OpenIFS programme

The ECMWF OpenIFS programme provides an easy-to-use, exportable version of the IFS in use at ECMWF for operational weather forecasting. The programme aims to develop and promote research, teaching and training on numerical weather prediction (NWP) and NWP-related topics with academic and research institutions.

Use of OpenIFS on topics of interest to the Centre and member states is encouraged. Research topics at ECMWF are described in more detail on the main ECMWF site. Enquiries regarding potential collaborations are welcome.

OpenIFS provides the forecast-only capability of IFS (no data assimilation), stays close to operational version and supports operational configurations. For more details see how OpenIFS compares with IFS.

OpenIFS is supported by a small team at ECMWF for technical & scientific assistance, however, there are limited resources for detailed scientific help.

The OpenIFS model 'package' includes not just the model itself but acceptability tests for compilers/hardware, example case studies, plotting & analysis tools and so on. The model is intended for research and educational use by Universities,  research organisations and individual researchers on their own computer systems. It is not provided for any real-time forecasting. ECMWF does not provide facilities to run OpenIFS on its computer systems.

Documentation, install instructions, frequently asked questions and other help information can all be found on this website. User forums are also available. Support is provided for a range of hardware platforms and compilers.

Please note that OpenIFS is licensed software and not open-source nor in the public domain. Licenses are free of charge and typically granted as site licenses.

About IFS

The ECMWF Integrated Forecasting System (IFS) is ECMWF's modelling and data assimilation framework for global numerical weather prediction (NWP). IFS is a collaborative effort that started between ECMWF and Meteo-France, and today involves many ECMWF member-states and associated consortia of the national meteorological services.

The evolution equations of the IFS are in a terrain following mass-based vertical coordinate (Simmons and Burridge, 1981; Laprise, 1992), solving the hydrostatic, shallow-atmosphere equations (Ritchie et al., 1995) and optionally the non-hydrostatic (deep or shallow) Euler equations (Bubnova et al., 1995; Benard et al., 2010; Wedi et al., 2009; Yessad and Wedi, 2011). The solution procedure is based on the spectral transform method with the first spectral transform model introduced into operations at ECMWF in April 1983. Spectral transforms on the sphere involve discrete spherical harmonics transformations between physical (gridpoint) space and spectral (spherical-harmonics) space. The spectral transform method was introduced to NWP following the work of Eliasen et al. (1970) and Orszag (1970), who pioneered the efficiency obtained by partitioning the computations: one part of the computations is performed in physical space, where products of terms, the semi-Lagrangian (SL) or Eulerian advection, and the physical parameterizations are computed. This technique has been successfully combined with semi-implicit time stepping (Robert et al., 1972), where the resulting Helmholtz problem is solved in spectral space, and the unconditional stability of SL advection (Ritchie, 1988; Temperton et al., 2001), where the only limiting factor on the time step is the magnitude of local truncation errors. With increased computing capacity and the corresponding advances in the numerical techniques applied (Wedi et al., 2013; Wedi, 2014; Wedi et al., 2015), the horizontal resolution has approximately doubled every 8 years, with approximately 9km global grid resolution (and an effective resolution of ~36km) in 2016. In global atmospheric models, subgrid-scale parametrisations describe the effect of unresolved processes on the resolved scale (e.g. surface exchange, convection, gravity wave drag, vertical diffusion), but also describe diabatic effects such as radiation and water phase changes. Both the resolved and the subgrid scale processes in the Earth's atmosphere are the response to mechanical and thermal forcing, associated with the distribution of solar incoming radiation, topography, continents and oceans, sea-ice, waves, vegetation, soil, and other land-use, and are not primarily the result of dynamical instabilities of the atmospheric flow. The IFS has a comprehensive package of sub-grid parametrization schemes representing radiative transfer, convection, clouds, surface exchange, turbulent mixing, sub-grid-scale orographic drag and non-orographic gravity wave drag. The radiation scheme is based on the Rapid Radiation Transfer Model (RRTM) (Mlawer et al., 1997) with cloud radiation interactions using the Monte Carlo Independent Column Approximation (McICA) (Morcrette et al., 2008). Radiation calculations of short- and longwave radiative fluxes are done less frequently than the timestep of the model and on a coarser grid. The moist convection scheme uses the mass-flux approach and represents deep (including congestus), shallow and mid-level (elevated moist layers) convection, see Bechtold et al. (2014) and references therein. Clouds and large-scale precipitation are parametrized with prognostic equations for cloud liquid, cloud ice, rain and snow water contents and a sub-grid fractional cloud cover. The land surface parametrization scheme represents the surface  uxes of energy / water and corresponding sub-surface quantities. It uses a tiled approach (TESSEL) representing different sub-grid surface types for vegetation, bare soil, snow and open water (Balsamo et al., 2009). Turbulent diffusion and exchange with the surface are represented on the basis of Monin-Obukhov similarity in the surface layer and an Eddy-Diffusivity Mass-Flux (EDMF) framework above the surface layer (Kohler et al., 2011). Unresolved orographic effects are represented in the Turbulent Orographic Form Drag (TOFD) scheme for the scales smaller than 5 km (Beljaars et al., 2004) and in the low level blocking and gravity wave scheme for the larger scales (Lott and Miller, 1997). Non-orographic gravity waves are parametrized according to Orr et al. (2010). At the sea surface, the IFS has a two-way coupling to the WAve Model (WAM, Hasselmann et al., 1988) and, in ensemble mode, IFS is coupled to the Nucleus for European Modelling of the Ocean (NEMO, Madec, 2008). The coupling with WAM is performed every time step whereby WAM is forced by IFS 10-metre wind speeds while the IFS is forced by surface roughness over sea. The most important prognostic variable provided by NEMO is the sea-surface temperature (SST) but also information from the ocean surface current is passed to the atmosphere. In the future, time evolving sea-ice information from a dynamic sea-ice model will be passed from NEMO to the atmosphere. NEMO, on the other hand, receives radiation, evaporation-precipitation and wind information (via the WAM model) to drive the ocean circulation. The ocean currently uses a 1 degree resolution and an upgrade to 0.25 degrees is planned in 2016.

The latest scientific documentation of IFS with detailed descriptions of the dynamical core and the physical parametrization package is available from here.

Further information

Further information about OpenIFS, IFS and ECMWF can be found on this website and on the main ECMWF website.

Questions and queries about OpenIFS can be addressed to : openifs-support@ecmwf.int.