Downscaling of Era40 in Mountainous Terrain

A novel downscaling approach of the Era40 data set has been taken and results for comparison with observations in Norway will be presented. The method applies a nudging technique in a stretched global model, focused in the Norwegian Sea (67N, 5W). The effective resolution is three times the one of the Era40, equivalent to about 30km grid spacing in the area of focus. Longer waves (The comparison to observations incorporate numerous station data points of i) precipitation (#357), ii) temperature (#98) and iii) wind (#10), and the downscaled data set shows large improvements over Era40. The daily precipitation show considerably reduction in bias (from 50% to 11%), and a two-fold reduction at 99.9%tile (-59% to 29%). The daily temperature showed a bias reduction of about a degree in most areas, and relative large RMSE reduction (from 7.5 to 5.0 except winter). The wind comparison showed a slight improvement in bias, and significant improvements in RMSE.