The added value of high-resolution EURO-CORDEX simulations to describe daily wind speed over Europe

In the context of the CORDEX project, an ensemble of regional climate simulations of high resolution on a 0.11º grid has been generated for Europe with the objective of improving the representation of regional to local-scale atmospheric phenomena. However, such simulations are computationally expensive and do not always reveal added value.

In this study, a recently proposed metric (the distribution added value, DAV) is used to determine the added value of the available EURO-CORDEX high-resolution simulations at 0.11º for daily mean wind speed compared to their coarser-gridded 0.44º counterparts and their driving global simulations, from hindcast and historical experiments. The analysis is performed using observations data as a reference. Furthermore, the use of a normalized metric allows for a spatial comparison among different regions and time periods.

In general, results show that RCMs add value to their forcing model or reanalysis, but the nature and magnitude of the improvement on the representation of wind speed vary depending on the model, the region or the season. We found that most RCMs at 0.11º outperform models at 0.44º resolution in terms of their quality to represent measured wind speed PDF. However, the benefits of downscaling are not as clear in the upper tail of the wind speed.
At regional scale, higher DAVs are obtained at 0.11º than 0.44º resolution for all subdomains studied, particularly over the Mediterranean, the Iberian Peninsula and the Alps. With altitude, the 0.11º models represent better the locations below 50 m and above 350 m, while the 0.44º models under-perform with increasing altitude. Overall, DAVs are higher at 0.11º than at 0.44º resolution, probably due to a better performance of local-scale feedbacks at high resolution.