Contents:

This page contains a quickstart guide for building and using OpenIFS 48r1 at model version 48R1.0.

We describe how to build the model and carry out a few basic tests, how to run an example forecast experiment, for which initial experiment data is made available, and how to visualise the model output by creating plots.

Worked Example:

We explain the model installation and the process of running of a forecast experiment for the ECMWF HPC facility (hpc2020 Atos).

All data files and configuration scripts that are required for the worked example experiment can be found on the ECMWF file system here: /perm/openifs/oifs_data/48r1/example
The model will be installed into $HOME/openifs/openifs_48R1.0/
The example forecast experiment will be set up in directory $PERM/i4xc/

It is important to note that the installation process on hpc2020 will not directly translate to alternative systems

Extract the OpenIFS package

Create your local installation of OpenIFS 48R1.0 by cloning or branching from the git repository with the OpenIFS package.

git clone ssh://git@git.ecmwf.int/~daha/openifs-main-git.git

You will need approximately 4 GB of disk space for the model sources, the bundle packages, and the built model binaries.
Please note that currently access to this repository is restricted to a limited number of users only.

Set up the platform configuration file

The OpenIFS model requires a small number of Linux environment variables to be set for both installation and runs. These are referred to as global environment variables.

The most important environment variable is OIFS_HOME, which is required by all scripts used by the model.

OIFS_HOME describes the location of the OpenIFS model installation and is general the path where the git repository was extracted. For example, if you clone the repository into your $HOME directory then you should set:

export OIFS_HOME=$HOME/openifs/openifs_48R1.0/

The other model environment variables are

OIFS_CYCLE - describes the model cycle (e.g. 48r1) for which this configuration file can be used.
OIFS_DATA_DIR - describes the location of climatological input files that are required to run OpenIFS. These have been installed on the ECMWF hpc2020 in a central and accessible location under /perm/openifs/oifs_data and the information is organised by model cycle.

The required global environment variables, described above, are defined in the Platform configuration file, which needs to be modified for your local OpenIFS installation.

This file can be located anywhere on your file system, however the recommended default location is $OIFS_HOME/bin.
We provide a template for this configuration file in $OIFS_HOME/bin/oifs-config.edit_me.sh.
You should edit this file and update the path set in variable OIFS_HOME with your installation's path.

Once edited the platform configuration file is loaded using the following command:

source /path/to/file/location/oifs-config.edit_me.sh

We recommend to include this command in your Linux shell startup configuration (e.g. in .bashrc).

The above command should also be include in any batch job scripts that are intended to run OpenIFS (described in Section 3)

Previous versions of the OpenIFS model also used a platform configuration file. Since OpenIFS 48r1 the number of variables set inside this file has been reduced to a bare minimum. At present, only the variables OIFS_HOME , OIFS_CYCLE , and OIFS_DATA_DIR need to be set in this file.

Build OpenIFS

In the next step the model binary executable (and other helper programs) will be built.

OpenIFS build system

In contrast to earlier model versions, the building of OpenIFS 48r1 is no longer based on the FCM configuration manager, but uses from now on the ecbuild ECMWF build system that is also used for the ECMWF IFS model, and which uses CMake at its core.

OpenIFS 48r1 is further distributed with a software bundle which automatically installs many required software packages during the build process, such as for instance ecbuild, ecCodes, metkit, etc. Hence, a separate installation of these libraries is no longer required as they have now become part of the OpenIFS distribution.

Starting the build process

The $OIFS_HOME/bin/openifs-test.sh script can be used to build the model and run initial tests.

The script requires key environment variables, such as $OIFS_HOME, to be assigned. Make sure you have sourced the platform configuration script first.
The usage of the script is shown with the command: openifs-test.sh -h
The option -e defines the compiler environment (intel or gnu). The default is intel.

Run the build process and the tests using the following command:

cd $OIFS_HOME
./bin/openifs-test.sh -cbt

It is normal to see warnings during the build process.

The script builds the model binaries for the selected compiler and will run the ifs-test t21 and t42 tests.

