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Marke, Thomas (2008): Development and Application of a Model Interface to couple Land Surface Models with Regional Climate Models for Climate Change Risk Assessment in the Upper Danube Watershed. Dissertation, LMU München: Faculty of Geosciences
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Abstract

In the last decades regional climate models (RCMs) have proven their ability to provide valuable information about potential future changes in the earth’s climate system. Research projects like GLOWA-Danube (Global Change of the Water Cycle) are given the possibility to utilize RCM simulations as meteorological drivers for land surface model components. To adequately describe all sorts of water fluxes in the research area of the Upper Danube watershed the different components of the interdisciplinary DANUBIA model require data in high spatial and temporal resolution. While the latter can be satisfactorily provided by most RCMs, the spatial resolution at which atmospheric processes can be resolved is computationally limited to at best 10 x 10 km at present. A clear need has been identified to develop appropriate methods to bridge the gap between RCMs and high resolution land surface models. The application of such downscaling techniques is in particularly necessary in highly complex terrain, where the limited spatial resolution of RCM simulations does not fully capture the natural climatic variability. In the present work a model interface has been developed that provides adequate scaling techniques to overcome the mismatch between the model scales permitting the investigation of climate change impacts at regional to local scales. Besides the downscaling of meteorological simulations, the coupler scales up fluxes calculated at the land surface and provides the aggregated fluxes as inputs for the RCMs. As the latter allows to consider the nonlinearity and complexity of the interactions between the atmosphere and the land surface as well as the mutual dependency of the respective processes at the investigated scale the approach can be expected to contribute to a better understanding of the complex land-atmosphere-system. A comprehensive description of the implemented algorithms is given. Further first results of one-way coupled model runs using the regional climate model REMO to simulate the atmosphere and the hydrological model PROMET to describe all hydrological relevant processes at the land surface are presented. By comparing the results achieved for a potential future climate to those achieved for past climate conditions the climate change impact on the water resources is analyzed. The model interface SCALMET has been developed in the framework of the GLOWA-Danube Project at the Ludwig-Maximilians-University in Munich. The financial funding of GLOWA-Danube by the German Ministry of Education and Research (BMB+F) is gratefully acknowledged.