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

 

[Rakesh]

Thats a very detailed description of pcg, thakns for sharing Yifan!
I have doubts about this; please see if you can help with this. In emission driver of SAPRC-MOSAIC-VBS the pcg inputs were written and taken from orgi_bb or orgj_bb for biomass burning and orgi_a for anthropogenic. These input as the calculation looks like this should be the organic mass fraction of biomass and anthropogenic activity. (1) So these inputs we will take from OC or NMVOC?
(2) also the ratio does match with the Shrivastava 2 bins but the actual number in the paper was 1 and 6.5 but they used 1.17 and 7.605.
Please see