The ICON model system, which obtains its name from the usage of spherical grids derived from the icosahedron (ICO) and the non-hydrostatic (N) dynamics used for the atmosphere, is the primary model system at MPI-M. It includes components for the atmosphere (ICON-A), the ocean (ICON-O), the land (ICON-L), and infrastructure. ICON is developed in partnership with the German Meteorological Service (DWD), the German Climate Computing Centre (DKRZ) and the Karlsruhe Institute for Technology (KIT).

The model development strategy at MPI-M is focused on developing the next generation of global storm-resolving (km-scale) Earth system models. At the same time, we aim to better exploit the capabilities of traditional Earth system models to study climate variability and the effect of slow processes on the climate system. These different aims are pursued in two development threads: ICON-Sapphire, which focuses on the development and application of next generation Earth System Models, and ICON-Ruby which emphasizes the application and efficient utilization of our existing models. The Sapphire thread is closely coordinated with technical efforts to adapt ICON to the requirements of the most powerful computer systems for scientific computing and the new workflows these entail.

Ruby and Sapphire


The large wavelength and low frequency of the red color of the ruby gem relates to the large-scale resolving grids and low time step frequency used in ICON-Ruby simulations. Here a traditional set of parameterizations is employed and the development aims at making very large ensembles (ca. 100 members) on time scales of centuries or single simulations over up to 100000 years possible.


The small wavelength and high frequency of the blue color of the sapphire gem relates to the small-scale resolving grids and high time step frequency used in ICON-Sapphire simulations. Only a minimal set of parameterizations is used here. This development aims at experiments on sub-centennial time-scales, and small (ca 10 member) ensembles at slightly coarser (5 km) resolution, with full interaction between atmosphere, ocean and land.

ICON Configurations

ICON-Ruby (ICON-ESM) is based on the ICON component models ICON-A for the atmosphere, ICON-L for the land and ICON-O for the ocean. The model configuration is used mostly in the context of Ruby experiments.

ICON-Sapphire (ICON-LEM) is the ICON configuration for large eddy simulations. The model configuration is used mostly in the context of Sapphire experiments.


The former workhorse model MPI-ESM couples the atmosphere, ocean and land surface through the exchange of energy, momentum, water and carbon dioxide and is based on the model components of ECHAM6 for atmosphere and MPIOM for ocean as well as JSBACH for terrestrial biosphere and HAMOCC for the ocean´s biogeochemistry.

Scientific computing

The scientific computing development paves the way for km-scale Earth system simulations on exa-scale computers.  This includes the adaptation of the ICON model for massive parallelization and new architectures, including GPUs, and the development of workflows, which can cope with the very large data volumes of km-scale Earth system simulations, from their initial production and storage to the evaluation and visualization by scientists.

Code availability

The ICON development partners make the ICON code available to individuals and institutions for the purpose of research.