Difference between revisions of "Photolysis mechanism"

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This page describes some of the updates to the FAST-J photolysis mechanism, as is currently implemented in GEOS-Chem.
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Here we link to pages describing the various versions of the FAST-J and FAST-JX photolysis mechanisms used in GEOS-Chem.
  
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== Input files for FAST-J ==
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== Photolysis mechanisms used in standard GEOS-Chem versions ==
  
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The following input files are required for the FAST-J photolysis mechanism:
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The following photolysis mechanisms have been implemented in official releases of GEOS-Chem:
  
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;[http://www.as.harvard.edu/ctm/geos/doc/man/chapter_5.html#5.4.1 ratj.d]: This file is where you specify each of the FAST-J photolysis species.  Each species is mapped to a corresponding entry of the GEOS-Chem chemical mechanism.
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=== FAST-JX v7.0 ===
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;[http://www.as.harvard.edu/ctm/geos/doc/man/chapter_5.html#5.4.2 jv_atms.dat]: This file specifies the reference O3 climatology for FAST-J.  NOTE: GEOS-Chem will overwrite this reference climatology with TOMS/SBUV data for those months and locations where such data exists.
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;[http://www.as.harvard.edu/ctm/geos/doc/man/chapter_5.html#5.4.3 jv_spec.dat]: This file is where the various quantum yields and aerosol cross-sections are specified.
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== O1D reaction updated to JPL 2006 ==
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The [[FAST-JX v7.0 photolysis mechanism]] is the newest version of the FAST-J software.  It was incorporated into [[GEOS-Chem v10-01]] by Sebastian Eastham (MIT) and the [[GEOS-Chem Support Team]], along with the [[UCX chemistry mechanism|UCX stratospheric-tropopsheric chemistry mechanism]].
  
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As of GEOS-Chem v8-01-02, the rate constants in the "FAST-J" [http://www.as.harvard.edu/ctm/geos/doc/man/chapter_5.html#5.4.2 jv_atms.dat file] have been updated by Lin Zhang.
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--[[User:Bmy|Bob Yantosca]] ([[User talk:Bmy|talk]]) 17:06, 16 November 2016 (UTC)
  
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These were the old values:
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=== FAST-J ===
  
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O3_1d  180 9.000E-01 9.000E-01 3.824E-01 8.092E-02 7.650E-02      0.0      0.0
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The [[FAST-J photolysis mechanism]] was used in GEOS-Chem versions prior to [[GEOS-Chem v10-01]].  It has since been replaced by [[FAST-JX v7.0 photolysis mechanism]].
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O3_1d  260 9.000E-01 9.000E-01 4.531E-01 1.438E-01 7.654E-02      0.0      0.0
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  O3_1d  300 9.000E-01 9.000E-01 5.273E-01 2.395E-01 7.659E-02      0.0      0.0
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which are now replaced by the new values from JPL 2006:
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--[[User:Bmy|Bob Yantosca]] ([[User talk:Bmy|talk]]) 17:07, 16 November 2016 (UTC)
  
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O3_1d  180 9.000E-01 9.000E-01 3.824E-01 8.092E-02 7.650E-02      0.0      0.0
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== Photolysis mechanisms used in research versions of GEOS-Chem ==
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O3_1d  260 9.000E-01 9.000E-01 4.531E-01 1.438E-01 7.654E-02      0.0      0.0
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O3_1d  300 9.000E-01 9.000E-01 5.273E-01 2.395E-01 7.659E-02      0.0      0.0
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For more information, please contact Lin Zhang (lzh@io.as.harvard.edu).
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The following photolysis mechanisms have been used in non-standard research versions of GEOS-Chem:
  
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--[[User:Bmy|Bob Y.]] 11:16, 23 May 2008 (EDT)
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=== FAST-JX v6.2 ===
  
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== Cloud overlap options in FAST-J ==
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The [[FAST-JX v6.2 photolysis mechanism]] was implemented into several research versions of GEOS-Chem by Jingqiu Mao (Princeton).  But this version of FAST-J was never incorporated into the standard GEOS-Chem model.
  
