Specific meaning of CCTM_ASENS.nc output file in CMAQ-DDM

CMAQ-DDM-3D
1

Hello everyone,
I successfully ran CMAQ5.4-DDM with the following sensinput file configuration. I now have questions about the specific meaning of results under each TSTEP in the CCTM_ASENS.nc file.

Taking the variable O3_TOE as an example, at TSTEP=14, I want to know:

  1. What does each grid cell in the spatial distribution map represent? Specifically, does it indicate the sensitivity of O₃ concentration at TSTEP=14 to TOE at TSTEP=14?

  2. Can DDM calculate the sensitivity of ozone concentration at a specified time to TOE at a different specified time?

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2

Specifically, I want to know what ‘Averaged hourly sensitivities’ means. Any help is grateful.

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3

  1. The spatial distribution indicates the sensitivity of the concentration of species (in your plot O3) resulting from all previous emissions defined by parameter “TOE” (in your case looks like total emissions of NO and NO2).

  2. DDM-3D did have a function to calculate sensitivities to time windowed emissions in the past, but this is currently more easily achieved by splitting out the emissions you want to limit to a different emissions file.

  3. ASENS is the averaged sensitivity across the hour that is analogous to ACONC. It its the sum off all the instantaneous values computed at the sub timesteps (sometimes 5min) divided by the number of the sub timesteps at that hour.

Sergey

4

Hi, Dr. Sergey.
Thanks for your reply.

I’m still not entirely sure about this. If I set the simulation period as August 7 to August 11, 2023, does the spatial distribution result of O₃_TOE at 14:00 on August 11, 2023 represent the sensitivity of O₃ concentration at 14:00 on August 11, 2023 to NOₓ emissions from August 7 up to that moment? I understand this is the hourly average sensitivity. If I aim to calculate the sensitivity of O₃ to NOₓ emissions at a specific moment (e.g., 12:00 on August 9), do I need to isolate/extract only the emissions from that exact time step?

The reason for my clarification is that I need to compare these results with those from CMAQ-adjoint sensitivity calculations. To ensure a valid comparison, I must fully understand the meaning of DDM (Direct Decoupled Method) outputs.

Thank you for your help!

Best regards,

Jiahao

5

Jiahao,

  1. Yes. In the case you describe, the sensitivity fields at 14:00 on August 11th will be the result of all the emissions defined by “TOE” from the beginning of the simulation on August 7th until 14:00 on August 11th.

  2. You will need to do such an emissions extraction/isolation if you want to calculated sensitivity TO emissions that you isolate. DDM-3D provides sensitivity fields of all model species TO specifically defined parameters. When your defined parameters are emissions rates (as they usually are), the sensitivity at any specific time will be to all of the emissions in the defined emissions stream(s). When the emissions streams have isolated hours or regions, it the sensitivity will be to that. When the emissions streams have hourly emissions (which is more common), the sensitivity will be to all of the hours, and also to previous days hours (unless there is a clean restart).

Sergey

2 Likes
6

Hi, Dr. Sergey.

Thanks for your reply.Your answer really helped resolve my confusion.
Thank you very much.

Best regards,
Jiahao