Particulate matter in GEOS-Chem: Difference between revisions

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On this page we provide information about how to compute particulate matter concentrations from GEOS-Chem output.
On this page we provide information about how to compute particulate matter concentrations from GEOS-Chem output.


== Definition of PM2.5 used in GEOS-Chem ==
== Definitions of PM2.5 and PM10 for GEOS-Chem ==


=== Update in GEOS-Chem 13.1.0 ===
=== PM2.5 definition ===


Below is an updated recommendation for the PM2.5 coefficients on the wiki as approved by the Aerosol WG.
Below is the definition of PM2.5 used in GEOS-Chem and approved by the [[Aerosols Working Group]].  


At 35% RH:
This table lists hygroscopic growth factors for PM2.5 constituent species:
* 1.10 for SO4, NIT, and NH4
* 1.05 for OCPI and SOA


At 50% RH:
{| border=1 cellspacing=0 cellpadding=5
* 1.35 for SO4, NIT, and NH4
|-valign="top" bgcolor="#cccccc"
* 1.07 for OCPI and SOA
!width="120px"|Scale factor
!width="200px"|Multiplies these species
!width="120px"|Value at 35% RH
!width="120px"|Value at 50% RH
 
|-valign="top" align="center"
|SIA_GROWTH
|SO4, NIT, NH4
|1.10
|1.35
 
|-valign="top" align="center"
|ORG_GROWTH
|OCPI, SOA
|1.05
|1.07
 
|-valign="top" align="center"
|SSA_GROWTH
|SALA
|1.86
|1.86
 
|}


The OA changes at both RH, and the SIA change at 50% RH are straightforward changes to yield consistency between with the current Kappa-Kohler hygroscopicity parameterization in GEOS-Chem based on Latimer and Martin (2019).  
The OA changes at both RH, and the SIA change at 50% RH are straightforward changes to yield consistency between with the current Kappa-Kohler hygroscopicity parameterization in GEOS-Chem based on Latimer and Martin (2019).  
Line 23: Line 44:
  GrowthFactor = 1 + [{(radiusAtRH_wet / radiusAtRH_dry)^3 - 1} x (Density_Water / Density_DrySpecies)]
  GrowthFactor = 1 + [{(radiusAtRH_wet / radiusAtRH_dry)^3 - 1} x (Density_Water / Density_DrySpecies)]


The DST2 bin includes aerosols with diameter both smaller and larger than 2.5 um. Lengthy discussion with Duncan Fairlie, Aaron van Donkelaar, Colette Heald, Jeff Pierce and Noelle Selin led to the conclusion that 38% of the DST2 bin should be included in the calculation of PM2.5.
Emissions from the Anthropogenic Fugitive, Combustion and Industrial Dust (AFCID) (cf [https://iopscience.iop.org/article/10.1088/1748-9326/aa65a4 Philip et al (2017)] are automatically added to the DST1 bin in most GEOS-Chem simulations.  AFCID is activated by default but can be disabled by the user if so desired.
 
The DST2 bin includes aerosols with diameter both smaller and larger than 2.5 um. Fangqun Yu has recently determined that [[APM_aerosol_microphysics#Dust_Particle_Size_Distribution|30% of DST2 should be included in PM2.5]].  (The prior value of 38%, which had been established by Duncan Fairlie, Aaron van Donkelaar, Colette Heald, Jeff Pierce and Noelle Selin, was used until [[GEOS-Chem 13.4.0]].)


In summary, PM2.5 at 35% RH should be computed as:
In summary, PM2.5 at 35% RH should be computed as:


  PM25 = (NH4 + NIT  + SO4) * 1.10
  PM25 = ( NH4 + NIT  + SO4 ) * 1.10
       + BCPI  
       + BCPI  
       + BCPO  
       + BCPO  
       + (OCPO + (OCPI * 1.05)) * 2.1
       + ( OCPO + ( OCPI * 1.05 ) ) * (OM/OC ratio)  # OM/OC ratio = 2.1 by default
       + DST1  
       + DST1  
       + DST2 * 0.38  
       + DST2 * 0.30                                # F. Yu suggests 30% of DST2 (Nov 2011); prior value was 38% of DST2
       + SALA * 1.86
       + SALA * 1.86
       + SOA  * 1.05
       + SOA  * 1.05
NOTE: 2.1 = ratio of OM/OC


