Complete this pre-run checklist

Now that you have created a run script for GEOS-Chem Classic, take a moment to make sure that you have completed all required setup steps before running your simulation.

First-time setup

  1. If this is your first-time using GEOS-Chem, make sure that you registered as a new user when you created the run directory.

  2. Make sure that your computational environment meets all of the hardware and software requirements for GEOS-Chem Classic.

Each-time setup

  1. Make sure that you have properly configured your login environment (i.e. load necessary software modules after login, etc.)

  2. Create a GEOS-Chem Classic run directory, and make sure that it is correct for the simulation you wish to perform.

    Attention

    The initial restart file that is included with your run directory does not reflect the actual atmospheric state and should only be used to “spin-up” the model. We recommend a spin-up period of 6 months to 1 year (depending on the type of simulation you are using).

  3. Edit configuration files to specify the runtime behavior of GEOS-Chem Classic..

    Attention

    Be aware that GEOS-FP meteorology is an operational (i.e. evolving) product that is subject to assimilation system updates.

    On the other hand, the MERRA-2 meteorology is a 40+ year reanalysis product performed with a “frozen” version of the NASA GEOS assimilation system. Thus, MERRA-2 is preferable for studies ranging over multiple years or decades.

    Important

    The convection scheme used for GEOS-FP met generation changed from RAS to Grell-Freitas with impact on GEOS-FP meteorology files starting June 1, 2020, specifically enhanced vertical transport. In addition, there is a bug in convective precipitation flux following the switch where all values are zero. While this bug is automatically fixed by computing fluxes online for runs starting on or after June 1 2020, the fix assumes meteorology year corresponds to simulation year. Due to these issues we recommend splitting up GEOS-FP runs in time such that a single simulation does not run across June 1, 2020. Instead. set one run to stop on June 1 2020 and then restart a new run from there. If you wish to use a GEOS-FP meteorology year different from your simulation year please create a GEOS-Chem GitHub issue for assistance.

  4. Configure and build the source code into an executable file.

  5. Create a GEOS-Chem Classic run script to your run directory and edit it for the particulars of your simulation and computer system.

  6. Make sure that your run script contains the proper settings for OpenMP parallelization, either by sourcing an environment file, or by manually adding the settings to the run script.

  7. Be aware of ways in which you can speed up your GEOS-Chem Classic simulations.