Comparison of Convective Parameters in MPI-ESM Regional and Global Decadal Hindcasts to ERA-Interim Reanalysis

Within the German research programme MiKlip, a model system for decadal climate prediction is being developed. Within its sub-project STEPCLIM (Severe Thunderstorm Evaluation and Predictability in Climate Models) we studied the ability of the MPI Earth System Model (MPI-ESM), which forms the core of the prediction system, and the ability of downscaled regional simulations to correctly simulate convective environments over Europe. We compared parameters relevant to the modelling of severe convective events to the ERA-Interim reanalysis over central Europe during the period 1960-2013: temperature in the lower troposphere (925 hPa), humidity in the lower troposphere, temperature in the middle troposphere (500 hPa), lapse rates between the lower and middle troposphere, and the lifted index between the lower and middle troposphere. The regional model covers Europe and has a resolution of 0.44°, whereas the global model has a resolution of 1.875°. The models were initialized yearly, in the period 1960-2003 and run 10 years after their respective initialization. The regional model was always run as a 4 member ensemble and the global model as a 15 member ensemble. Both the global and the regional models have a positive bias for temperature in the lower troposphere and a negative bias for temperature in the middle troposphere, resulting in an overestimation of lapse rates in both models. The lower tropospheric humidity has a positive bias in the global model, but a negative bias in the regional model. Finally, the lifted index shows a slight positive bias in the regional model and a strong positive bias in the global model.