Clarification on PM2.5 speciation in simple SOA vs complex SOA with SVPOA schemes #2511
Comments
yantosca
added
topic: Aerosols
|
Hi Tessa, I haven't run the complex OA code myself, but of somewhat familiar with it. Looking at Sid Pai's paper (https://acp.copernicus.org/articles/20/2637/2020/), EPOA should be the emitted POA (OPOA is if the emitted POA and POG gets oxidized). I'm not sure why EPOA isn't in the lines of code you gave. Is it already in the PM2.5 prior to adding in TSOA etc? Jeff |
|
Hi Jeff, thank you for your response and for sharing this paper by Sid Pai! According to the paper, in the simple scheme "The EPOA and OPOA species are represented within the GEOS-Chem model using the variable names OCPO and OCPI, respectively." This is consistent with the definition of PM2.5 in the aerosol_mod, excerpt of which is included below for reference. However, the definition of primary OA in the complex scheme still seems a bit unclear to me. It is my understanding that Pai used EPOA and OPOA to calculate total POA ("As in the simple scheme, the EPOA and OPOA are assumed to have an OM:OC ratio of 1.4 and 2.1, respectively. ") but I am not sure what EPOA is called in the complex scheme, as there are no species called "OCPO" that are produced in complex SOA. The wiki link in the aerosol_mod code for PM calculation is broken so I am unsure where to look for additional information. ` !============================================================== ` |
|
Hi Tessa, OCPO is part of the first PM2.5 calculation in the code you pasted. It wouldn't be produced in the complex SOA scheme since it's only emitted, not chemically produced. Or maybe I'm not understanding you correctly? Jeff |
|
Hi Jeff, Thanks for your reply and apologies for the confusion--I think I am also confused. In the paper by Pai, it stated when describing the simple SOA scheme that EPOA is represented in the model as OCPO (There is no variable named EPOA and when you search the code for it nothing shows up). Where I am getting confused is in the description of the complex scheme, where nothing is called OCPO but in the description of the complex model it states that primary OA has an EPOA and OPOA component, and there is a species in AerosolMass called OPOA, but I don't see anything called EPOA. "The complex scheme, based primarily on Pye et al. (2010) and Marais et al. (2016), is graphically described in Fig. 1. The primary organics are treated as semi-volatile and allowed to reversibly partition between the aerosol (EPOA) and gas (EPOG) phase using a two-product reversible partitioning model while simultaneously undergoing oxidation with OH in the gas phase to form oxidized primary organic gases (OPOGs) that, in turn, reversibly partition to oxidized primary organic aerosols (OPOAs)." So I am trying to calculate total primary organic aerosols in the complex scheme, and just unsure what to include in the calculation. I know AerMass_OPOA should be included but not sure how to represent the EPOA fraction. Is this the AerMass_POA metric? In the ReadtheDocs, POA is described as "aerosols from SVOCs". |
|
Hi Tessa, I'm confused about OCPO not being part of AerMass. The code that you included in the first post from this morning includes "State_Chm%AerMass%OCPO(I,J,L)". (Again, my group doesn't generally run the complex scheme, and I haven't personally dug into the code in a while... the sad progression of professors :/) |
|
Hi @tessac2, I am not an expert in aerosol but I did some research about Regarding your question about geos-chem/GeosCore/aerosol_mod.F90 Lines 502 to 511 in bef56c6 To calculate primary OA for |
|
Thank you! I'm glad to have a serious complexSOA user/contributer weigh in! |
|
Thank you @theloniuspunk and @yuanjianz ! @yuanjianz thank you for your detailed explanation. Would AerMass_OPOA take into account hygroscopic growth or would it be just an issue with the POA? Following your calculation: 'Primary OA = EPOA+OPOA(?)*ORG_GROWTH'. Do you know if there something that is double counted by calculating the Primary OA this way? I just wanted to clarify the question mark. I also am a bit confused by some aspects of the diagnostics_mod.F90 in regards to this. In the sum of organic aerosol for TotalOA there is OCPO, OCPI and OPOA. Does this mean OPOA/OCPI are double counted in TotalOA for the complex scheme? Additionally, for total organic carbon it seems like it either takes into account POA or OPOA based on the IF (Is_POA) ELSE IF (Is_OPOA), but I could be misinterpreting? |
|
Hi @tessac2, for your three quesions:
I think AerMass diagnostics don't account for hygroscopic growth except for PM25.
