Frequently asked questions about GEOS-Chem

On this page we shall answer some commonly asked questions about GEOS-Chem.

Basic information about GEOS-Chem

For new users

• I am a GEOS-Chem new user. What is expected of me?
• Where can I find user manuals for GEOS-Chem and related software?
• Can I use GEOS-Chem on cloud-computing platforms?
• What types of simulations can I run with GEOS-Chem?
• What is the horizontal resolution and vertical resolution of GEOS-Chem?
• Which meteorological data fields can be used by GEOS-Chem?
• To whom may I direct GEOS-Chem-related questions?
• What does the GEOS-Chem Steering Committee do?
• What do the GEOS-Chem Working Groups do?
• What does the GEOS-Chem Support Team do?
• I see that there are several GEOS-Chem email lists. How can I subscribe?

Science questions

Where can I find information about ...

• types of GEOS-Chem simulations that I can run?
• bromine chemistry?
• The chemical solver used in GEOS-Chem?
• the Linoz stratospheric ozone chemistry scheme?
• the advection scheme in GEOS-Chem?
• the boundary layer mixing schemes in GEOS-Chem?
• the cloud convection schemes in GEOS-Chem?
• The Dry deposition and Wet deposition schemes in GEOS-Chem?
• GEOS-Chem nested grid simulations?

Technical issues

• How do I download the GEOS-Chem source code and run directories?
• What should I do when I encounter an error while running GEOS-Chem?
• Do you have any information about GEOS-Chem performance and GEOS-Chem scalability?
• Where can I learn more about the GEOS-Chem Makefiles?
• Is there a comprehensive list of GEOS-Chem bug reports?
• Do you have any information on how I can debug GEOS-Chem or HEMCO errors?

Parallelization issues

• How can I tell if a variable has to be declared with !$OMP PRIVATE or !$OMP SHARED?
• How many CPUs may I use for my GEOS-Chem simulation?
• Why is GEOS-Chem not using all the CPUs that I requested?

High-Performance GEOS-Chem (GCHP)

Please see the GCHP user manual at gchp.readthedocs.iofor more information.

Where can I get restart files for GEOS-Chem?

For instructions on how to obtain a set of sample restart files that you can use to spin up your own simulations, please visit this link.

Running GEOS-Chem

Please see our Running GEOS-Chem wiki page.

How long does GEOS-Chem take to run?

It depends on your particular computing environment. We have posted several timing results from GEOS-Chem 7-day time test simulations.

GEOS-Chem seems to be running too slowly. What can I do?

There are several ways to speed up a slow GEOS-Chem simulation.

If you are archiving many diagnostic quantities are a high temporal resolution (e.g. every hour), then this will increase the run time of your simulation. You can try saving out less diagnostic quantities, or archiving at a lower temporal resolution (e.g. every day).

GEOS-Chem errors

Please also see our Guide to GEOS-Chem error messages and Debug GEOS-Chem and HEMCO errors pages.

GEOS-Chem died with an error. What can I do?

Please see Understanding the different categories of errors section of our Guide to GEOS-Chem error messages.