Mesoscale meteorological modelling on the VSC: performance evaluation

D. Arnold, I. Schicker, P. Seibert
Institute of Meteorology, University of Natural Resources and Applied Life Sciences, Wien

Nowadays, global climate models (GCM) are providing simulations at best at 100 km resolutions, which may then be used to drive regional climate models (RCM) in order to dynamically downscale, typically down to a grid resolution of 10 km. Nevertheless, this resolution is not sufficient to properly represent the meteorological processes occurring in regions such as the Alps, since valleys and ridges are only marginally resolved. Non-hydrostatic mesoscale meteorological models have shown promising results on the km- and sub-km-scales even for such mountainous regions (e.g., Zängl 2002, 2004, 2007). Although we could not yet afford running these models at such a high resolution for periods as needed in climate studies, this means that the models should be adapted to work in climate mode with resolutions of 1 km or below for such complex areas. This increase of the resolution is quite challenging computationally. Computational demands do not increase linearly with horizontal resolution, but at least quadratic or, depending on the implications for vertical resolution and time-step criteria, even with higher powers. Additionally, RAM and mass storage demands are also increased. This is leading the modelling community towards the intensive use of HPC facilities such as the Vienna Scientific Cluster. Within this context, the HiRmod project aims at a systematic approach to prepare two of the currently most widely used mesoscale meteorological models to create climate-change scenarios at km, or even sub-km, resolution in mountainous terrain making use of the VSC. The models are MM5 version 3.7 (Grell et al., 1994, http://www.mmm.ucar.edu/mm5/) and WRF-ARW version 3.2 (Skamarock et al., 2008, http://www.mmm.ucar.edu/wrf/). Optimum set-ups of the model, including machine-specific set-ups and benchmark tests, are being developed in this project.

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