What is OpenIFS/AC?

OpenIFS/AC is an extended version of the ECMWF OpenIFS model that allows the additional simulation of atmospheric composition (atmospheric chemistry and aerosol processes).

The standard OpenIFS model does not include treatment of chemistry and aerosol processes. Adding this functionality to OpenIFS/AC opens up new scientific applications of the model, e.g. to study the impact of atmospheric composition on numerical weather prediction (NWP) or the interactions between atmospheric composition and the climate system. 

How can I get access to OpenIFS/AC?

Using OpenIFS requires a software licensing agreement with ECMWF. More information on OpenIFS licensing and model software requirements can be found in the OpenIFS 43r3 User Guide and the OpenIFS Home page. 

OpenIFS/AC is provided as an add-on to the standard OpenIFS model. It can be obtained upon request as additional software to the standard model under the same licence agreement as OpenIFS itself.

Parties interested in using OpenIFS/AC should therefore as a first step contact ECMWF, by emailing openifs-support@ecmwf.int, outlining their proposed use of the model.

What level of support can I get for OpenIFS/AC?

Any user support for OpenIFS/AC (in addition to the regular support provided for the standard OpenIFS model) requires prior agreement as it will be highly dependent on the user's requirements and circumstances. 

In comparison with NWP forecast experiments the modelling of atmospheric composition requires a number of additional choices and decisions regarding the simulation of chemical and aerosol processes (for instance, choices about the chemical reaction mechanism). Further, a much wider range of input data is needed for the model, and the origin of this data similarly will depend on the requirements for the planned research. This refers not only to providing initial atmospheric conditions for the chemistry but also to boundary conditions such as emissions fluxes etc.

It is not possible for ECMWF and the OpenIFS/AC developers to provide input data and model configurations for a wide range of potential use cases. In its initial release OpenIFS/AC comes in a single configuration with input data for one model grid resolution (Tl255L91). This offers the choice between two chemical mechanisms (one for the troposphere and one for troposphere+stratosphere) and a tropospheric bulk aerosol scheme. Users of OpenIFS/AC are expected to have the skill and the resources to adapt the provided model code and the input data for their own specific research needs. 

Potential model users who wish to find out if OpenIFS/AC is suitable for their research are requested to email openifs-support@ecmwf.int with an expression of interest which should include a brief summary of the proposed research. After this a decision can be made to what extent user support can be provided. 

How to use OpenIFS/AC?

The necessary steps to install, build and run OpenIFS/AC for a simple forecast case are described on a dedicated page linked to below.