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.

    Attention

    The convection scheme used to generate archived GEOS-FP meteorology files changed from RAS to Grell-Freitas starting 01 June 2020 with impact on vertical transport. Discussion and analysis of the impact is available at https://github.com/geoschem/geos-chem/issues/1409.

    To fix this issue, different GEOS-Chem convection schemes are called based on simulation start time. This ensures comparability in GEOS-Chem runs using GEOS-FP fields generated using the RAS convection scheme and fields generated using Grell-Freitas, but only if the simulation does not cross the 01 June 2020 boundary. We therefore recommend splitting up GEOS-FP runs in time such that a single simulation does not span this date. For example, configure one run to end on 01 June 2020 and then use its output restart to start another run on 01 June 2020.. Alternatively consider using MERRA2 which was entirely generated with RAS, or GEOS-IT which was entirely generated with Grell-Freitas. If you wish to use a GEOS-FP meteorology year different from your simulation year please create a GEOS-Chem GitHub issue for assistance to avoid accidentally using zero convective precipitation flux.

  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.