Photolysis of NO2 in SAPRC07

Dear CMAQ forum,

I am using saprc07tc_ae6_aq in CMAQv5.2. In my recent simulation for the summer season, surface ozone concentrations were calculated very low. In that simulation, I used emissions data that had shown reasonable results in the past.

I checked PHOTODIAG2 and found that NO2_06 was almost zero, as shown in the attached. So, I thought that NO2 photolysis was not calculated. Does anyone know about the reason for this NO2_06 to be zero?

Appreciate your kind help.

I cannot identify what is causing the problem. Perhaps, examining other variables in the PHOTDIAG1 file may give clues on the cause (such as COSZENS, ETOT_SRC_W381, OZONE_COLUMN, TRANS_DIRECT, TAU_TOT_W381, TAU_CLOUD_w381, TRANS_DIFFUSE, and AOD_W381).

The below plots show possible ranges of their values over the northern hemisphere.


Please post the contents of the CCTM_v52.cfg file.
When you previously obtained reasonable results with this emissions dataset, what version of the model were you using?
Do the values of NO2_O6 increase significantly later in the day, or aloft?


Dear Chris,

Thank you for your comment. I am attaching the cfg file. I cannot see any diurnal variation in NO2_06, but the top level has some value. I used the same V5.2 for the previous calculation.

Thank you for your cooperation on it.

CCTM_v52.cfg.txt (3.1 KB)

Thank you very much for your very useful advice. I will check it out as soon as possible. I will report back as soon as I find out something.

Thank you for your cooperation on it.

I have run CMAQv5.4 with the saprc07tc_ae6_aq chemical mechanism. That has generated larger values of NO2_06.
CMAQv5.2 was released in June 2017, over 6 years ago. It is difficult to reconstruct a platform on which to test such an old version of the code. Is there a compelling reason why you need to run using version 5.2?

Thank you for your comment on it. I understand that upgrading the version may be one of the quickest solution.

I wanted to perform the long term calculation under the same conditions as much as possible without changing the calculation environment.

I will consider upgrading the CMAQ in the future.