Exploring Climate of the Euro-Mediterranean Using a Variable-Resolution Configuration of the Global Community Earth System Model (VR-CESM)

A Variable-Resolution, global configuration of the Community Earth System Model (VR-CESM) in which the atmosphere and land are the only active components is employed to investigate the climate of the Euro-Mediterranean region. Two variable-resolution grids with regionally refined resolutions of 0.25 degrees and 0.125 degrees over the study domain, respectively, are used. The fidelity of these VR-CESM simulations is evaluated considering the near-surface air temperature and precipitation fields for the 2000-2014 period in comparison to available observation-based data sets and those of a coarse resolution (quasi-uniform 1 degrees) control simulation. Our analysis shows that, as a global model, VR-CESM can be employed as an alternative to regional climate models to advance our understanding of the Euro-Mediterranean climate. The improvements obtained are mainly related to a better representation of the complex topography of the region with higher resolution. Increasing the regional resolution to 0.25 degrees generally yields considerable improvements over the control simulation; however, some persistent biases remain. Doubling the highest resolution to 0.125 degrees leads to only modest improvements, primarily in the representation of small-scale processes including representation of extreme events that are of substantial relevance for the present and future of the regional climate.