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Extpar is an official COSMO Consortium software that generates external parameter fields used as input for the COSMO and ICON models.


In order to get access to the Extpar repository hosted on the C2SM-RCM GitHub organization, please write an e-mail to the administrator of Extpar:


Once you have access, clone the repository the following:

  1. Clone the repository and all submodules from github using the web protocol: (git clone --recursive https://github.com/C2SM-RCM/extpar.git) or the ssh protocol: (git clone --recursive git@github.com:C2SM-RCM/extpar). If you don't already have an ssh key set up for Github, but would like to do so, follow the instructions
  2. Execute "git submodule update"

Compile and run

In order to run Extpar on Piz Daint at CSCS, use the following steps:

  1. Compile the code following the instructions in the README.compile_run. Several executables (.exe and .py) will be generated in the /bin folder. It doesn't matter where you compile, but the executables should be copied to the /scratch file system for running.
  2. The Extpar raw data files are stored in /store/c2sm/extpar_raw_data/linked_data. If you do not already have access to the s83c group at CSCS, then you need to email katherine.osterried@env.ethz.ch to ask permission.
  3. Adapt a run script in the run_scripts folder to your needs. If you need the S_ORO parameter, make sure to adapt the run_script/extpar_eth_12km.globe.sh script. Make sure to change the following variables:
    • sandboxdir (where on scratch do you want to run the code, should be outside the Extpar repository)
    • netcdf_output_filename
    • Adapt the values in the INPUT_COSMO_GRID/INPUT_ICON_GRID file to provide information about your model grid.
    • Source the Python environment for the Python executables with source /project/g110/extpar_envs/venv_jenkins_daint/bin/activate.
  4. Run the adapted run script- for example using: ./extpar_eth_12km.globe.sh

Web-Interfaces for External Parameters

Currently there are two Web-Interfaces to generate the external parameters automatically:
  • WebPEP - online external parameter file generator for COSMO (CLM login required)
  • PAMORE - online ICON-grid and external parameter file generator for ICON (DWD login required)


A detailed documentation about all features and namelist-parameters available for Extpar can be found in the official documentation.

Known issues

SGSL calculation for GLOBE on Piz Daint

When using the SGSL calculations for GLOBE, please use the lpreproc_oro=.true. This derives the S_ORO fields directly from the original GLOBE-tiles. If you try to use the S_ORO-files provided from /store on Daint, you will end up in a Netcdf: HDF-error while opening the S_ORO-files. For more information please read https://github.com/C2SM-RCM/extpar/issues/185 and https://github.com/C2SM-RCM/extpar/issues/185.

Python Virtual Env

To setup a virtual environment for Python on Daint execute the following:
module load cray-python
python -m venv name_of_your_env
source path_to_venv/bin/activate
pip install configparser
pip install netCDF4
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