What are the definition of pcg1_b_c, pcg1_f_c etc

[onishi]

Dear All

I am trying to understand the variables used for biomass emissions.
In chem/emissions_driver.F, we have the following lines

chem(i,k,j,p_pcg1_b_c) = chem(i,k,j,p_pcg1_b_c) &
+(emis_ant(i,k,j,p_e_orgi_bb)/1.57+emis_ant(i,k,j,p_e_orgj_bb)/1.57)*conv3*1.17
chem(i,k,j,p_pcg2_b_c) = chem(i,k,j,p_pcg2_b_c) &
+(emis_ant(i,k,j,p_e_orgi_bb)/1.57+emis_ant(i,k,j,p_e_orgj_bb)/1.57)*conv3*7.605
chem(i,k,j,p_pcg1_f_c) = chem(i,k,j,p_pcg1_f_c) &
+(emis_ant(i,k,j,p_e_orgi_a)/1.25+emis_ant(i,k,j,p_e_orgj_a)/1.25)*conv3*1.17
chem(i,k,j,p_pcg2_f_c) = chem(i,k,j,p_pcg2_f_c) &
+(emis_ant(i,k,j,p_e_orgi_a)/1.25+emis_ant(i,k,j,p_e_orgj_a)/1.25)*conv3*7.605
chem(i,k,j,p_pcg1_b_o) = chem(i,k,j,p_pcg1_b_o) &
+(emis_ant(i,k,j,p_e_orgi_bb)/1.57+emis_ant(i,k,j,p_e_orgj_bb)/1.57)*conv3*0.40
chem(i,k,j,p_pcg2_b_o) = chem(i,k,j,p_pcg2_b_o) &
+(emis_ant(i,k,j,p_e_orgi_bb)/1.57+emis_ant(i,k,j,p_e_orgj_bb)/1.57)*conv3*2.60
chem(i,k,j,p_pcg1_f_o) = chem(i,k,j,p_pcg1_f_o) &
+(emis_ant(i,k,j,p_e_orgi_a)/1.25+emis_ant(i,k,j,p_e_orgj_a)/1.25)*conv3*0.08
chem(i,k,j,p_pcg2_f_o) = chem(i,k,j,p_pcg2_f_o) &
+(emis_ant(i,k,j,p_e_orgi_a)/1.25+emis_ant(i,k,j,p_e_orgj_a)/1.25)*conv3*0.52

1. What does 'pcg' stand for?
2. Is it correct that '_b_' and '_f_' are for biomass and fossil, and '_c_' and '_o_' are for C and O components, respectively?
3. All the coefficients at the end (1.17, 7.605, 0.40, etc). What are they and how are they calculated?

I have been searching for the answers to these question on internet for a long time,
But I have not been able to find any.
Can anyone explain what they are? and maybe give me some references these calculations are based on?

I really appreciate if I can get some info on these questions.

Thank you in advance,
Tatsuo

 

[Wendy Liu]

Hi onish,
I chose the SAPRC-MOSAIC-vbs2(198) and got these variables in the wrfout too. Do you find out what are they now? Could you please share with me? Thanks!
Wenyu

 

[Yifan]

Hi onish and Wenyu,
I ran into this problem when looking at the WRF source code WRF/chem/module_mosaic_therm.F and WRF/chem/module_data_mosaic_therm.F, too. The name pcg1_b_o is really confusing. I took a whole night to go through the relevant papers and source code, and here are some of my inferences and corresponding evidence.

1. A paper about this:
   • Sect. 2.1mentions that POA has been described by 9 surrogate species with C* values (at 298K and 1atm) of 0.01, 0.1, 1, 10, 100, 1000, 10000, 100000, 1000000µg m^−3. POA species have also been segregated by two emissions sectors: biomass burning and anthropogenic (predominately fossil fuel), and separated by oxygen and non-oxygen (C, H, N) components in order to allow calculating O:C ratios for the modeled OA.
   • Besides POA species, there are also SI-SOA species. SI-SOA refers to SOA formed due to photochemical oxidation of all Semi-Volatile Organic Compounds(SVOC)/Intermediate Volatility Organic Compounds(IVOC) precursors. SI-SOA species are described by 8 oxidized volatility species due to lower-volatility.
2. In the code chem/module_data_mosaic_therm.F., vapor pressures of soa species are calculated by function fn_po(po_298, dh, t). Form po_soa(ipcg1_b_c_g) to po_soa(ipcg9_b_c_g), the value assigned to po_298 grows in multiples of 10. And the value assigned to dh is consistent with delta Hvap in Table 2 of the paper mentioned above.
3. When VBS was first introduced to WRF/chem/module_data_mosaic_therm.F 15 years ago, there were comments written in its code :

[SIZE=4] do i=1,9[/SIZE]
flagsoap(i)=1 ! Biomass burning(carbon and oxygen species) +traditional soa species
enddo
[SIZE=4] ! flagsoap determines if the species 'i' is fresh (flagsoap(i)=2) or aged(flagsoap(i)=1[/SIZE]
Based on the above evidence. I think that 'pcg' stands for POA, pcg1 has the lowest volatility and the pcg9 has the highest. '_b' and '_f' are for biomass and fossil. '_o' and '_c' are for oxygen and non-oxygen. 'opcg' might stand for SI-SOA
The above is my inference, if there is improper welcome to discuss!
Thanks!
Reference: Shrivastava, M., Fast, J., Easter, R., Gustafson Jr., W. I., Zaveri, R. A., Jimenez, J. L., Saide, P., and Hodzic, A.: Modeling organic aerosols in a megacity: comparison of simple and complex representations of the volatility basis set approach, Atmos. Chem. Phys., 11, 6639–6662, https://doi.org/10.5194/acp-11-6639-2011, 2011.
Old code for WRF/chem/module_data_mosaic_therm.F : https://github.com/wrf-model/WRF/commit/da830291195c8952baec00cd2ffa666e69b0022c?diff=split&w=0#diff-82354acb14c5dba661aa2b97b621962c416f9a5b86662a6e55093f53b049e1b6