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GEOS-Chem now has 3 cloud overlap options in the FAST-J photolysis mechanism:
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--[[User:Bmy|Bob Y.]] 11:58, 20 May 2014 (EDT)
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:1. '''Linear cloud overlap assumption:'''  This is the default in GEOS-Chem versions [[GEOS-Chem_versions_under_development#v8-01-01|v8-01-01]] and prior.  The option is:
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    Grid Box Optical depth = In-cloud optical depth * Cloud fraction. 
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:2. '''Approximate random overlap assumption:'''  This option will be introduced into the standard code in GEOS-Chem v8-01-02 (benchmark run #1).
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    Grid Box Optical Depth = In-Cloud Optical Depth * ( Cloud Fraction )^1.5
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:3. '''Maximum random overlap assumption:'''  This option is much more computationally intensive, and therefore is not used as the default option.  However, if you wish to use this option, then manually edit the <tt>fast_j.f</tt> source code file such that <tt>OVERLAP = 3</tt>. 
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:The Maximum-Random Overlap (MRAN) scheme assumes that clouds in adjacent layers are maximally overlapped to form a cloud block and that blocks of clouds separated by clear layers are randomly overlapped.  A vertical profile of fractional cloudiness is converted into a series of column configurations with corresponding fractions see Liu et al., JGR 2006; hyl,3/3/04).
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:For more details about cloud overlap assumptions and their effect on photolysis frequencies and key oxidants in the troposphere, refer to the following articles:
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:#Liu, H., et al., ''Radiative effect of clouds on tropospheric chemistry in a global three-dimensional  chemical transport model'', <u>J. Geophys. Res.</u>, '''111''', D20303, doi:10.1029/2005JD006403, 2006.
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:#Tie, X., et al., ''Effect of clouds on photolysis and oxidants in the troposphere, <u>J. Geophys. Res.</u>, '''108'''(D20), 4642, doi:10.1029/2003JD003659, 2003.
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:#Feng, Y., et al., ''Effects of cloud overlap in photochemical models'', <u>J. Geophys. Res.</u>, '''109''', D04310, doi:10.1029/2003JD004040, 2004.
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:#Stubenrauch, C.J., et al., ''Implementation of subgrid cloud vertical structure inside a GCM and its effect on the radiation budget'', <u>J. Clim.</u>, '''10''', 273-287, 1997.
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For more information, please contact Hongyu Liu (hyl@nianet.org).
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--[[User:Bmy|Bob Y.]] 12:35, 23 May 2008 (EDT)
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Latest revision as of 19:47, 2 January 2019

Here we link to pages describing the various versions of the FAST-J and FAST-JX photolysis mechanisms used in GEOS-Chem.

Photolysis mechanisms used in standard GEOS-Chem versions

The following photolysis mechanisms have been implemented in official releases of GEOS-Chem:

FAST-JX v7.0

The FAST-JX v7.0 photolysis mechanism is the newest version of the FAST-J software. It was incorporated into GEOS-Chem v10-01 by Sebastian Eastham (MIT) and the GEOS-Chem Support Team, along with the UCX stratospheric-tropopsheric chemistry mechanism.

--Bob Yantosca (talk) 17:06, 16 November 2016 (UTC)

FAST-J

The FAST-J photolysis mechanism was used in GEOS-Chem versions prior to GEOS-Chem v10-01. It has since been replaced by FAST-JX v7.0 photolysis mechanism.

--Bob Yantosca (talk) 17:07, 16 November 2016 (UTC)

Photolysis mechanisms used in research versions of GEOS-Chem

The following photolysis mechanisms have been used in non-standard research versions of GEOS-Chem:

FAST-JX v6.2

The FAST-JX v6.2 photolysis mechanism was implemented into several research versions of GEOS-Chem by Jingqiu Mao (Princeton). But this version of FAST-J was never incorporated into the standard GEOS-Chem model.

--Bob Y. 11:58, 20 May 2014 (EDT)

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