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ICON (Icosahedral non-hydrostatic) general circulation model

Scientific area

Solving fully compressible non-hydrostatic equations of motion at very high horizontal resolution.

Short description

The ICON dynamical cores solve the fully compressible non-hydrostatic equations of motion for simulations at very high horizontal resolution. The discretisation of the continuity and tracer transport equations is consistent in a sense that mass of air and its constituents are conserved, which is a fundamental requirement for atmospheric chemistry. Furthermore, the vector invariant form of the momentum equation are used, and thus, vorticity dynamics are emphasised. The new dynamical core solves the system of primitive equations in grid point space on the icosahedral grid, which facilitates the quasi-isotropic horizontal resolution on the sphere and the restriction to regional domains. The discretisation method is defined on a special case of Delaunay triangulation on the sphere, i.e., the icosahedral geodesic grid.
A cloud resolving, or large-eddy simulation (LES) version of the ICON core with ultra-high horizontal grid spacing of approximately 100 m is developed within the BMBF initiative "High definition clouds and precipitation for advancing climate prediction", or HD(CP)2 for short.

ICONThe icosahedral grid used by ICON with a finer refinement for Europe.


  • 458,752 cores (1,835,008 compute threads) on BlueGene/Q (JUQUEEN)
  • up to 65536 cores on SuperMUC

Strong scaling of ICON on JUQUEENStrong scaling for the ICON 120 m HD(CP)2 setup.

Programming language and model

  • Fortran/C
  • MPI/OpenMP

Tested on platforms

  • BlueGene/Q

Application developers

Max-Planck Institute for Meteorology

Deutscher Wetterdienst


Thomas Jahns
Abteilung Anwendungssoftware
Deutsches Klimarechenzentrum GmbH
Bundesstraße 45a
20146 Hamburg

Catrin Meyer
Simulation Laboratory Climate Science
Jülich Supercomputing Centre
Forschungszentrum Jülich GmbH
52425 Jülich

(Text and images provided by the developers, taken from the Technical Report FZJ-JSC-IB-2015-01)