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Running the prep script will take a few minutes and will result in new data that will be written to $AC_IC_DIR, by default this location is $SCRATCH/43r3/experiments/{exp}/chem_ic.

This folder serves as a staging area for the initial and boundary conditions data and if the target files in $AC_IC_DIR already exist then they they will not be overwritten. 

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In order to restart with atmospheric composition tracers from the AC-for-IC grib file select the following settings in config.h:

• Leave Either leave the variable OIFS_INIDATA_DIR empty, delete it or delete/ comment it out.
• Set the variable AC_IC_ONCE to point to the generated AC-for-IC grib file from the previous experiment. This file is typically found in this location in the previous experiment:
  ${RUNDIR}/output/${RUN_NUMBER}/ICMUA${EXP}.ac_rst
  
• Set the variable MET_IC_DIR to the relevant path for the new experiment's initial conditions or modify the "variables to retrieve METEO initial conditions from an archived experiment" section as appropriate.

Running

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the forecast experiment

Now the actual forecast experiment can be submitted to the batch scheduler using the platform-specific job wrapper script. Examples for this are found in $OIFS_HOME/AC-experiments/platform. An example template for the ECMWF HPCF Atos Sequana XH2000 is the file ecmwf-hpc2020.job.tmpl. 

The actual forecast experiment will be carried out inside the run directory. By default this is set to $SCRATCH/43r3/experiments/${exp}/runs/. which is defined in config.h with variable RUNDIR. The default on the ECMWF HPCF is $SCRATCH/43r3/experiments/${exp}/runs/.

Due to the much increased computational requirements for simulating atmospheric composition, forecast experiments are often broken into individual parts (sometimes referred to as "legs"). For each leg a restart of the forecast experiment needs to be carried out. 

Model Output
The oifs-run.sh script for OpenIFS/AC has been designed to be able to cope with restarts or "legs", and the model output from each experiment leg is stored in individual subfolders named by leg number. In the case of a single forecast experiment without restarts the output will be written to $RUNDIR/output/001.

Log files
Log file and experiment-related configuration data (namelist, NODE file, ifs.stat), as well as text files with diagnostic model outuput (e.g. mass and ozone budgets) are copied to $RUNDIR/log/001.

Restart Data
Model data relevant for restarts (not discussed here on this page) will be stored in $RUNDIR/restart/${next_leg_number}.

XIOS output
Files relevant to XIOS server output are stored in $RUNDIR/ifs_xml (not discussed here on this page). 

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Multiple forecasts with restarts

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