=== Current definition ===
By default, the OM/OC ratio is set to a constant value of 2.1. For users who seek more information on the seasonal and spatial variation of OM/OC in the lower troposphere, we provide the option to use the [http://fizz.phys.dal.ca/~atmos/martin/?page_id=2157 seasonal gridded dataset] developed by [http://www.sciencedirect.com/science/article/pii/S1352231013009151 Philip et al. (2014)]. This dataset has some uncertainty, but offers more information than a global-mean OM/OC ratio in regions where primary organic aerosols have a large fossil fuel source.


by Randall Martin, Daven Henze, Aaron van Donkelaar, and Jeff Pierce:
''NOTE: Some modifications to this basic definition are necessary, depending on the SOA species that are used in a given GEOS-Chem simulation.  See the [[#PM2.5 and PM10 diagnostics for GEOS-Chem|PM2.5 and PM10 diagnostics for GEOS-Chem]] section below for details.''


The PM2.5 calculation should account for aerosol water of PM2.5 in a way that is consistent with the PM2.5 measurements.  The water content of PM2.5 is operationally defined.  In the United States an RH of 35% is [https://www3.epa.gov/ttnamti1/files/ambient/pm25/spec/drispec.pdf often used] and would be appropriate for the benchmark.  In Europe an RH of 50% is often used. 
=== PM10 definition ===


Below are the factors that account for aerosol water in a consistent manner as calculated by Aaron van Donkelaar and Sajeev Philip.
In GEOS-Chem 13.4.0 and later versions, PM10 at 35% RH is computed according to the following formula:


At 35% RH:
PM10 = PM2.5
*1.33 for SO4, NIT, and NH4
      + ( DST2 * 0.7  )
*1.16 for OCPI and SOA
      + DST3
*1.86 for SALA
      + ( DST4 * 0.9  )
      + ( SALC * 1.86 )  # NOTE: The value of 1.86 is the SSA_GROWTH factor at 35% RH


At 50% RH the values are
The constant scale factors for DST2 (70%) and DST4 (90%) were determined by Fanqun Yu from [[APM aerosol microphysics]] simulations. For more information, [[APM_aerosol_microphysics#Dust_Particle_Size_Distribution|please follow this link.]].
*1.51 for SO4, NIT, and NH4
*1.24 for OCPI and SOA
*2.42 for SALA


These growth factors are calculated using the change in radius between different RH.  Essentially, the change in radius between the dry (i.e. 0% RH) and wet (35% or 50% RH) aerosol is treated as a shell of water for the purposes of calculating the additional mass associated with the wet particle. Under this condition, it can be shown that:
''NOTE: Some modifications to this basic definition are necessary, depending on the SOA species that are used in a given GEOS-Chem simulation.  See the [[#PM2.5 and PM10 diagnostics for GEOS-Chem|PM2.5 and PM10 diagnostics for GEOS-Chem]] section below for details.''


GrowthFactor = 1 + [{(radiusAtRH_wet / radiusAtRH_dry)^3 - 1} x (Density_Water / Density_DrySpecies)]
== PM2.5 and PM10 diagnostics for GEOS-Chem ==


The DST2 bin includes aerosols with diameter both smaller and larger than 2.5 um. Lengthy discussion with Duncan Fairlie, Aaron van Donkelaar, Colette Heald, Jeff Pierce and Noelle Selin led to the conclusion that 38% of the DST2 bin should be included in the calculation of PM2.5.
The PM2.5 and PM10 diagnostics belong to the [[History_collections_for_aerosols#The_AerosolMass_collection|the AerosolMass collection]] in the GEOS-Chem History diagnotics). They are computed according to the code below, which may be found in <tt>GeosCore/aerosol_mod.F90</tt>.


In summary, PM2.5 should be computed as:
        !==============================================================
 
        ! P A R T I C U L A T E  M A T T E R
PM25 = (NH4 + NIT  + SO4) * 1.33
        !
      + BCPI
        ! See this GEOS-Chem wiki page for the most up-to-date
      + BCPO
        ! definitions of PM2.5 and PM10 used in GEOS-Chem:
      + (OCPO + (OCPI * 1.16)) * 2.1
        !
      + DST1
        ! <nowiki>http://wiki.geos.chem.org/Particulate_Matter_in_GEOS-Chem</nowiki>
      + DST2 * 0.38
        !==============================================================
      + SALA * 1.86
      + SOA  * 1.16
  NOTE: 2.1 = ratio of OM/OC
 
