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Simulation Laboratory Terrestrial Systems

The SimLab TerrSys (SLTS) of the Centre for High-Performance Computing in Terrestrial Systems (Geoverbund ABC/J) at the Juelich Supercomputing Centre focusses since its setup in October 2012 on numerical simulations of variable complexity of terrestrial systems processes across scales and the advancement of the use of supercomputing facilities in terrestrial research.

© HPSC TerrSysCopyright: HPSC TerrSys


  • Global (environmental / climate) change is affecting terrestrial systems at all scales

  • These physical system changes will be accompanied by major state changes of land surfaces and ecosystems and of the services provided by them with multiple (socioeconomic) impacts

  • Many processes are still poorly understood or reproduced by models


  • Supercomputing offers new perspectives for the simulation, understanding and sustainable management of terrestrial systems

  • Demanding numerical models to investigate terrestrial system processes due to:
  1. Complex, nonlinear transport processes of energy, mass and momentum
  2. Interactions and feedback mechanisms between different compartments of the coupled geo-ecosystem (subsurface, land-surface, atmosphere, reservoirs
  3. Multiple spatio-temporal scales, high resolutions, potentially long runtimes
  4. The need for ensemble simulations to estimate uncertainties
  • Strong record of Geoverbund ABC/J scientists in computational geosciences and terrestrial system simulations

  • Availability of computational resources


  • Interface between the (Geoverbund ABC/J) geo-science community and JSC resources

  • Technical support (e.g. porting of user code, provisioning of standard implementations of relevant modelling systems and related datasets, performance optimization, information dissemination)

  • Coordination and help with SimLab TerrSys related issues of supported research projects (e.g. code maintenance, interchangeable software tools, design of data flow-paths and processing chains, pre- and post-processing, visualisation, data synthesis)

  • Support of (Geoverbund ABC/J) researchers in application for compute time

  • Participation in trainings and workshops

  • Own research activities on HPSC in the geosciences (surface atmosphere coupling, regional climate change projections), national and international collaborations


ParFlow (parallel watershed flow model)

Community Land Model (CLM, biogeophysics, hydrologic cycle, biogeochemistry and dynamic vegetation)

TerrSysMP (Terrestrial System Model Platform, fully coupled regional SVA modelling system consisting of COSMO-CLM-ParFlow coupled with OASIS3)

Weather Research and Forecast Model (WRF/ARW, regional climate model)


The SimLab TerrSys is currently primarily involved in supporting groups of the Geoverbund ABC/J and of the TR32 research effort.

Work encompasses the porting, (performance) testing and (standard) setup of the ParFlow.CLM model and the fully coupled TerrSysMP system for different model domains either regionally (North Rhine Westphalia) or locally (small and meso-scale river catchments) at high resolutions at the sub-km grid scale (both model systems) and at a km scale for continent-wide model domains (ParFlow.CLM). In the latter setup, domains may be as large as 10.5 Mio. grid elements and 6 or more depth layers.

The target architecture at the moment is therefore JUQUEEN, where e.g. ParFlow.CLM scales well with a good efficiency up to a full JUQUEEN rack (16384 tasks) and beyond, but the JUROPA supercomputer is used as well e.g. for smaller problem sizes.

The fully coupled system is likewise trageting at highly scalable architectures, especially when also the atmospheric model component is run at convection resolving resolutions of 3 km and less with very short timesteps. The external coupler OASIS3 is used in order to ensure a higher modularity, more easy upgrades or replacements of model system components and also to promote a more rapid development cycle with relatively few code adjustments. However this MPMD design feature and its fairly complex distribution of tasks needs a lot of scalability testing to determine an optimum run configuration.

When the above configurations are run beyond test cases, validation ore process case studies for longer, transient timespans, e.g. in climate change setups, long runtimes become as well an issue as data handling, processing and storage.

Linked to this are research activities of the SimLab that focus on running the WRF atmospheric model in a climate mode setup in the framework of the Euro-CORDEX initiative as part of the World Climate Research Programme.


Geoverbund Aachen - Bonn - Köln / Jülich (ABC/J)

Institute for Bio- and Geosciences / Agrosphere (IBG-3)

Centre for High-Performance Scientific Computing in Terrestrial Systems (HPSC-TerrSys)

Transregional Collaborative Research Centre 32 (TR32, Patterns in Soil-Vegetation-Atmosphere Systems)

Meteorological Institute of the Rheinische Friedrich-Wilhems-Universität Bonn

An initiative of