Convection-permitting climate simulations with COSMO-CLM for Germany: Analysis of present and future daily and sub-daily extreme precipitation

Abstract

Extreme precipitation has the potential to induce flash floods, causing severe damage on infrastructure at the local to regional scale. Simulating the most extreme rainfall intensities is still very challenging and highly uncertain under climate change. A convection-permitting regional climate model is used to estimate return levels dependent on the rainfall duration and return period for Germany. A comparison to radar- and station-based datasets reveals high-resolution model abilities to reproduce observed extreme precipitation statistics ranging from hourly to daily timescales. Among others, the model performance reveals a good agreement for extreme rainfall intensities for durations above 12 hours independent of the return period. An overestimation for hourly extreme precipitation intensities is still apparent. A comparison to several lower-resolution models using convection parameterisations shows the advantage of applying a convection-permitting setup for improving the spatial distribution and reducing the mean relative bias of extreme precipitation estimation over Germany. Finally, changes in extreme precipitation statistics are estimated under climate change for the convection-permitting model and placed in contrast to results obtained by state-of-the-art regional climate models. A 30 % mean increase in intensity is projected for the end of the 21st century assuming a high-end emission scenario for daily precipitation extremes over Germany. The convection-permitting simulation does not show a further increase in intensity for sub-daily heavy rainfall estimates under global warming, as contrasted with regional climate models using parameterised convection.

Keywords

• extreme precipitation
• convection-permitting
• climate change
• return period