The COPS campaign (Convective and Orographically-induced Precipitation Study) which took place in Southwest Germany and East France in summer 2007 provides the opportunity to compare simulated budget components with observations from GPS, precipitation and energy balance measurements for the whole COPS period. The balance components are determined for control volumes comprising the region of interest with dimensions of about 1000 to 10000 km² in the horizontal and 10 km in the vertical. The dependence of the atmospheric water budget on air mass characteristics and the inflow direction is discussed. To explore the impact of topography control volumes are set up in the Rhine Valley as well as in the Black Forest and Swabian Jura.
The volume related comparisons indicate good agreements between simulations and observations encouraging the use of COSMO simulations for water budget analysis. Comparing the data in consideration of all balance components helps to identify deficiencies of the model. Accordingly the overestimation of the atmospheric water vapour changes in COSMO is closely linked to the simulated precipitation amount.
During the summer season the main inflow is directed from the southwest. In such situations, we observe a preponderance of evapotranspiration and precipitation. In the case of a northwesterly inflow moisture divergence nearly balances evapotranspiration. Due to the relatively dry air, the contribution of precipitation is only minor. In the Rhine Valley and the region of the Black Forest and Swabian Jura the partitioning of evapotranspiration and precipitation is similar for the inflow from Southwest and Northwest; the contributions due to moisture convergence respectively divergence differ. We notice that the results are quite sensitive to the persistence of weather situations and the number of days for each inflow characteristic. Concluding the results for the COPS period are put into a climatic context.