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?
• On what types of machines can I run GEOS-Chem?
• 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 can 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?

--Bob Yantosca (talk) 17:45, 2 January 2019 (UTC)

Science questions

Where can I find information about ...

• the available chemical mechanisms in GEOS-Chem?
• the bromine chemistry mechanism in GEOS-Chem?
• the KPP chemical solver?
• the Linoz stratospheric ozone chemistry scheme?
• the stratospheric chemistry mechanism?
• Other chemistry simulations such as CO2, CH4, Hg, etc.?
• emissions options in GEOS-Chem?
• 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?

--Bob Yantosca (talk) 17:45, 2 January 2019 (UTC)

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 bugs and how they were fixed?
• I am new to programming. Do you have any online resources or tutorials?
• Are there any numerical issues that I should be aware of?
• Do you have any tools that would help me debug GEOS-Chem more efficiently?

--Bob Yantosca (talk) 17:45, 2 January 2019 (UTC)

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?

--Bob Yantosca (talk) 17:45, 2 January 2019 (UTC)

High-Performance GEOS-Chem (GCHP)

Please see the GCHP main wiki page for information about GCHP.

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 see the Restart Files section of our GEOS-Chem basics wiki page.

--Bob Yantosca (talk) 16:24, 6 January 2017 (UTC)

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?

You should be aware of several compile-time options that will slow down GEOS-Chem. Use these options only for debugging, but not in your production runs.

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 Debugging GEOS-Chem 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.

--Bob Yantosca (talk) 14:40, 17 June 2019 (UTC)