Ben Murphy, U.S. Environmental Protection Agency
Before CMAQv5.2, POA was assumed to be nonvolatile and represented by two model species for all sources: POC, which represents organic carbon mass; and PNCOM, which represents non-carbon organic mass. In CMAQv5.2, species were introduced to represent the semivolatile partitioning and gas-phase aging of POA. In this model version, users were able to choose from chemical mechanisms with semivolatile POA or mechanisms with nonvolatile POA, depending on their application. This arrangement led to a lot of overhead in both develpoment and use since the model had to be recompiled in order to toggle between options.
Beginning with CMAQv5.3, both nonvolatile and semivolatile POA approaches are supported in every mechanism. Every Aerosol chemical namelist contains both the semivolatile and nonvolatile species and every chemical mechanism will compute the aging of both sets of species. It is up to the user to direct the emissions from every source stream to either the nonvolaitle or semivolatile species depending on the assumptions they would like to enforce about the volatility distribution of the organic particulate compounds emitted from each stream. This assumption is invoked through the DESID emission control interface. There is documentation available in the emission control interface file template to guide users through the process of setting this volatility. By default, all source streams are assumed to be semivolatile.
This improvement dramatically reduces the maintenance cost of providing an option for nonvolatile POA. It does increase slightly the operational cost since, for example, semivolatile POA species will have to be transported in CMAQ even if the user is not passing any emissions to these species. However, the total runtime for CMAQ is not affected signicantly by this penalty.
CCTM/src/MECHS/cb6mp_ae6_aq/AE_cb6mp_ae6_aq.nml
CCTM/src/MECHS/cb6mp_ae6_aq/EmissCtrl_cb6mp_ae6_aq.nml
CCTM/src/MECHS/cb6mp_ae6_aq/SpecDef_cb6mp_ae6_aq.txt
CCTM/src/MECHS/cb6r3_ae6_aq/AE_cb6r3_ae6_aq.nml
CCTM/src/MECHS/cb6r3_ae6_aq/EmissCtrl_cb6r3_ae6_aq.nml
CCTM/src/MECHS/cb6r3_ae6_aq/RXNS_DATA_MODULE.F90
CCTM/src/MECHS/cb6r3_ae6_aq/RXNS_FUNC_MODULE.F90
CCTM/src/MECHS/cb6r3_ae6_aq/SpecDef_cb6r3_ae6_aq.txt
CCTM/src/MECHS/cb6r3_ae6_aq/mech_cb6r3_ae6_aq.def
CCTM/src/MECHS/cb6r3_ae7_aq/AE_cb6r3_ae7_aq.nml
CCTM/src/MECHS/cb6r3_ae7_aq/EmissCtrl_cb6r3_ae7_aq.nml
CCTM/src/MECHS/cb6r3_ae7_aq/RXNS_DATA_MODULE.F90
CCTM/src/MECHS/cb6r3_ae7_aq/RXNS_FUNC_MODULE.F90
CCTM/src/MECHS/cb6r3_ae7_aq/SpecDef_cb6r3_ae7_aq.txt
CCTM/src/MECHS/cb6r3_ae7_aq/mech_cb6r3_ae7_aq.def
CCTM/src/MECHS/cb6r3_ae7_aqkmt2/AE_cb6r3_ae7_aq.nml
CCTM/src/MECHS/cb6r3_ae7_aqkmt2/GC_cb6r3_ae7_aq.nml
CCTM/src/MECHS/cb6r3m_ae7_kmtbr/AE_cb6r3m_ae7_kmtbr.nml
CCTM/src/MECHS/cb6r3m_ae7_kmtbr/EmissCtrl_cb6r3m_ae7_kmtbr.nml
CCTM/src/MECHS/cb6r3m_ae7_kmtbr/RXNS_DATA_MODULE.F90
CCTM/src/MECHS/cb6r3m_ae7_kmtbr/RXNS_FUNC_MODULE.F90
CCTM/src/MECHS/cb6r3m_ae7_kmtbr/SpecDef_cb6r3m_ae7_kmtbr.txt
CCTM/src/MECHS/cb6r3m_ae7_kmtbr/mech_cb6r3m_ae7_kmtbr.def
CCTM/src/MECHS/mechanism_information/cb6mp_ae6_aq/AE6_species_table.md
CCTM/src/MECHS/mechanism_information/cb6mp_ae6_aq/cb6mp_ae6_aq_species_table.md
CCTM/src/MECHS/mechanism_information/cb6r3_ae6_aq/AE6_species_table.md
CCTM/src/MECHS/mechanism_information/cb6r3_ae6_aq/cb6r3_ae6_aq_species_table.md
CCTM/src/MECHS/mechanism_information/cb6r3_ae6_aq/mech_cb6r3_ae6_aq.md
CCTM/src/MECHS/mechanism_information/cb6r3_ae7_aq/AE7_species_table.md
CCTM/src/MECHS/mechanism_information/cb6r3_ae7_aq/cb6r3_ae7_aq_species_table.md
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