OpenIFS for climate modeling

Schematic of the AWI-CM3.1 (grey circle) and FOCI2-OpenIFS (green circle) coupled climate models from AWI and GEOMAR, respectively. Both use the OpenIFS atmospheric model and the OASIS3-MCT coupler. Dark lines show couplings to components currently in use, while light dashed lines show couplings planned for future versions. Note that AGRIF is embedded within the NEMO executable but has its own coupling to OASIS3-MCT.

Current activities and GEOMAR Helmholtz Centre for Ocean Research Kiel and Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) include developing new versions of high-resolution climate models alongside those already existing. Both new versions make use of OpenIFS, a portable version of ECMWF Integrated Forecasting System (IFS), which allows for increased horizontal resolution. The new model configurations have recently been reported in an ECMWF newsletter article (Kjellsson et al. 2020).

Current climate modeling activities at GEOMAR Helmholtz Centre for Ocean Research Kiel and Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) include the development of coupled climate models with eddy rich oceans; FOCI at GEOMAR (Matthes et al. 2020) and AWI-CM at AWI (Sidorenko et al. 2015). Both models reach ocean horizontal resolutions of < 10 km, while the atmospheric horizontal resolution is much coarser: either 100 km (T127) or 200 km (T63). Increasing the horizontal resolution in ECHAM6 comes at a very large computational cost due to poor scalability which is why both institutes have set up experimental configurations of their respective climate models using the OpenIFS atmosphere model – a portable version of the ECMWF’s Integrated Forecasting System (IFS) for use at universities and research institutes. OpenIFS is well suited to run both low and high horizontal resolutions which has allowed both AWI and GEOMAR to run new coupled model experiments with < 10 km ocean resolution and ~ 25 km atmosphere resolution.

Both AWI and GEOMR have integrated these new models into ESM-Tools – a workflow manager for Earth System Models developed within the Helmholtz ESM project (Barbi et al. 2020). ESM-Tools manages the technical aspects of the simulations such as compiling and executing model code, post-processing model output etc. Both models share an OpenIFS version and collaborate in enhancing its ESM capabilities together with ECMWF. The joint model development has strengthened ESM collaborations between AWI and GEOMAR as well as partners at ECMWF which has proven beneficial for all parties.

Test experiments with the two models, dubbed FOCI-OpenIFS and AWI-CM3.1 have been carried out at the ESM partition on the JUWELS supercomputer at Julich Supercomputing Centre and results are currently being analysed. The surface kinetic energy of the ocean shows an eddy-rich  Gulf Stream extension meaning that both models are able to explicitly resolve the baroclinic instabilities and eddy-mean flow interactions in the region (Fig 1). OpenIFS shows a distinct band of precipitation anchored over the Gulf Stream which indicates that the mesoscale activity in the ocean is felt by the atmosphere to a much larger extent than what is possible at coarser resolutions. Ongoing research includes studying the downstream impacts over the North Atlantic and Europe.

FOCI-OpenIFS and AWI-CM3.1 are earmarked for use in a number of studies e.g.:

* The impact of the oceanic mesoscale on atmospheric extremes (ROADMAP project, JPI Oceans)
* Transient changes between glacial cycles (PalMod project, BMBF)

* Heat uptake over the Southern Ocean (SO-CHIC project, Horizon 2020)

For further reading:

Kjellsson, J., Streffing, J., Carver, G., Kohler, M., 2020: From weather forecasting to climate modelling using OpenIFS. ECMWF Newsletter. 164, doi: 10.21957/469hc10jk5

Sidorenko, D., T. Rackow, T. Jung, T. Semmler, D. Barbi, S. Danilov et al., 2015: Towards multi- resolution global climate modelling with ECHAM6-FESOM. Part 1: model formulation and mean climate. Clim. Dyn., 44, doi:10.1007/s00382-014-2290-6.

Matthes, K., A. Biastoch, S. Wahl, J. Harlaß, T. Martin, T. Brücher et al., 2020: The Flexible Ocean and Climate Infrastructure Version 1 (FOCI1): Mean State and Variability, Geosci. Model Dev., 13, 2533– 2568, doi:10.5194/gmd-13-2533-2020.

Barbi, D., N. Wieters, P. Gierz, F. Chegini, S. Khosravi & L. Cristini, 2020: ESM-Tools Version 4.0: A modular infrastructure for stand-alone and coupled Earth System Modelling (ESM). Submitted to Geoscientific Model Development.