EC-EARTH successfully tested in a high resolution configuration

A high-resolution configuration of the earth system model EC-EARTH 3 has been developed at the Rossby Centre. First tests of the system revealed the challenging nature of performance analysis and optimisation of coupled models, however, EC-EARTH shows good scalability, compared to standalone runs of ECMWF's atmospheric model IFS.

EC-EARTH 3, which is continuously developed by a consortium of European climate research groups, is a coupled earth system model comprising ECMWF's atmospheric model IFS, the general ocean circulation model Nemo, the LIM sea ice model, and the OASIS coupler.

Additional component models are being integrated as development is proceeding. The development of the most recent version 3 of the system is coordinated at the Rossby Centre and includes up-to-date versions of the component models as well as a newly implemented infrastructure to configure, build, and run the model.

The newly implemented high-resolution configuration of EC EARTH 3 is based on ¼ degree horizontal grids for the atmosphere (T799/N800 grid) and ocean (ORCA025 grid), which is a about a sixteenfold increase in the number of grid points per model level, compared to the currently used configuration.

A first step towards high-resolution climate simulations

The set-up is a first, technical, step towards high-resolution climate simulations and provides practical insights for the scientific discussion on that topic. It is intended to prove and improve the capabilities of EC-EARTH 3 as a scientific tool and to study and optimise the scalability on massively parallel machines.

First tests of the system revealed the challenging nature of performance analysis and optimisation of coupled models, however, EC-EARTH shows good scalability, compared to standalone runs of IFS. Tests with up to just over 1600 cores suggest that scalability and parallel efficiency are highly sensitive to various configuration parameters. Load balancing is crucial for efficient runs on many processing cores, and I/O activity, not surprisingly, becomes increasingly important.

The work on a high-resolution set-up was boosted by the collaboration with CERFACS, Toulouse, in the context of the Dedicated OASIS User Support 2010 and with National Supercomputer Centre (NSC) in Linköping within the IS ENES project. As a consequence of the positive results, EC-EARTH 3 was selected the first model to be used in the IS ENES – PRACE collaborative effort to port earth system models to the next generation high performance computing facilities.