GEOS-Chem chemistry mechanisms

On this page, we provide an overview of the chemistry mechanisms used in GEOS-Chem.

NOx-Ox-hydrocarbon-aerosol chemistry and variants

The standard NOx-Ox-hydrocarbon-aerosol (aka "full-chemistry") simulation has undergone several updates in recent GEOS-Chem versions. We

Mechanisms in GEOS-Chem v9-01-03 and prior versions

In GEOS-Chem v9-01-03, users could select from one of four pre-defined chemistry mechanisms:

Mechanism	Description	Nickname	Solvers
standard	NOx-Ox-hydrocarbon-aerosol species + bromine species	Full-chemistry or fullchem	SMVGEAR KPP
SOA	NOx-Ox-hydrocarbon-aerosol species + secondary organic aerosol species	SOA	SMVGEAR KPP-
Dicarbonyls	NOx-Ox-hydrocarbon-aerosol species + dicarbonyl species	Dicarbonyls	SMVGEAR only
isoprene	NOx-Ox-hydrocarbon-aerosol species + isoprene oxidation products	Caltech isoprene scheme, Paulot isoprene scheme	SMVGEAR KPP

The bromine tracers and species were added to the standard mechanism just prior to the release of GEOS-Chem v9-01-03.

-Bob Y. 17:00, 30 September 2013 (EDT)

Mechanisms in GEOS-Chem v9-02 and later versions

Several modifications were made to the chemistry mechanisms that shipped with GEOS-Chem v9-01-03.

Mechanism	Description	Nickname	Solvers
standard	NOx-Ox-hydrocarbon-aerosol species PLUS bromine species PLUS Updates to inorganic chemistry reactions (cf. JPL 10-6) PLUS Methyl peroxy nitrate chemistry PLUS Isoprene oxidation species chemistry (aka "Caltech isoprene scheme") PLUS Fix RO2+HO2 rate constant PLUS Increase of NO3 uptake by aerosol PLUS Removal_of_NOx_and_Ox_partitioning PLUS Inhibition of N2O5 uptake by nitrate aerosol PLUS Improved HO2 uptake by aerosol	Full-chemistry or fullchem	SMVGEAR KPP
SOA	NOx-Ox-hydrocarbon-aerosol species PLUS secondary organic aerosol species	SOA	SMVGEAR KPP-
Dicarbonyls	NOx-Ox-hydrocarbon-aerosol species PLUS dicarbonyl species	Dicarbonyls	SMVGEAR only

--Bob Y. 17:17, 30 September 2013 (EDT)