For Beginners

Welcome to the CLM-community!

This page contains specific information for beginners which (hopefully) helps you to have a good start with the COSMO-CLM, ICON-CLM and in the CLM-Community.

You received the user name and password to get access to the community internal content with the Welcome E-Mail.

1. Communication in the CLM-Community

The official language of the CLM-Community is English. The main source of information for the community members in the CLM-Community portal ( Please, make use of the portal and help to keep the content up-to-date. An additional source of information, especially for the COSMO model, is the COSMO home .

Part of the communication in the CLM-Community is done through mailing lists. The list clm_user[at] contains all members of the community. In addition, special mailing lists exist for each working and project group and for the different bodies of the community. You can join or leave working or project groups via your profile in the management tool. Only subscribers of a mailing list can send E-Mails to the list.

After the publication of results obtained with COSMO-CLM, the references and a copy of the publication (peer-reviewed articles as well as theses, reports, etc.) should be sent to the coordination office. The references and, if possible, the publications themselves will be made available on the CLM-Community Portal in the section Outcome. 


2. Structure of the CLM-Community

Working groups

The common tasks and interests around the usage and further development of the model systems are coordinated and conducted in different working groups (WG). Additionally, a changing number of project groups (PG) exist for specific tasks which are limited in time. All community members are encouraged to join one or several of these groups (can be done in your profile).  Each WG and PG has its own mailing list and only the group members receive the mails of the respective list.

The tasks of the working and project group leaders include:

  • coordination of the tasks and activities of the WG/PG

  • organization of the WG/PG meetings at ICCARUS and the CLM Assembly

  • representation of the WG/PG in the coordination groups

  • maintenance or the WG/PG website

Research Overview / Topic Browser

An overview of all research subjects conducted in the community can be found in the science section "Topics" 🔑. According to the community regulations, all members should provide information about their current work with the community models. As a new member, please check if the entry on your topic is correct and complete. In addition, please, use regularly (about once a year) the opportunity to update the research topic description. You can do this directly in the community portal. 


As a member of the community, we ask you to stick to a few rules in order to achieve the common goal of improving the model systems and to facilitate the exchange of information between the community members. In particular, please

  • attend the CLM-Community Assembly and other CLM-Community meetings and workshops if possible. Have a look at the section for information about upcoming meetings.

  • use only the recommended model versions and configurations for production runs and publications.

  • save all necessary information to reproduce your simulations and results: the external data produced by webPEP including the settings for EXTPAR, the scripts, and configuration files used to run the INT2LM and COSMO-CLM, the source code, and the executables of INT2LM and COSMO-CLM, in case you used own model modifications, the COSMO-CLM input if it is not part of an official database, and the COSMO-CLM output.

The rules of collaboration within the community are explained in the documents made available in the section Terms & Conditions . Please, read the CLM-Community Agreement carefully. It is the main document describing the collaboration within the community.

More information about the bodies and members of the community can be found in the section Community .


3. First steps with COSMO-CLM

Starter package

To facilitate the use of the model systems, especially for beginners, a starter package has been created which contains everything that is necessary to run a simulation with COSMO-CLM or ICON-CLM (model source code (COSMO-CLM only), run-scripts, data, short documentation). It is available via the wiki (COSMO-CLM → Starter package and ICON-CLM → Starter package ).

Training / Tutorial

It is recommended to attend the Numerical Model Training Course , which takes place once a year in February/March in Langen near Frankfurt/M., Germany. The last COSMO-CLM training took place in 2019. From 2020 on the training course only covers the ICON modelling framework. A tutorial (COSMO-CLM , ICON-CLM ) is part of the documents which are used during the course. This tutorial might also be helpful as starting point for those who are not able to attend the Training Course.

Source code availability

The recommended version of COSMO-CLM and further CLM subversions are made available via the wiki 🔑 . Other model versions are not recommended for production runs.

The ICON source code (personal license) is made available by the Max Planck Institute for Meteorology (see How_to_obtain_the_model_code).

The code can be accessed after acceptance of the license agreement. The starter package for ICON-CLM (SPICE) and all other scripts and tools for pre-, and postprocessing of the data are made available for members of the CLM-Community via SUPTECH-wiki 🔑 .

Initial and boundary conditions

COSMO-CLM needs initial and boundary data from a global model (climate simulation or reanalysis) and external parameters on the simulation grid as input. Three steps are necessary to prepare the data:

  1. Conversion of the driving model data to INT2LM input-conform NetCDF format (for some models, converter programs are already available 🔑 ). For some input data, this step has already been performed and the INT2LM-ready data are provided at the DKRZ systems. A list of available data can be found via the SUPTECH-wiki .

  2. Processing of the external parameters for interpolation of the physical properties of the region and the vegetation to the model grid. The program which is used for this step is called “” (External Parameter for Numerical Weather Prediction and Climate Application). The interactive web frontend WebPEP@DKRZ (Web interface for Preprocessing External data Parameters) 🔑 is available for the generation of the external parameter files with EXTPAR. The preview at WebPEP@DKRZ is not yet properly working. For checking the domain, please, use the old WebPEP 🔑 which is not producing data files any more.

  3. Finally, the interpolation program INT2LM calculates the initial and boundary conditions using the EXTPAR results and interpolates the coarse grid model fields to the COSMO-CLM grid.

Run and Compile environment

If you don’t have your own run time environment available at your institution, you can use subchain. Subchain is part of the starter package and is available for COSMO-CLM and ICON-CLM .

Model configuration

The model parameters defining the model grid, physics, dynamics, and numerics used in the simulation are defined in Fortran namelists. For an explanation of the parameters included in the namelists and the standard settings, please use the Namelist-Tool-Portal  and have a look at the COSMO User’s Guide .


The scientific documentation of the COSMO model is available on the COSMO web page ( )
Additional information can be found on the CLM-Communtiy portal in the section Documentation.

4. First steps with ICON-CLM

All steps are descibed in the SPICE documentation .

5. User support

The user support is organized by the CLM-Community working group SUPTECH . There are several sources from which community members can get support. 

The wiki 🔑 contains a lot of technical and all source code information.

In case of problems, please post your questions in the CLM-Community forum . Please include all information necessary to understand the problem (you can also upload files such as the error report, the YUSPECIF file showing your model configuration, or plots of the output).

To report bugs one has to fill out the “New issue” form for the respective Project (i.e. part of the model system) on the wiki page. Before you fill out the form, please make sure, that the issue you encountered is really a bug and has not been caused by another problem. Before a bug is reported the issue should be discussed in the forum.

Several other utilities are available which can be used by all community members, such as the Namelist Tool, the starter package, or some postprocessing software. An overview is available here .

In case of questions related to the community membership, please contact the coordination office .


🔑 = CLM-Community login required