Treating PM2.5 as a "single species" for fine-mode PPM simulation in CMAQ 5.4

Hello everyone!

I am trying to simulate fine mode primary particulate matter (PPM, i.e., without considering the chemical reaction and secondary aerosol formation process and only considering transport, advection, diffusion, and deposition) over Eastern Asia with CMAQ 5.4. As there is not a straightforward method, I am trying some possible ways and inter-comparing their results. Now I am adding an aerosol tracer in the AE namelist, following the instruction from this CMAS forum page Adding Aerosol Tracer. The basic idea is to add a new aerosol species named “NTRA” in the following three files (AE_cb6r5_ae7_aq.nml, CMAQ_Control_DESID_cb6r5_ae7_aq.nml, AERO_DATA.F) assuming that the variable PM2.5 (not including OC and EC) in the gridded-inventory (Named “PMFine2” in my CMAQ-ready inventory) will not react with other gases and aerosols.
Major modifications to files are as follows.

In AE_cb6r5_ae7_aq.nml:

 'NTRA'    ,100.00  ,T     ,T     ,F      ,''     ,''     ,-1    ,''     ,-1     ,'VMASS'     , 1  ,'PRI'         , 1  ,''         ,'Yes'   ,'Yes'   ,'Yes'   ,'Yes'

In CMAQ_Control_DESID_cb6r5_ae7_aq.nml

 ! Region      | Stream Label  |Emission | CMAQ-        |Phase/|Scale |Basis |Op  
 !  Label      |               |Species  | Species      |Mode  |Factor|      |     
   'EVERYWHERE', 'ALL'         ,'PMFINE2','NTRA'        ,'FINE',1   ,' UNIT','a',

In AERO_DATA.F (line 362):

C                                                                                           Visidx_Large
C                                                                               no_M2Wet Tracer        |
C                                                                                       | | Charge      | OM           
C                      Name      T A C Min_Con Density Gas-Name   CTR-Name  Yield Vol   | |   | Visidx  |  |  OptSurr   korg  
C                     ---------- - - - ------- ------- ---------- --------- ----- ----- + +   + ------ --- +  -------- ----- 
     & spcs_list_type('NTRA    ',T,T,F, cm_set, 2200.0, '       ','       ',0.0  ,'NVL',F,T,  0,  0.0, 0.0,F, 'DUST  ', 0.00), ! Newly added tracer

My question is,

  1. Are my steps taken above reasonable enough to realize my goal (3-hourly Primary PM2.5 mass concentration simulation)
  2. If so, how to specify the value of fields “MOLWT” and “AE2AQ SURR” in the AE_cb6r5_ae7_aq.nml if I assume PM2.5 in the inventory as a “species”?

The following files are my log file and preliminary results (NTRA for aitken and accumulation modes respectively).
CTM_LOG_007.v54_intel_2019EastAsia_5_20190529.txt (491.3 KB)

Any comments will be appreciated.


Hi Su,

Sorry for the delay in responding to your thorough post. This approach looks appropriate to me. Have you been successful in getting the wet deposition to work? I don’t think the values of AE2AQ SURR or MOLWT will affect your results very much. You can try using ‘POA’ for AE2AQ SURR since that will be inert in the cloud chemistry routine.

The value of MOLWT matters most if you are using ‘MASS’ for the value of Basis in the emissions rule of your DESID file. Since you are using ‘UNIT’ there will be no conversion based molecular weight, and it should not come into play. Using a nominal value like 100.00 as you have done should be ok.

I would be curious about any additional results or insights you have generated since posting this question.

Best regards,
Ben Murphy

Hello Ben,

Thank you very much for your inspiring reply, which well solved my questions about aerosol parameter settings in CMAQ. Unfortunately, i could not find the simulation result files or the log files because they have been removed two months ago. So it’s hard for me to check whether the wet deposition results were properly created or not then.

As for the Primary PM (PPM) simulation, i have tried another method since then. The basic idea is as follows:

PPM = PM25_tot - PM25_sec

where “PM25_tot” is total PM2.5 concentration (including both primary and secondary aerosol) , while “PM25_sec” is secondary PM2.5 concentration (zero-out all aerosol emissions and only keep gas precursors in the inventory). Both PM2.5 results are directly derived from CCTM_AELMO files.

With your instructions, I’m interested in the consistency of both approaches (i.e., tracer method and the one listed above). I will rerun the previous method and compare both results. I’m very glad to share my results when i have time these days.

Best regards,
Yi Su