I put the question mark here because I am not an expert in aerosol chemistry that I am not sure if OPOA is a component of primary OA. As for the double counting, maybe @theloniuspunk may have better insights.
This part's logic is clarified and simplified in my fix in #2315. See diagnostics_mod.F90 fix.
|
Your name
Tessa Clarizio
Your affiliation
University of Illinois Urbana-Champaign
Please provide a clear and concise description of your question or discussion topic.
Model details
GCClassic v14.3.1
MERRA-2
Nested grid over North America (0.5 x 0.625)
Full chemistry
Standard OR Complex SOA with SVPOA
47 vertical levels
compiler: gcc 9.3.0
Questions
Additional details/context
Hello! I am interested in comparing the PM2.5 speciation between Standard and Complex SOA. I understand how to do this for simple SOA, where I calculate as follows (where the species concentrations have been adjusted by their molecular weight/volume of 1 mole air at standard temp and pressure to get the same units of ug/mol):
PM2.5 = AerMass_NH4*SIA_GROWTH + AerMassNIT*SIA_GROWTH + AerMassSO4*SIA_GROWTH + AerMassHMS*SIA_GROWTH + (SpeciesConcVV_BCPI + SpeciesConcVV_BCPO) + (SpeciesConcVV_OCPI *ORG_GROWTH+ SpeciesConcVV_OCPO)*2.1 + SpeciesConcVV_DST1 + SpeciesConcVV_DST2*0.30 + SpeciesConcVV_SOAS*ORG_GROWTHThis is based on the GEOS-Chem code as well as this wiki page (which I know is a bit out of date since it does not have HMS): https://wiki.seas.harvard.edu/geos-chem/index.php/Particulate_matter_in_GEOS-Chem. This lets me calculate the speciation and get a pie chart along the lines of:
Where OA is primary organic aerosol (from OCPI and OCPO) and SOA is secondary organic aerosol (from SOAS).
However, it seems less clear to me what is included in the SOA and primary OA in the PM2.5 calculation for the complex SOA scheme with SVPOA.
According to the aerosol mod code,
However, there is no species AerMassISOAAQ. I see in aerosol mod, the ISOAAQ is calculated as follows:
Therefore I have included SOAGX, SOAEI, and LVOCOA in the calculation of ISOAAQ, and calculated SOA as:
SOA = AerMassTSOA*ORG_GROWTH + AerMassASOA*ORG_GROWTH + (AerMassSOAGX + AerMassSOAEI + AerMassLVOCOA)*ORG_GROWTHHowever, I am a bit confused what is primary OA.
In the aerosol mod code, I see:
So I initially though OPOA could be the primary organic aerosol. But according to the readthedocs , the OPOA is aerosols products of POG oxidation, which makes me think it is hydrophilic only? I see there is another species called AerMassPOA which is described as aerosols from SVOCs. In issue #2315 it seems OPOA is included in the ComplexSOA_SVPOA calculation. It seems from #384 that perhaps there was debate whether OPOA should be included in SOA or POA and that may be why it is separate?
So I was just hoping (1) to clarify how to calcuate SOA and primary OA that are included in the PM2.5 calculation, and (2) propose either a feature where these diagnostics are made a bit clearer in the future, or more clarification on the History diagnostics page on ReadTheDocs, as many of the wiki links cited in previous issues no longer work.
Thanks! :)
@beckyalexander @theloniuspunk @wporter
The text was updated successfully, but these errors were encountered: