Attempt to apply dry deposition species to photolysis reactions

CMAQ
1

Hi all,

I’m using CMAQ v5.3.2 and m3dry module for dry deposition. What I want to do is getting the concentration or dry deposition velocity of nitrate from m3dry or other modules control dry deposition, then considering it a reactant of a new heterogeneous photolysis reaction I added in mech.def.

I have checked that DEPVVARS.F has NO3 in DEPSPC, that probably means I don’t need to add new species in dry deposition modules. Instead, I might have to add a new species "dNO3" to represent dry deposited nitrate in AE_cb6r3m_ae7_kmtbr.nml.

The problem is I have no idea about how to get dNO3 concentration or production rate from m3dry which is needed to the calculation in mech.def. And assume that I get dNO3, what should I do to add it into AE_cb6r3m_ae7_kmtbr.nml like ANO3I or ANO3J species. I guess that m3dry and EmissCtrl.nml need to be connected in some way.

If you have any suggestion or better solution, please let me know. Big thanks to your help.

Liu

2

Maybe I’m being too verbose. In short, there is a new heterogeneous photolysis reaction I want to add in mech.def. The reactant is only dry deposited nitrate, both reaction rate and the product species are available in CMAQ now. My plan is to add new species dNO3 to AE_cb6r3m_ae7_kmtbr.nml, but I don’t know how to link dNO3 with m3dry.

3

I do not quite follow what it is you are trying to do.
First, the amount of nitrate that is removed via dry deposition is already calculated by m3dry and is output in the DRYDEP file. The deposition velocity is also available as an output, if you set the VDIFF_DIAG environment variable. You can examine the write statements to those files to track the arrays that are written and find the values you want to manipulate.
Second, be advised that mech.def is not directly read by the CMAQ chemical transport model. It is processed by the CHEMMECH utility. See this tutorial.

4

Hi Chris,
Thanks for your reply. As you said, hourly dry deposition value is available in DRYDEP output file. For the deposition velocity, maybe you want to say CTM_DEPV_FILE environment variable in runscript.
I want to add this reaction in mech.def by CHEMMECH tool,

< R224 > dNO3 = 0.67 * HONO + 0.33 * NO2 # 48.57*k< R47 >

Here dNO3 means accumulated dry deposited nitrate before rain event, so I hope to find the code calculating dry deposition value.

I notice that m3dry can output pvd variable and its unit is ppm * m/s, does it means deposition velocity?

As for how to judge rain event, I plan to use met data in ASX_DATA module.

5

You are correct, I meant to set the CTM_DEPV_FILE environment variable to Y to turn on the CCTM_DEPV outputs.

6

Hi Chris,

What I want to do is add a photolysis reaction above, and the reactant is dry precipitation NO3 calculated by the model. I have found the dry deposition rate and amount of the model output files, but I want to use them online to calculate additional HONO and NO2 following R224 in the model.

So the problem I’m facing now is to get dNO3 and use it online. And, trickier still, it may involve unit conversion.