In GEOS-Chem 13.0.0 and later versions, SOA is defined as:
 
'''When using the Simple SOA option:'''
 
*SOAS = Simple SOA (150 g/mol)
 
'''When using the Complex SOA option:'''
 
*TSOA0, TSOA1, TSOA2, TSOA3 = Lumped semivolatile aerosol products of monoterpene + sesquiterpene ox.
*ASOAN, ASOA1, ASOA2, ASOA3 = Lumped nonvolatile aerosol products of light aromatics and IVOCs
*ISOAAQ = Isoprene SOA from aqueous formation, includes
**SOAGX = Aerosol-phase glyoxal (58 g/mol)
*SOAIE = Aerosol-phase isoprene epoxide (118 g/mol)
**LVOCOA = Aerosol-phase low-volatility non-IEPOX product of ISOPOOH (RIP) oxidation (154 g/mol)
 
''NOTE: Fisher et al (2016, ACP) recommend to Exclude INDIOL from AOD and aerosol mass calculations, as it results in lost mass.  As noted in Fisher et al. (2016, ACP), this is a source of uncertainty and would benefit from an update when more information about this process becomes available.''
 
=== Option to include spatially and seasonally varying OM/OC ===
 
<span style="color:green">'''''This update was included in [[GEOS-Chem v11-02#v11-02e|v11-02e]] (approved 24 Mar 2018).'''''</span>
 
For users who seek more information on the seasonal and spatial variation of OM/OC in the lower troposphere (which by default is set to a constant value of 2.1), we provide the option to use the [http://fizz.phys.dal.ca/~atmos/martin/?page_id=2157 seasonal gridded dataset] developed by [http://www.sciencedirect.com/science/article/pii/S1352231013009151 Philip et al. (2014)]. This dataset has some uncertainty, but offers more information than a global-mean OM/OC ratio in regions where primary organic aerosols have a large fossil fuel source.
 
== PM2.5 diagnostic as implemented in GEOS-Chem ==
 
=== In GEOS-Chem 13.3.1 and later versions:
   
   
         ! Particulate matter < 2.5um [kg/m3]
         ! Particulate matter < 2.5um [kg/m3]
Line 130: Line 118:
         ! double-counting. (bmy, 5/11/18)
         ! double-counting. (bmy, 5/11/18)
         IF ( Is_SimpleSOA ) THEN
         IF ( Is_SimpleSOA ) THEN
           PM25(I,J,L) = PM25(I,J,L) + SOAS(I,J,L) * ORG_GROWTH
           PM25(I,J,L) = PM25(I,J,L) + ( SOAS(I,J,L) * ORG_GROWTH )
           PM10(I,J,L) = PM10(I,J,L) + SOAS(I,J,L) * ORG_GROWTH
           PM10(I,J,L) = PM10(I,J,L) + ( SOAS(I,J,L) * ORG_GROWTH )
   
   
         ELSE IF ( Is_ComplexSOA ) THEN  
         ELSE IF ( Is_ComplexSOA ) THEN  
Line 154: Line 142:
         ! Apply STP correction factor based on ideal gas law
         ! Apply STP correction factor based on ideal gas law
         PM25(I,J,L) = PM25(I,J,L) * ( 1013.25_fp / PMID(I,J,L) ) * &
         PM25(I,J,L) = PM25(I,J,L) * ( 1013.25_fp / PMID(I,J,L) ) * &
                      ( T(I,J,L)   / 298.0_fp   )
                                    ( T(I,J,L) / 298.0_fp     )
   
   
         PM10(I,J,L) = PM10(I,J,L) * ( 1013.25_fp / PMID(I,J,L) ) * &
         PM10(I,J,L) = PM10(I,J,L) * ( 1013.25_fp / PMID(I,J,L) ) * &
                      ( T(I,J,L)  / 298.0_fp    )
                                    ( T(I,J,L)  / 298.0_fp    )


=== Prior to GEOS-Chem 13.3.1 ===
Also note that there are some calculations that were not included in the [[#Definitions of PM2.5 and PM10 for GEOS-Chem|basic definitions of PM2.5 and PM10 in the preceding sections]].  These are:
 
The PM2.5 diagnostic (which belongs to the [[History_collections_for_aerosols#The_AerosolMass_collection|the AerosolMass collection]] in the GEOS-Chem History diagnotics) is computed according to the code below.
 
