Overview

OpenIFS 43r3v2 is based on the ECMWF operational IFS cycle 43r3 which was the operational model at ECMWF from July 2017 to June 2018. OpenIFS 43r3v2 is an upgraded version of the previous release OpenIFS 43r3v1. See below for details of changes.

Anyone wishing to use OpenIFS must have a OpenIFS license (see the list of Licensed Institutes).

Support

Please report any issues or problems with this release to either the OpenIFS User Forums or openifs-support@ecmwf.int.

Model documentation

OpenIFS 43r3v1 is scientifically identical to IFS 43r3. For a full description of the IFS 43r3 operational model, please see IFS manuals in the ECMWF eLibrary.

Summary of scientific changes

OpenIFS 43r3v2 includes all the changes listed below compared to previous release OpenIFS 43r3v1. For more details of the changes introduced between OpenIFS 43r3v1 and the previous release OpenIFS 40r1, please see the Release Notes for OpenIFS 43r3v1. For all changes related to IFS model cycles, please see: Changes in ECMWF IFS model.

Experiment initial files

Due to the changes in the model, such as the additional of the lake model fields and altered land-sea mask, previous experiments created for OpenIFS 40r1 (the ICM* files) can not be used with OpenIFS 43r3v1/2. Users who want to run OpenIFS 43r3 should contact openifs-support@ecmwf.int and request new experiment initial files.

Note that also namelist files (fort.4) can not be used as-is with OpenIFS 43r3. We recommend users contact openifs-support@ecmwf.int for new experiment initial conditions and namelist files appropriate for OpenIFS 43r3.

User experiments can choose to have initial conditions on the new reduced octahedral grid or the linear grid available with OpenIFS 40r1.

Technical changes

Compilers

Compilation configurations are provided for the GNU, Intel and Cray compilers.

OpenIFS 43r3v2 is tested and known to work with the following using the configurations supplied:

Version 15 of the Intel compiler is not recommended as it has known issues with the OpenIFS code. Version 16.0.0 of the Intel compiler may generate compile errors in sufa.F90. We recommend using a more recent version if possible.

The Known Issues page has more information about potential problems with the OpenIFS code.

ecCodes GRIB library

The grib-api GRIB library is no longer supported. Users must install the ECMWF ecCodes GRIB library to use OpenIFS 43r3. The model will fail if grib-api is used.

netCDF library

OpenIFS now depends on the netCDF library to be available in order to read and write files in both ecRad and the wave model components. Compilation of OpenIFS requires the netCDF library to be available. Please see the OpenIFS User Guide for more details.

XIOS parallel I/O server: netCDF model output

The XIOS parallel input/output library allows OpenIFS to pass all output to a separately running program (XIOS) for more efficient performance. XIOS allows for parallel output in netCDF format directly from OpenIFS instead of GRIB output via a single process.  It is configured using XML input files and does not use the NAMFPC model namelist. In addition, XIOS may be configured to compute additional fields such as monthly averages 'on-the-fly' instead of a separate post-processing step after the model is run. 

For instructions on how to download, build and use XIOS with OpenIFS, please see the How-to use XIOS with OpenIFS guide.  By default, OpenIFS assumes that XIOS is not available. Users must have the XIOS library installed on their system and then configure the compilation to use XIOS. Note that even with XIOS linked into OpenIFS it is still possible to enable GRIB output and turn off output via XIOS. It is not possible however, to have both GRIB & netCDF output from XIOS enabled at the same time.

A t21test_xios directory configured to use with XIOS is provided with OpenIFS with some example files.  The command to run OpenIFS, in bin/oifs_run, supports running OpenIFS with and without XIOS enabled.

Please note, that the XML files to configure XIOS must be developed by the user and are more complex to setup than the usual NAMFPC namelist in OpenIFS.  In addition, as XIOS is not used operationally with IFS we are unable to provide anything other than support for configuring and building OpenIFS with XIOS.  Users are strongly recommended to post any queries relating to XIOS to the OpenIFS Forums for help from other users.

Further reading:

Computational aspects and performance evaluation of the IFS-XIOS integration
(ECMWF Tech. Report).

Command line arguments

OpenIFS 43r3 no longer supports command line options to set the forecast length, timestep etc. These settings must now be configured in the namelist NAMARG in the namelists file fort.4.

The command to run OpenIFS, in the file bin/oifs_run, has been modified See the model code in src/ifs/module/yomarg.F90 for more details of the namelist variables to set forecast length, timestep etc.

Namelists changes

There have been a significant number of changes to the model namelists compared to OpenIFS 40r1. It's recommended that users do not attempt to use OpenIFS 40r1 namelists with OpenIFS 43r3 but contact openifs-support@ecmwf.int for new experiment files and matching namelist.

Acknowledgements

The OpenIFS team would like to acknowledge the research and support of ECMWF scientists involved in this release and the contribution of the OpenIFS users mentioned above.