An evaluation of the importance of spatial resolution in global climate and hydrological models based on the Rhine and Mississippi basins

Abstract

Abstract.To study the global hydrological cycle and its response to a changing climate, we rely on global climate models (GCMs) and global hydrological models (GHMs). The spatial resolution of these models is restricted by computational resources and therefore limits the processes and level of detail that can be resolved. We assess and compare the benefits of an increased resolution for a GCM and a GHM for two basins with long observational records; the Rhine and Mississippi basins. Increasing shows no significant differences in discharge for both basins, likely because the hydrological processes depend highly on model parameter values that are not 10 readily available at high resolution. Increasing the resolution of the GCM improved the simulations of the monthly averaged discharge for the Rhine, but did not improve the representation of extreme streamflow events. For the Mississippi basin, no substantial differences in precipitation and discharge were found between the two resolutions input GCM and the two resolutions GHM. These findings underline that there is no trivial route from increasing spatial resolution to a more accurately simulated hydrological cycle at basin scale.