Set up a forecast experiment

An example forecast experiment has been prepared for OpenIFS 48r1. The experiment ID is i4xc.

Extract the example forecast experiment i4xc.tgz into a folder in a location suitable for model experiments. This folder will be your experiment directory.

Example:
On the ECMWF hpc2020 our model installation $OIFS_HOME will be in $HOME/openifs and for the experiment we extract the i4xc package to $PERM. The experiment directory shall therefore be $PERM/i4xc/2016092500.

cp /perm/openifs/oifs_data/48r1/example/i4xc.tgz $PERM
cd $PERM
tar -xvzf i4xc.tgz

The experiment directory would ideally be in a different location from the earlier model installation path $OIFS_HOME. In general, you will need more disk space for experiments, depending on the model grid resolution, the duration of the forecast experiment and the output fequency of model results.

Ensure the namelist files for the atmospheric model (fort.4) and for the wave model (wam_namelist) are found in the experiment directory. If they are not already there then you can find them in a subfolder (called ecmwf) inside the experiment directory.

cd $PERM/i4xc/2016092500
cp ./ecmwf/fort.4 .
cp ./ecmwf/wam_namelist .

You will need to copy two further scripts from the OpenIFS package into your experiment directory:

oifs-run: this is a generic run script which executes the binary model program file.
exp-config.h: this is the experiment configuration file that determines settings for your experiment. It will be read by oifs-run.

Copy both files from $OIFS_HOME/bin into your experiment directory.

cd $PERM/i4xc/2016092500
cp $OIFS_HOME/bin/oifs-run .
cp $OIFS_HOME/bin/exp-config.h .

Determine experiment parameters

Namelist:

You should edit the atmospheric model namelist file fort.4. It contains Fortran namelists which control model settings and switches.
An important switch to edit is in namelist NAMRIP the variable CSTOP. Set this to the desired length of the forecast experiment.
Experiment i4xc can be run for up to 144 hours (6 days) by setting CSTOP='h144'.

Experiment configuration file:

You should edit the exp-config.h file which determines settings for this experiment.
The oifs-run script will read the settings from this file.
Alternatively, the settings can be passed to the oifs-run script via command line parameters, which takes precedence over the exp-config.h settings.

If no exp-config.h file is found in the experiment directory, and if also no command line parameters are provided when calling oifs-run, then oifs-run will revert to its own default values which are not appropriate. In any case you should either edit the config.h file appropriately or provide the correct command line parameters.

The exp-config.h file contains the following settings:

OIFS_EXPID="i4xc"       # your experiment ID
OIFS_NPROC=8            # the number of MPI tasks
OIFS_NTHREAD=4          # the number of OpenMP threads
OIFS_GRIDTYPE="l"       # the grid type, either 'l' for linear reduced grid, or 'o' for the cubic octahedral grid
OIFS_RES="255"          # the spectral grid resolution
OIFS_NAMELIST='fort.4'  # the name of the atmospheric namelist file (the default is fort.4, so this line could be omitted)
OIFS_EXE="${OIFS_HOME}/build/bin/ifsMASTER.DP"  # the name and location of the model binary executable
OIFS_PPROC=true         # enable postprocessing of model output after the model run
OUTPUT_ROOT=$(pwd)      # folder where pproc output is created (only used if OIFS_PPROC=true). In this case an output folder is created in the experiment directory. 
LFORCE=false            # overwrite existing symbolic links in the experiment directory
LAUNCH=""               # the platform specific run command for the MPI environment (e.g. "mpirun", "srun", etc).

Running the experiment

After all the necessary edits to the namelists (fort.4) and to the experiment configuration file (exp-config.h) have been completed the model run can be started.

Depending on the available hardware experiments can either be run interactively or as a batch job.

Running a batch job

This method is the preferred way to run OpenIFS, as it is more efficient and it allows more flexibility in using the available hardware resources.

A job wrapper script that is suitable for the locally available batch scheduler needs to be used to call the oifs-run script.

We include the example job wrapper script run.ecmwf-hpc2020.job which is suitable for the ECMWF hpc2020 Atos HPC. It uses the SLURM batch job scheduler.

