A Investigation of the Sensitivity of Simulated Precipitation to Model Resolution and Its Implications for Climate Studies

Abstract

This paper examines the sensitivity of a regional atmospheric model to horizontal resolution and topographic forcing. The model is run for January and July month-long simulations over the European region at gridpoint spacings ranging from 200 to 50 km and with various topography configurations. Different precipitation parameterizations of complexity and structure similar to those used in present-day climate models are tested. When averaged over the whole continent, the precipitation amounts are more sensitive to gridpoint spacing than to topographic forcing. Topography mostly contributes to spatially redistributing precipitation, and its effect is dominant only over subregions characterized by complex topographical features (e.g., the Alps). Other variables, such as cloudiness, surface energy fluxes, and precipitation intensity distributions are also sensitive to resolution. Finally, simulated precipitation amounts vary with the parameterization scheme used at all resolutions. These results have important implications for climate modeling. They suggest that, when running a model on a wide range of horizontal resolutions, such as in a variable gridpoint spacing configuration, in ?time slice? mode, or within a nested modeling system, the effects of physical forcings (e.g., topography) can be strongly modulated by the direct sensitivity of the model physics formulations to resolution.