        !==============================================================
        ! P A R T I C U L A T E  M A T T E R
        !
        ! Compute PM2.5 concentration [kg/m3]
        !
        ! PM25 = 1.33 (NH4 + NIT  + SO4) + BCPI + BCPO +
        !        2.10 (OCPO + 1.16 OCPI) + 1.16 SOA*  +
        !        DST1 + 0.38 DST2 + 1.86 SALA
        !
        !  * If using simple  SOA, SOA = SOAS;
        !    If using complex SOA, SOA = TSOA + ASOA + ISOAAQ
        !
        ! NOTES:
        ! - We apply growth factors at 35% RH (computed above):
        !    1.33 for SO4, NIT, and NH4
        !    1.16 for OCPI and SOA
        !    1.86 for SALA
        ! - Ratio of OM/OC = 2.1 is applied to OCPI and OCPO above
        ! - Aerosol WG recommends including 38% of DST2 in PM2.5
        ! - Use either simple SOA or complex SOA in PM2.5 calculation.
        !  By default simple SOA will be used.
        !
        ! %%% IMPORTANT %%%
        ! Note that if complex SOA is used then PM2.5 includes all
        ! the SOA formed in both the Marais et al. and Pye et al.
        ! schemes and may include some double-counting of isoprene SOA.
        ! (Aerosol WG)
        !==============================================================
        ! Units: [kg/m3]
        PM25(I,J,L) = NH4(I,J,L)        * SIA_GROWTH + &
                      NIT(I,J,L)        * SIA_GROWTH + &
                      SO4(I,J,L)        * SIA_GROWTH + &
                      BCPI(I,J,L)                    + &
                      BCPO(I,J,L)                    + &
                      OCPO(I,J,L)                    + &
                      OCPI(I,J,L)      * ORG_GROWTH + &
                      SALA(I,J,L)      * SSA_GROWTH + &
                      SOILDUST(I,J,L,1)              + & ! DST1
                      SOILDUST(I,J,L,2)              + & ! DST1
                      SOILDUST(I,J,L,3)              + & ! DST1
                      SOILDUST(I,J,L,4)              + & ! DST1
                      SOILDUST(I,J,L,5) * 0.38          ! 38% of DST2
   
        ! Include either simple SOA (default) or Complex SOA in
        ! PM2.5 calculation.  In simulations where both Simple SOA and
        ! Complex SOA species are carried (i.e. "benchmark"), then
        ! only the Simple SOA will be added to PM2.5, in order to avoid
        ! double-counting. (bmy, 5/11/18)
        IF ( Is_SimpleSOA ) THEN
          PM25(I,J,L) = PM25(I,J,L) + SOAS(I,J,L) * ORG_GROWTH
        ELSEIF ( Is_ComplexSOA ) THEN
          PM25(I,J,L) = PM25(I,J,L)                + &
                        TSOA(I,J,L)  * ORG_GROWTH + &
                        ASOA(I,J,L)  * ORG_GROWTH + &
                        ISOAAQ(I,J,L) * ORG_GROWTH    ! Includes SOAGX
          ! Need to add OPOA to PM2.5 for complexSOA_SVPOA simulations
          ! -- Maggie Marvin (15 Jul 2020)
          IF ( Is_OPOA ) THEN
              PM25(I,J,L) = PM25(I,J,L)            + &
                            OPOA(I,J,L) * ORG_GROWTH
          ENDIF
        ENDIF
        ! Apply STP correction factor based on ideal gas law
        PM25(I,J,L) = PM25(I,J,L) * ( 1013.25_fp / PMID(I,J,L) ) * &
                      ( T(I,J,L)  / 298.0_fp    )


=== Avoid double-counting of ISOAAQ species ===
=== Avoid double-counting of ISOAAQ species ===


[[User:jaf|Jenny Fisher]] rightly pointed out that the PM2.5 diagnostic [[Secondary_organic_aerosols#Only_add_ISOAAQ_species_to_PM2.5_diagnostics_for_simulations_using_the_complex_SOA_option|was erroneously including the ISOAAQ species in the accounting of PM2.5 when the Simple SOA option was used]].  After discussion with the [[Aerosols Working Group]], we modified the PM2.5 diagnostic (in routine <tt>aerosol_mod.F90</tt>) accordingly.  
[[User:jaf|Jenny Fisher]] rightly pointed out that the PM2.5 diagnostic [[Secondary_organic_aerosols#Only_add_ISOAAQ_species_to_PM2.5_diagnostics_for_simulations_using_the_complex_SOA_option|was erroneously including the ISOAAQ species in the accounting of PM2.5 when the Simple SOA option was used]].  After discussion with the [[Aerosols Working Group]], we modified the PM2.5 and PM10 diagnostic computations accordingly:  