This script needs to be located inside your experiment directory, and it should be edited as required:

Set the appropriate path for your OpenIFS platform configuration script

The LAUNCH command here is only "srun" without any further options, as the parallel environment settings are provided through the script headers.

# run as batch job:
cd $PERM/i4xc/2016092500
sbatch ./run.ecmwf-hpc2020.job

The job wrapper script will read the exp-config.h file and adopt the selected values. The exceptions are LAUNCH, which is set to "srun" for batch jobs, and OIFS_NPROC & OIFS_NTHREAD for which values from the batch job headers are used.

Running interactively

On the ECMWF hpc2020, running the model script interactively should be fine for lower grid resolutions up to T255L91.

In order to run the experiment interactively, execute the oifs-run script from the command line in your terminal.

If no command line parameters are provided with the oifs-run command, then the values from the exp-config.h will be used.

In the exp-config.h the LAUNCH variable should remain empty (and no --runcmd parameter should be provided in the command line). The oifs-run script will in this case use its default launch parameters: srun -c${OIFS_NPROC} --mem=64GB --time=60 which will work fine for OIFS_NPROC=4 or 8 with experiment i4xc.

# run interactively:
cd $PERM/i4xc/2016092500
./oifs-run

Postprocessing

If in the exp-config.h file the OIFS_PPROC variable has been set to true (or if the --pproc command line parameter was used) then the model output in the experiment directory is further processed after completing the model run.

In this case the script will generate a folder called output_YYYMMDD_HHMMSS , with YYYYMMDD being the current date and HHMMSS the current time.
This avoids accidental modification or overwriting of any previous results when the model experiment is repeated.
The variable OUTPUT_ROOT in exp-config.h determines where this ouput folder will be created. The default location is inside the experiment directory, but when assigning another path to OUTPUT_ROOT this could be created elsewhere.

The postprocessing groups all model output fields and diagnostics into individual GRIB files with ascending forecast time step. Also, a copy of the atmospheric model namelist file fort.4, as well as the ifs.stat and NODE.01_001 log files are moved into the output folder.

This postprocessing is required if the Metview Python script is to be used later to visualise the model output.

Plotting of model output

Here we describe in a brief summary how a small number of plots from the model results can be generated. This permits a first-order sanity check whether the model results look sensible.

For this we use the Metview graphics package developed at ECMWF.

This requires the use of Jupyter Notebooks using a conda environment with Metview and Metview-Python libraries.

On the ECMWF hpc2020 a Jupyterlab session can be started using the command ecinteractive -j

Copy the Metview processing code to your $PERM location:

cp /perm/openifs/oifs_data/48r1/example/mv.tgz $PERM
cd $PERM
tar -xvzf mv.tgz
cd mv

Now we process the OpenIFS model output into a dateset format that can be easily interpreted by Metview using a simplified plotting procedure.

Edit the file oifs_to_mv.sh and change the path variable:

in_dir: this needs to point to the folder where the postprocessed OpenIFS model experiment (from the previous section) is found. Absolute file paths are required for this to succeed.

Afterwards, execute the script by running the command: ./oifs_to_mv.sh. This data conversion may take a couple of minutes to complete.

As a result regular gridded and compressed grib files are generated which can be visualised with by running the enclosed Jupyter Notebook single.ipynb

Carry out the following steps:

On the ECMWF Virtual Desktop Interface (VDI) open a terminal, log into the hpc2020 with command: ssh hpc-login
In the terminal start the Jupyter server on an interactive node, using the command: ecinteractive -k
After the interactive node has started you will be given a weblink to connect to the Jupyterlab session ("To manually re-attach go to <weblink>").
Open a web browser (e.g. Chrome) inside the VDI and paste the weblink into the address field; this will connect to the Jupyter server.
Find $PERM/mv/ipynb/single.ipynb in the browser, open the Notebook and run all cells of the Notebook.

Requirements

Further details on software requirements for OpenIFS (this is not required for ECMWF hpc2020)