Relevance of sub-grid-scale land-use effects for mesoscale models

Abstract

The dependence of the performance of mesoscale-α and mesoscale-β models on model resolutionand parameterisation of sub-grid-scale land-use effects is investigated for a meteorological situationthat is strongly influenced by local effects. Two mesoscale models of different horizontal resolutionand model physics are applied to the same meteorological situation, and the results are comparedwith observations. Sensitivity studies are performed to estimate the effect of resolution (4 km or 5 kmversus 18 km), parameterisation of sub-grid-scale land-use effects and initial state on the results ofboth models. Results show that the accuracy improves with resolution when simple parameterisationsof sub-grid-scale land-use effects are applied. The inclusion of sub-grid-scale land-use effects withapplication of a flux aggregation method provides the best solution, which is nearly independent of theresolutions used. The use of parameter averaging to account for sub-grid-scale land-use effects wasworse than just using one (main) land-use per grid cell. Initial conditions were also found to have asignificant impact on the results.