To avoid double-counting of SOA, we do the following:
To avoid double-counting of SOA, we do the following:
Line 247: Line 164:
'''''Aaron van Donkelaar wrote:'''''
'''''Aaron van Donkelaar wrote:'''''


<blockquote>As currently implemented [in [[GEOS-Chem v11-01]], the PM2.5 diagnostic outputs PM2.5 at ambient conditions.  While this is not technically an error, most PM2.5 monitors measure at STP conditions which will cause disagreement during comparison with observations and inconsistency during application of any health response curves (generally determined from the STP observations).<br>
<blockquote>As was originally implemented in [[GEOS-Chem v11-01]], the PM2.5 diagnostic outputs were at ambient conditions.  While this is not technically an error, most PM2.5 monitors measure at STP conditions which will cause disagreement during comparison with observations and inconsistency during application of any health response curves (generally determined from the STP observations).<br>
 
As a result, I’d recommend applying an STP correction factor based on ideal gas law after PM2.5 is calculated in aerosol_mod.F:</blockquote>
 
        PM25(I,J,L) = PM25(I,J,L) * (1013.25d0 / AIRPRESS(I,J,L)) * (AIRTEMP(I,J,L) / 298)
 
This has since been added to the PM2.5 diagnostic in GEOS-Chem ([[PM2.5 diagnostics as implemented in GEOS-Chem|see code above]]).
 
== Anthropogenic PM2.5 dust source in GEOS-Chem ==
 
<span style="color:green">'''''This update was included in [[GEOS-Chem 12#12.1.0|GEOS-Chem 12.1.0]], which was released on 26 Nov 2018.'''''</span>
 
Sajeev Philip and coauthors have added a new PM2.5 dust emission inventory into GEOS-Chem, termed as Anthropogenic Fugitive, Combustion and Industrial Dust (AFCID).  For information on this inventory, please see our [[Mineral_dust_aerosols#Anthropogenic_PM2.5_dust_source_in_GEOS-Chem|''Mineral dust aerosols'' wiki page]].
 
--[[User:Bmy|Bob Yantosca]] ([[User talk:Bmy|talk]]) 22:27, 11 January 2019 (UTC)


== PM10 ==
As a result, I’d recommend applying an STP correction factor based on ideal gas law after PM2.5 is calculated:</blockquote>


At present there is no PM10 diagnostic in GEOS-Chem. We welcome GEOS-Chem User Community to assist us with implementing this diagnostic.
        PM2.5 = PM2.5 * ( 1013.25 / P ) * ( T / 298 )
        PM10  = PM10  * ( 1013.25 / P ) * ( T / 298 )


--[[User:Bmy|Bob Yantosca]] ([[User talk:Bmy|talk]]) 15:02, 22 February 2021 (UTC)
--[[User:Bmy|Bob Yantosca]] ([[User talk:Bmy|talk]]) 19:41, 3 November 2021 (UTC)

Latest revision as of 13:32, 4 November 2021

On this page we provide information about how to compute particulate matter concentrations from GEOS-Chem output.

Definitions of PM2.5 and PM10 for GEOS-Chem

PM2.5 definition

Below is the definition of PM2.5 used in GEOS-Chem and approved by the Aerosols Working Group.

This table lists hygroscopic growth factors for PM2.5 constituent species:

Scale factor Multiplies these species Value at 35% RH Value at 50% RH
SIA_GROWTH SO4, NIT, NH4 1.10 1.35
ORG_GROWTH OCPI, SOA 1.05 1.07
SSA_GROWTH SALA 1.86 1.86

The OA changes at both RH, and the SIA change at 50% RH are straightforward changes to yield consistency between with the current Kappa-Kohler hygroscopicity parameterization in GEOS-Chem based on Latimer and Martin (2019).

The SIA recommendation at 35% RH is less certain since it depends on the efflorescence RH of the SIA in the aerosol mixture under the variable conditions of the instruments, collection media, and laboratories involved. Given knowledge gaps about the aerosol phase at low RH, the proposed growth factor of 1.1 assumes that half of the particles are aqueous (growth factor of 1.19 for Kappa-Kohler) and the other half are crystalline (growth factor of unity).

