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This section describes the required steps to carry out a forecast experiment with chemistry. The sequence of steps can be summarised as
(1) generate initial conditions or use existing initial data,
(2) set up experiment parameters in config.h and select the appropriate batch job wrapper script for the HPC hardware,
(3) submit the experiment and monitor progress.

Preparing an experiment

AC-experiments directory overview

The experiment controls are in $OIFS_HOME/AC-experiments/

Here are There the following scripts can be found:

• prep-ic-icmcl-compo.sh  - a script to generate initial conditions for chemical fields for the selected run time. Begin and end date need to be given as an argument.
• config.h  - settings for model installation, paths, and experiment configuration.
• oifs-run.sh  - this script controls the workflow for the experiment: reads experiment config, sets up run directories (in $SCRATCH), loads platform configuration, edits namelists, links to initial conditions and executes OIFS_RUNCMD
• runecmwf-ccaatos.job  wrapper script for oifs-run.sh, required settings for the batch scheduler

In $OIFS_HOME/AC-experiments/platform:

• it is necessary to create a machine config file:  oifs-config.damkecmwf-atos.sh  (we can re-use the one used in t21test_xios_t255ac)

The above ecmwf-atos.job Create a wrapper script to submit the batch job ; is based on templates in the platform directory; the following templates exist:

• ecmwf-ccahpc2020.job.tmpl  tmpl    –    run oifs without XIOS   (try this first!)   this is virtually the same as $OIFS_HOME/AC-experiments/run-cca.job
• ecmwf-cca+xios.job.tmpl    –    run oifs with XIOS     this is virtually the same as $OIFS_HOME/AC-experiments/run-cca+xios.job
• ecmwf-cca-workflow.sh    –    workflow for a run with a series of restarts

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• XIOS
• oifs-config.ecmwf-hpc2020.sh  –  template for the machine config file

 Generating initial data overview

Initial conditions for the standard OpenIFS model can be generated using the OpenIFS Data Hub or alternatively they can be requested from the ECMWF OpenIFS support by email openifs-support@ecmwf.int. This provides initial experiment data and surface boundary conditions for the physical/meteorological NWP forecast model. In order to simulate atmospheric composition further initial and boundary conditions are needed. These can be created using the prep-ic-icmcl-compo.sh script. 

You need to set the following environment variables to the appropriate locations:

OIFS_ICMCL_DIR  –  This points to a directory containing initial conditions for the first day of all months of the year 2010. The ICMCL files contain boundary conditions (e.g. SSTs) for the entire month. 
OIFS_INIDATA_DIR_TM5  –  Points to a directory containing TM5 chemistry scheme initial conditions (with or without aerosol) for 2010-01-01 and boundary conditions (emission fluxes and deposition velocities) for 2010-01-01 to 2010-01-02.
OIFS_INIDATA_DIR_CBA  –  As above but for Bascoe/TM5 chemistry

The prep-ic-icmcl-compo.sh script requires external software: the CDO command line operators to manipulate and analyse climate and NWP model data which are available here: https://code.mpimet.mpg.de/projects/cdo/

You need to edit variables inside the file config.h to correspond with the chosen settings for your experiment before running the script to generate the initial data. The settings are described in the following section.

Forecast without restarts – example settings

Using TM5 chemistry without aerosol

We will run a 2 day forecast starting from 2010-01-01 with TM5 chemistry without aerosol.

Use the following settings in config.h

PLATFORM='ecmwf-atos'
RUNDIR=${SCRATCH}/43r3/experiments\${EXPID}\/runs  # where your experiment will run
AC_IC_DIR=${SCRATCH}/43r3/experiments\${EXPID}/chem_ic  # where your chemical initial conditions will be created
run_end_date="2010-01-03"

rst_freq='3 day'  # run for 3 days without restarts (no multi-leg exp)
USE_RESTART=false   # Do not write restart files (no multi-leg exp)
LCHEM=true
CHEM_SCHEME="tm5"
CHEM_VER="ver15"
OIFS_INIDATA_DIR=path_to_directory_T255L91-tm5-none
AC_IC_ONCE=${OIFS_INIDATA_DIR}/ICMUAoiac.ac_rst'
MET_IC_DIR='${OIFS_ICMCL_DIR}/aabg/2010010100'

LAERO=false
LAERCHEM=false
LCHEM_AEROI=false
LINJ_CHEM=false
LINJ_AER=false
LAEROSFC=false

LWAM=true" config.h
LRLXG=false" config.h
LAC4IC=true" config.h

Then run the prep script for initial conditions

./prep-ic-icmcl-compo.sh 2010-01-01 2010-01-03

We begin with a batch job to run OpenIFS/AC without restarts and without XIOS.  For this purpose we modify run-cca.job:

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