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

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.