Validation of the small-scale performance of a climate model

A canonical correlation analysis is used to study the simulation of the relationship between small-scale precipitation patterns near the Alps and large-scale flow patterns by the ECHAM (ECMWF model, HAMburg version) climate model. The analysis is performed on a monthly mean time scale for the winter months of ECHAM1/T21, ECHAM3/T21 (improved model physics) and ECHAM3/T42 (increased resolution) simulations. The obtained patterns are compared with an identical analysis of observational data. The coarse structures of the observed relationships seem to be reasonably well simulated by the ECHAM3/T42 model version despite the simple shape of the model Alps (hereafter the model Alps), while the results for the ECHAM1/T21 and ECHAM3/T21 are not as good. This appears to be not only due to the increased resolution but also to the improved model physics, since some indication of the relationship can be found in the simulation of the ECHAM3/T21, but not in the simulation of the ECHAM1/T21 model version.Paper presented in session OA19/ST15, Simulation of climates using comprehensive global models at the XIX General Assembly of the EGS, Grenoble, 25–29 April 1994