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 PLUS bromine species	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
isoprene	NOx-Ox-hydrocarbon-aerosol species PLUS 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)