These growth factors are calculated using the change in radius between different RH. Essentially, the change in radius between the dry (i.e. 0% RH) and wet (35% or 50% RH) aerosol is treated as a shell of water for the purposes of calculating the additional mass associated with the wet particle. Under this condition, it can be shown that: 

GrowthFactor = 1 + [{(radiusAtRH_wet / radiusAtRH_dry)^3 - 1} x (Density_Water / Density_DrySpecies)]

Emissions from the Anthropogenic Fugitive, Combustion and Industrial Dust (AFCID) (cf Philip et al (2017) are automatically added to the DST1 bin in most GEOS-Chem simulations. AFCID is activated by default but can be disabled by the user if so desired.

The DST2 bin includes aerosols with diameter both smaller and larger than 2.5 um. Fangqun Yu has recently determined that 30% of DST2 should be included in PM2.5. (The prior value of 38%, which had been established by Duncan Fairlie, Aaron van Donkelaar, Colette Heald, Jeff Pierce and Noelle Selin, was used until GEOS-Chem 13.4.0.)

In summary, PM2.5 at 35% RH should be computed as: 

PM25 = ( NH4 + NIT  + SO4 ) * 1.10
     + BCPI 
     + BCPO 
     + ( OCPO + ( OCPI * 1.05 ) ) * (OM/OC ratio)  # OM/OC ratio = 2.1 by default
     + DST1 
     + DST2 * 0.30                                 # F. Yu suggests 30% of DST2 (Nov 2011); prior value was 38% of DST2
     + SALA * 1.86
     + SOA  * 1.05

By default, the OM/OC ratio is set to a constant value of 2.1. For users who seek more information on the seasonal and spatial variation of OM/OC in the lower troposphere, we provide the option to use the seasonal gridded dataset developed by Philip et al. (2014). This dataset has some uncertainty, but offers more information than a global-mean OM/OC ratio in regions where primary organic aerosols have a large fossil fuel source.

NOTE: Some modifications to this basic definition are necessary, depending on the SOA species that are used in a given GEOS-Chem simulation. See the PM2.5 and PM10 diagnostics for GEOS-Chem section below for details.

PM10 definition

In GEOS-Chem 13.4.0 and later versions, PM10 at 35% RH is computed according to the following formula: 

PM10 = PM2.5 
     + ( DST2 * 0.7  )
     + DST3
     + ( DST4 * 0.9  )
     + ( SALC * 1.86 )   # NOTE: The value of 1.86 is the SSA_GROWTH factor at 35% RH

The constant scale factors for DST2 (70%) and DST4 (90%) were determined by Fanqun Yu from APM aerosol microphysics simulations. For more information, please follow this link..

NOTE: Some modifications to this basic definition are necessary, depending on the SOA species that are used in a given GEOS-Chem simulation. See the PM2.5 and PM10 diagnostics for GEOS-Chem section below for details.

PM2.5 and PM10 diagnostics for GEOS-Chem

The PM2.5 and PM10 diagnostics belong to the the AerosolMass collection in the GEOS-Chem History diagnotics). They are computed according to the code below, which may be found in GeosCore/aerosol_mod.F90. 

       !==============================================================
       ! P A R T I C U L A T E   M A T T E R
       !
       ! See this GEOS-Chem wiki page for the most up-to-date
       ! definitions of PM2.5 and PM10 used in GEOS-Chem:
       !
       ! http://wiki.geos.chem.org/Particulate_Matter_in_GEOS-Chem
       !==============================================================

       ! Particulate matter < 2.5um [kg/m3]
       PM25(I,J,L) = NH4(I,J,L)        * SIA_GROWTH + &
                     NIT(I,J,L)        * SIA_GROWTH + &
                     SO4(I,J,L)        * SIA_GROWTH + &
                     BCPI(I,J,L)                    + &
                     BCPO(I,J,L)                    + &
                     OCPO(I,J,L)                    + &
                     OCPI(I,J,L)       * ORG_GROWTH + &
                     SALA(I,J,L)       * SSA_GROWTH + &
                     SOILDUST(I,J,L,1)              + &   ! + 100% of DST1
                     SOILDUST(I,J,L,2)              + &   !
                     SOILDUST(I,J,L,3)              + &   ! 
                     SOILDUST(I,J,L,4)              + &   ! 
                     SOILDUST(I,J,L,5) * 0.3_fp           ! + 30%  of DST2

