Aerosol-only simulation

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On this page we describe the aerosol-only (a.k.a. offline aerosol) simulation.

Description

The aerosol simulation is an offline simulation for aerosol tracers only. It uses archived monthly mean OH, NO3, O3 and total nitrate concentrations archived from a previous full-chemistry simulation (more on that below), as well as production and loss rates for H2O2. This simulation does not provide "tagged" capabilities, but reduces the suite of tracers from full chemistry.

Assumptions

  1. OH concentrations are taken from a previously run full chemistry simulation. The default is from a much earlier version of the model, when OH thought to be more realistic. The standard code uses OH from version 5-07-08, with GEOS3 meteorology.
  2. O3, NO3 and total nitrate (HNO3+NIT) concentrations, as well as production rates and photolysis rates for H2O2 are taken from a previously run full chemistry simulation. The current default fields were produced from a GEOS-4, v7-02-03 simulation. These files are generally located in the sulfate_sim_200508/offline/ directory in your GEOS-Chem data directories.

Practicalities

As with all other Offline chemistry simulations, the GEOS-Chem user community shall be responsible for the scientific content and validation of the aerosol-only simulation.

Tracer list

In a complete aerosol-only simulation there are 31 tracers (see input.geos below).

The offline aerosol is simulation type 10. For a full set of aerosol tracers (based on the 59-tracer full-chemistry SOA simulation), the input.geos should look like this:

Type of simulation      : 10
Number of Tracers       : 31
Tracer Entries -------> : TR#  Name   g/mole Tracer Members; () = emitted 
Tracer #1               : 1    DMS    62.00
Tracer #2               : 2    SO2    64.00
Tracer #3               : 3    SO4    96.00
Tracer #4               : 4    MSA    96.00
Tracer #5               : 5    NH3    17.00
Tracer #6               : 6    NH4    18.00
Tracer #7               : 7    NIT    62.00
Tracer #8               : 8    H2O2   34.00
Tracer #9               : 9    BCPI   12.00
Tracer #10              : 10   OCPI   12.00
Tracer #11              : 11   BCPO   12.00
Tracer #12              : 12   OCPO   12.00
Tracer #13              : 13   ALPH   136.23
Tracer #14              : 14   LIMO   136.23
Tracer #15              : 15   ALCO   142.00
Tracer #16              : 16   SOG1   150.00
Tracer #17              : 17   SOG2   160.00
Tracer #18              : 18   SOG3   220.00
Tracer #19              : 19   SOG4   130.00
Tracer #20              : 20   SOG5   150.00
Tracer #21              : 21   SOA1   150.00
Tracer #22              : 22   SOA2   160.00
Tracer #23              : 23   SOA3   220.00
Tracer #24              : 24   SOA4   130.00
Tracer #25              : 25   SOA5   150.00
Tracer #26              : 26   DST1   29.00
Tracer #27              : 27   DST2   29.00
Tracer #28              : 28   DST3   29.00
Tracer #29              : 29   DST4   29.00
Tracer #30              : 30   SALA   36.00
Tracer #31              : 31   SALC   36.00

This list can be reduced by turning off any aerosol species (eg. SOA, dust, SS, etc). You may also run without the secondary organic aerosols (ALPH, LIMO, ALCO, SOG{1,2,3,4,5}, SOA{1,2,3,4,5}) if you wish (but we recommend that you use them).

Run directories

We recommend that you create the run directory for your aerosol-only (a.k.a offline aerosol simulation) from one of the GEOS-Chem full-chemistry run directories.

First, use Git to download one of the full-chemistry run directories for the simulation with secondary organic aerosols.

Next, edit the TRACER MENU section of the input.geos file so that only the aerosol tracers are listed.

Next, create a new restart file that contains only the aerosol tracers. The easiest way to do this is with GAMAP. Start GAMAP and Then all you’d have to do is change the number of tracers in “input.geos”. You could also create a new restart file with GAMAP. Start GAMAP with:

 gamap, file=’restart.4x5.geos5.2004010100', 'IJ-AVG-$'

Then pick the tracers you want to save, and type

  S25-56     # this is DMS .. SALC in the 59-tracer SOA fullchem file

and when prompted for an output file name, type

  restart.4x5.geos5.2004010100.aer_only

and press "OK". Make sure to add this restart file name to the SIMULATION MENU section of your input.geos file.

You may also need to create an SOA restart file which contains the concentrations of various short-lived secondary organic aerosol quantities.

Please also see the following references:

  1. GEOS-Chem User's Guide: Chapter 5: GEOS-Chem run directories
  2. GEOS-Chem User's Guide: Chapter 6.1.6: Checklist for offline aerosol chemistry simulation

--Bob Y. 17:12, 3 March 2011 (EST)

Recent aerosol-only updates

1.

More Information

For more information, see the GEOS-Chem manual pages about offline aerosols:

http://acmg.seas.harvard.edu/geos/doc/man/chapter_6.html#6.1.6
http://acmg.seas.harvard.edu/geos/doc/man/appendix_1.html#A1.8