle, Merja H., Schefczyk, Lukas, Gutjahr, Oliver
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.11.2018; Springer; Springer Nature B.V
• Subjects: Analysis; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Climate change; Climate models; Climate science; Climatic conditions; Climatic extremes; Climatology; Computer simulation; Convection; Dependence; Earth and Environmental Science; Earth Sciences; Extreme weather; Future climates; Future precipitation; Global temperature changes; High resolution; Modelling; Original Paper; Orography; Precipitation; Precipitation (Meteorology); Precipitation variability; Regional climate models; Regional climates; Resolution; Ridges; Simulation; Spatial variability; Spatial variations; Summer; Summer precipitation; Surface temperature; Temperature effects; Temperature extremes; Waste Water Technology; Water Management; Water Pollution Control; Germany; Dynamical downscaling; Climate change; Regional climate model; Precipitation extremes; Temperature extremes; Convection-permitting
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-017-2303-6

A warmer climate is projected for mid-Europe, with less precipitation in summer, but with intensified extremes of precipitation and near-surface temperature. However, the extent and magnitude of such changes are associated with creditable uncertainty because of the limitations of model resolution and parameterizations. Here, we present the results of convection-permitting regional climate model simulations for Germany integrated with the COSMO-CLM using a horizontal grid spacing of 1.3 km, and additional 4.5- and 7-km simulations with convection parameterized. Of particular interest is how the temperature and precipitation fields and their extremes depend on the horizontal resolution for current and future climate conditions. The spatial variability of precipitation increases with resolution because of more realistic orography and physical parameterizations, but values are overestimated in summer and over mountain ridges in all simulations compared to observations. The spatial variability of temperature is improved at a resolution of 1.3 km, but the results are cold-biased, especially in summer. The increase in resolution from 7/4.5 km to 1.3 km is accompanied by less future warming in summer by 1 ∘ C. Modeled future precipitation extremes will be more severe, and temperature extremes will not exclusively increase with higher resolution. Although the differences between the resolutions considered (7/4.5 km and 1.3 km) are small, we find that the differences in the changes in extremes are large. High-resolution simulations require further studies, with effective parameterizations and tunings for different topographic regions. Impact models and assessment studies may benefit from such high-resolution model results, but should account for the impact of model resolution on model processes and climate change.