Intensification of the water cycle: Regional Aspects D. Lüthi, S. Kotlarski, J. Schmidli, P. Pall, E. Fischer, E. Zubler, L. Schlemmer, W. Langhans, O. Bellprat, J. Arnold, J. Rajczak and C. Schär NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects1

Overview Analysis of ENSEMBLES Data Role of aerosols Plans for European scale simulations Activities in convection resolving modeling NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects2

ENSEMBLES RCMs, x1d.5_SON ( ), relative model bias [%] NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects Courtesy J. Arnold

Change in Extreme Precipitation Events for Alpine Region from ENSEMBLES transient RCM Projections Example: Extreme precipitation in Fall (SON) Change of basic statistic & extreme diagnostics in the NE-Alpine subregion in Fall (SON). Spatial distribution of change for 1-day precipitation extremes with a return value of 5 years in Fall (SON). Ensemble-median over 10 RCMs. IMPORTANT RESULTS Spatially diverse change patterns for precipitation in the mid 21st century across Alpine region. Remarkable differences between northern and southern Alps. Increase of extremes in northern Alpine regions in winter and most notably in fall. Decrease of mean precipitation and frequency in summer and spring across entire Alpine region, most pronounced in the South. NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects Courtesy J. Rajczak

Apparent temperature > 105°F/40.6°C Changes are strongest over humid and warm regions (coasts and river basins) Courtesy E. Fischer

Altitude dependence of climate change signal Courtesy S. Kotlarski NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects

The cloud radiative forcing shows negative trends Enhancement of cloud forcing can be partly explained with decreased tropospheric absorption All-sky conditions: Effect of aerosols is reduced in some regions due to cloud effects (e.g. British I.) Strongest all-sky signal: Mid-Europe (roughly 5 Wm -2 increase) Simulation with explicit Aerosol treatment - ERA40 boundary conditions Courtesy E. Zubler

Plans for European Scale simulations Simulations in the framework of IPCC-CORDEX: Scenarios RCP4.5 and RCP8.2 for a CMIP5-GCM for period with a resolution of 12.5 km 2 more CMIP5-GCM runs will be downscaled in the CLM-community Several tests for configuration choice have been performed. PhD work of Omar Bellprat to develop an objective method for model tuning Special process studies, like influence of snow cover etc. NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects8 Courtesy K. Keuler

Perturbed physics and numerics ensembles Evaluation of model parameter uncertainty Comparison to uncertainty from internal variability Evaluation of annual cycle, interannual variability and extreme statistics Testing performance frameworks Identify important model parameters Courtesy O. Bellprat

Kilometer-scale modeling (Hohenegger et al. 2008, 2009 Jürg Schmidli, Wolfgang Langhans, Linda Schlemmer, ETH Zürich)  = 25 km  = 2.2 km Currently -used in operational weather prediction -used for climate process studies, investigations of numerical settings and idealized simulations -under development for climate scenarios Target: -First use for scenarios within next year

Idealized simulations: role of stability Courtesy L. Schlemmer what are the key parameters to characterize moist convection idealized simulation with flat terrain and periodic boundaries horizontal resolution 2.2km NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects

Kilometer scale modeling: planned activities Nested 12km and 2.2km runs with ERA-interim boundary data for the 12km simulation evaluation of simulations vs. observations evaluate added value from high resolution for Alpine area (precip statistics) if necessary, adjust configuration and rerun evaluation run run (10-30yr) time-slice simulations with GCM boundary data for present and future climate contribute to task1 of HP2C project NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects

Thank you for your attention

ENSEMBLES RCMs, mea_SON ( ), relative model bias [%] NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects Courtesy J. Arnold

Health risk and population density Fischer and Schär (2010) Source IIASA Courtesy E. Fischer

altitude dependence of climate change signal Courtesy S. Kotlarski Alpine region difference period vs NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects

IPCC test configurations yearly cycle of temperature and precipitation bias for PRUDENCE region ME NCCR WP2 Meeting D.Lüthi et al.: Intensification of the water cycle - Regional Aspects17