View source for 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 ===

* [[GEOS-Chem welcome letter for new users|I am a GEOS-Chem new user.  What is expected of me?]]
* [[Minimum system requirements for GEOS-Chem|On what types of machines can I run GEOS-Chem?]]
* [http://acmg.seas.harvard.edu/geos/doc/man/appendix_1.html What kind of simulations can I run with GEOS-Chem?]
* What is the [http://acmg.seas.harvard.edu/geos/doc/man/appendix_2.html horizontal resolution] and [http://acmg.seas.harvard.edu/geos/doc/man/appendix_3.html vertical resolution] of GEOS-Chem?
* [http://acmg.seas.harvard.edu/geos/doc/man/appendix_4.html Which meteorological data fields can be used by GEOS-Chem?]
* [[GEOS-Chem programming staff|To whom can I direct GEOS-Chem-related questions?]]
* [http://acmg.seas.harvard.edu/geos/geos_steering_cmte.html What does the GEOS-Chem Steering Committee do?]
* [http://acmg.seas.harvard.edu/geos/geos_working_groups.html What do the GEOS-Chem Working Groups do?]

=== Science questions ===

Where can I find information about ...

* [[Chemistry Issues|the Standard chemistry mechanism in GEOS-Chem?]]
* [[Dicarbonyls simulation|the Dicarbonyls mechanism in GEOS-Chem?]]
* [[New isoprene scheme|the Caltech isoprene mechanism as implemented in GEOS-Chem?]]
* [[Bromine chemistry mechanism|the bromine chemistry mechanism in GEOS-Chem?]]
* [[KPP solvers FAQ|the KPP chemical solver?]]
* [[Linoz stratospheric ozone chemistry|the Linoz stratospheric ozone chemistry scheme?]]
* [[Offline chemistry simulations|offline chemistry simulations?]]
* [[Emissions overview|emissions options in GEOS-Chem?]]
* [[Advection scheme TPCORE|the advection scheme in GEOS-Chem?]]
* [[Boundary layer mixing|the boundary layer mixing schemes in GEOS-Chem?]]
* [[Cloud convection|the cloud convection schemes in GEOS-Chem?]]
* The [[Dry deposition]] and [[Wet deposition]] schemes in GEOS-Chem?

=== Technical questions ===

* [[Using Git with GEOS-Chem#Downloading a new GEOS-Chem version|How do I download the GEOS-Chem source code and run directories?]]
* [[Downloading GEOS-Chem source code and data#Data Directory Access|How do I download the GEOS-Chem data directories?]]
* [[Common GEOS-Chem error messages|What should I do when I encounter an error while running GEOS-Chem]]?
* Do you have any information about [[GEOS-Chem supported platforms and compilers|GEOS-Chem performance]] and [[GEOS-Chem performance|GEOS-Chem Scalability]]?
* [[Bugs and fixes|Is there a comprehensive list of GEOS-Chem bugs and how they were fixed?]]
* [[GEOS-Chem programming resources|I am new to programming.  Do you have any online resources or tutorials?]]
* [http://acmg.seas.harvard.edu/geos/doc/man/appendix_7.html Is there a recommended programming style that I should use?]
* Are there any [[Floating point math issues|numerical issues]] or [[Machine issues & portability|machine-dependent issues]] that I should be aware of?

== Specific questions ==

=== Can I run two GEOS-Chem jobs simultaneously? ===

'''''[mailto:timmyf@prl.res.in Timmy Francis] wrote:'''''

:I would like to know if I can run more than one executables (.geos) by renaming them as .geos1, .geos2 etc. For example using the same restart file, I want to run two simulations, one 'with chemistry' and the other 'without chemistry' after make and rename the executables to geos1 and geos2 and run these in two terminals. Will they interfere with each other and affect the result?

'''''[mailto:yantosca@seas.harvard.edu Bob Yantosca] replied:'''''

:I recommend creating separate run directories for each executable.  You can place the identical restart file and input files into each run directory.  Then in one run directory you can turn on chemistry in input.geos, and then in the other run directory, you turn off chemistry in input.geos.  If you run the GEOS-Chem executables in two separate directories, you will ensure that one executable will not overwrite the files that the other executable creates.

:In theory, you should be able to run two simultaneous GEOS-Chem executables in two separate run directories.  However, I don't know much about your particular machine.  You might find that there is not enough memory to run two simulations at the same time.  That is not a problem with GEOS-Chem, but with your system (and is something that the GEOS-Chem Support Team wouldn't be able to help you with).

:I would recommend talking with your local IT department to find out how much memory etc. is available to you, and if you would be able to run two simulations at the same time.  I think a 4x5 full chemistry simulation takes 2-3 GB of memory, and a 2x2.5 simulation can take up to 8GB of memory.

--[[User:Bmy|Bob Y.]] 16:58, 3 November 2010 (EDT)