       ! Particulate matter < 10um [kg/m3]
       PM10(I,J,L) = PM25(I,J,L) +                    &   ! PM2.5
                     SOILDUST(I,J,L,5) * 0.7_fp     + &   ! + 70%  of DST2
                     SOILDUST(I,J,L,6)              + &   ! + 100% of DST3
                     SOILDUST(I,J,L,7) * 0.9_fp     + &   ! + 90%  of DST4
                     SALC(I,J,L)       * SSA_GROWTH

       ! Include either simple SOA (default) or Complex SOA in
       ! PM2.5 calculation.  In simulations where both Simple SOA and
       ! Complex SOA species are carried (i.e. "benchmark"), then
       ! only the Simple SOA will be added to PM2.5, in order to avoid
       ! double-counting. (bmy, 5/11/18)
       IF ( Is_SimpleSOA ) THEN
          PM25(I,J,L) = PM25(I,J,L) + ( SOAS(I,J,L) * ORG_GROWTH )
          PM10(I,J,L) = PM10(I,J,L) + ( SOAS(I,J,L) * ORG_GROWTH )

       ELSE IF ( Is_ComplexSOA ) THEN 
          PM25(I,J,L) = PM25(I,J,L)                 + &
                        TSOA(I,J,L)   * ORG_GROWTH  + &
                        ASOA(I,J,L)   * ORG_GROWTH  + &
                        ISOAAQ(I,J,L) * ORG_GROWTH        ! Includes SOAGX

          PM10(I,J,L) = PM10(I,J,L)                 + &  
                        TSOA(I,J,L)   * ORG_GROWTH  + &
                        ASOA(I,J,L)   * ORG_GROWTH  + &
                        ISOAAQ(I,J,L) * ORG_GROWTH        ! Includes SOAGX

          ! Need to add OPOA to PM2.5 for complexSOA_SVPOA simulations
          ! -- Maggie Marvin (15 Jul 2020)
          IF ( Is_OPOA ) THEN
             PM25(I,J,L) = PM25(I,J,L) + ( OPOA(I,J,L) * ORG_GROWTH )
             PM10(I,J,L) = PM10(I,J,L) + ( OPOA(I,J,L) * ORG_GROWTH )
          ENDIF
       ENDIF

       ! Apply STP correction factor based on ideal gas law
       PM25(I,J,L) = PM25(I,J,L) * ( 1013.25_fp / PMID(I,J,L) ) * &
                                   ( T(I,J,L)  / 298.0_fp     )

       PM10(I,J,L) = PM10(I,J,L) * ( 1013.25_fp / PMID(I,J,L) ) * &
                                   ( T(I,J,L)   / 298.0_fp    )

Also note that there are some calculations that were not included in the basic definitions of PM2.5 and PM10 in the preceding sections. These are:

Avoid double-counting of ISOAAQ species

Jenny Fisher rightly pointed out that the PM2.5 diagnostic was erroneously including the ISOAAQ species in the accounting of PM2.5 when the Simple SOA option was used. After discussion with the Aerosols Working Group, we modified the PM2.5 and PM10 diagnostic computations accordingly:

To avoid double-counting of SOA, we do the following:

  • When the Complex SOA option is selected, we add TSOA + ASOA + ISOAAQ to the PM2.5 and AOD diagnostics instead the simple SOA species SOAS.
  • Otherwise, we add SOAS to the PM2.5 and AOD diagnostics instead of TSOA + ASOA + ISOAAQ.

NOTE: The GEOS-Chem benchmark simulations carry both Simple SOA and Complex SOA species, but only the Simple SOA species (SOAS) is included in diagnostic output.

Save out PM2.5 diagnostic at STP conditions

Aaron van Donkelaar wrote:

As was originally implemented in GEOS-Chem v11-01, the PM2.5 diagnostic outputs were at ambient conditions. While this is not technically an error, most PM2.5 monitors measure at STP conditions which will cause disagreement during comparison with observations and inconsistency during application of any health response curves (generally determined from the STP observations).
As a result, I’d recommend applying an STP correction factor based on ideal gas law after PM2.5 is calculated:

        PM2.5 = PM2.5 * ( 1013.25 / P ) * ( T / 298 )
        PM10  = PM10  * ( 1013.25 / P ) * ( T / 298 )

--Bob Yantosca (talk) 19:41, 3 November 2021 (UTC)

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