Testing the effect of a two-way-coupling of a meteorological and a hydrologic model on the predicted local weather

A land-surface module to couple a meteorological and a hydrologic model was developed to simulate the water cycle in a closed manner. The module allows to consider the hydrologic processes of the river catchment (translation, retention, lateral discharge) in the meteorological model which itself drives the hydrologic model by predicted evapotranspiration and precipitation. Besides this two-way-coupling, the module allows to consider subgrid-scale surface processes and to heterogenize precipitation in the meteorological model. The results of 24-h simulations with and without a two-way-coupling of the models substantiate that even on a short time scale surface runoff and lateral water flows affect soil wetness, soil temperature, cloudiness and the thermal regime of the atmospheric boundary layer within the catchment. As expected, the coupling results in a slight trend towards moister valleys and drier hills.