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MechanismDescription# Species

# Reactions

Mechanism NamePre-processor CodeChemistry Specifier
TSMLT1Troposphere, stratosphere, mesosphere, and lower thermosphere231583 (433 kinetic, 150 photolysis)MZ197_TSMLT1_20180423pp_waccm_tsmlt_mam4??
TS1Troposphere and stratosphere221528 (405 kinetic, 123 photolysis)MZ198_TS1-simpleVBS_20180423pp_trop_strat_mam4_vbstrop_strat_mam4_vbs
MAMiddle atmosphere: stratosphere, mesosphere, and lower thermosphere98298 (207 kinetic, 91 photolysis) pp_waccm_ma_mam4??
MADMiddle atmosphere plus D-region ion chemistry135593 (489 kinetic, 104 photolysis) pp_waccm_mad_mam4??
SCSpecified chemistry for WACCM2912 (11 kinetic, 1 photolysis) pp_waccm_sc_mam4??
CAMSimplified chemistry for CAM to to allow tropospheric aerosol formation327 (6 kinetic), 1 photolysis) modal_aero??

IS THE CHEMICAL SPECIFIER THE SAME AS THE PRE-PROCESSOR CODE WITHOUT THE PP AS IS IN CAMCHEM DEFAULT

The input files and fortran routines for these default mechanisms are located in $CCSMROOT/components/cam/src/chemistry/ in the folder specified by the pre-processor code. The chemistry specifier refers to the chemistry (-chem) specified in "CAM_CONFIG_OPTS" in env_build.xml. For example (in bold), <entry id="CAM_CONFIG_OPTS" value="-phys cam6 -chem trop_strat_mam4_vbs -age_of_air_trcs -offline_dyn -nlev 32">. CAM- CAM-Chem and WACCM compsets are defined in section 4.4 and 4.5 of the CAM6 user guide https://ncar.github.io/CAM/doc/build/html/users_guide/atmospheric-configurations.html. All CAM-Chem compsets default to the TS1 chemical mechanism and WACCM compsets default to TSMLT1 chemical mechanism. The TS1 and TSMLT1 chemical mechanisms are described in Emmons et al., 2018 2019 (in preparation).

To review the chemistry used in a specific compset, build your case as described in Run CAM-Chem on Cheyenne. In the $CASEROOT/CaseDocs folder there are 2 files that describe the chemistry chem_mech.in and chem_mech.doc. Both have similar information describing the species and reaction rates. The chem_mech.doc file is in a more human readable format and includes the differential equations defining the production and loss terms of each species. The chem_mech.in file is the version read by the code, and the version you will alter to make changes to the chemical mechanism.

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