Expected seasonal CMAQ Ozone production based on Process Analysis

I defined IRR_OUTPUT O3prod = NETP[O3]; in the Process Analysis input file read by CMAQ 5.3.3 run script. In the CMAQ user guide, I see NETP[O3] being defined as sum of O3 from all reactions where species O3 is a product but only using reactions where net production is greater than zero. When I compare the O3prod variable (actually the average of diurnal concentrations of O3prod multiplied by 1000 to get ppb values) of CCTM_IRR* files for Feb, July and Oct months in a gridcell near Nevada at the lowest layer, I am seeing higher production of O3 in Feb than in July during sunny hours:


The late start of O3 production in Feb (at 15:00:00 UTC vs at 13:00:00 UTC in July) and earlier fall of winter O3 production during the day looks right to me. I am just unsure that higher sunny hour O3 production in Feb than in July is correct though.

Just for reference, the single gridcell whose O3 net production is plotted above is circled in red below:

I’m not certain the following explains your observation but may be information does. PROD[ O3 ] sums all reactions where ozone is a product but NETP[ O3 ] corrects production for reactions where ozone is both a reactant and product.

To illustrate the difference, examine the below extract from the process analysis report file written to the output directory. (The cb6r3_ae7_aq mechanism was used.) In the extract, PROD[ O3 ] include five reactions where ozone has zero net production.

   cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
          Summary of Input IRR Commands for OUTPUT : O3PROD
   cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc

         The IRR_OUTPUT command was specified as follows:

             IRROUT(  4) =             PROD [O3]

    cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc

         The referenced operators are defined as follows:

        c..Production of O3
            PROD(  1) =
             &  +           IRR<    R2> ! O+M+O2=O3
             &  +  0.1500 * IRR<   R57> ! C2O3+HO2=.41*PACD+.15*AACD+.15*O3
                                         !      +.44*MEO2+.44*RO2+.44*OH
             &  +  0.1500 * IRR<   R65> ! CXO3+HO2=.41*PACD+.15*AACD+.15*O3
                                         !      +.44*ALD2+.44*XO2H+.44*RO2+.44*OH
             &  +  0.1500 * IRR<  R210> ! OPO3+HO2=.41*PACD+.15*AACD+.15*O3
                                         !      +.44*ALDX+.44*XO2H+.44*RO2+.44*OH
              &  +           IRR<  SA08> ! SESQ+O3=O3+SESQRX
              &  +           IRR<   T11> ! BUTADI+O3=O3+.52*ACROLE
              &  +           IRR<   T14> ! ACRO_P+O3=O3
              &  +           IRR<   T18> ! ACROLE+O3=O3
              &  +           IRR<   HG1> ! HG+O3=.5*HGIIAE+.5*HGIIGA+O3

    cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
              Summary of Input IRR Commands for OUTPUT : O3NET_PROD
     cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc

           The IRR_OUTPUT command was specified as follows:

           IRROUT(  3) =             NETP [O3]

       cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc

                  The referenced operators are defined as follows:

        c..Net production of O3
                  NPRD(  1) =
             &  +           IRR<    R2> ! O+M+O2=O3
             &  +  0.1500 * IRR<   R57> ! C2O3+HO2=.41*PACD+.15*AACD+.15*O3
                            !      +.44*MEO2+.44*RO2+.44*OH
             &  +  0.1500 * IRR<   R65> ! CXO3+HO2=.41*PACD+.15*AACD+.15*O3
                            !      +.44*ALD2+.44*XO2H+.44*RO2+.44*OH
             &  +  0.1500 * IRR<  R210> ! OPO3+HO2=.41*PACD+.15*AACD+.15*O3
                            !      +.44*ALDX+.44*XO2H+.44*RO2+.44*OH

Thanks @bhutzell for your clarification. Do you think I should only keep track of the reaction

<    R2> ! O+M+O2=O3

in CMAQ’s Process Analysis to record the O3 production in my simulation? In theory, above reaction is the only reaction that produces O3 in the atmosphere, but then in a condensed chemical mechanism like CB6_AE7_AQ, there are other reactions like

<   R57> ! C2O3+HO2=.41*PACD+.15*AACD+.15*O3 +.44*MEO2+.44*RO2+.44*OH
<   R65> ! CXO3+HO2=.41*PACD+.15*AACD+.15*O3 +.44*ALD2+.44*XO2H+.44*RO2+.44*OH
<  R210> ! OPO3+HO2=.41*PACD+.15*AACD+.15*O3 +.44*ALDX+.44*XO2H+.44*RO2+.44*OH

that produce O3 as well.