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Guidance Needed: Configuring MAM7 for Aqua Planet Simulation Without Certain

Y

Yinjie Wang

Yinjie Wang
New Member
Dear CESM Community,

I am currently working on an aquaplanet simulation using CESM, and I would like to disable specific land-based aerosol modes while using MAM7. The aerosol modes I want to remove are as follows:

  • Primary carbon
  • Fine dust
  • Coarse dust
However, I still want to keep sea salt aerosols active.

I have tried modifying the user_nl_cam file by adjusting the &chem_inparm, mode_defs, and rad_climate settings within the atm_in file, but I encountered errors during runtime.

Could you please help me with the following:

  1. How should I configure the relevant aerosol modes and parameters in user_nl_cam to disable these specific aerosol types?
  2. Are there any additional dependencies or specific configurations in the mode_defs or rad_climate sections that I need to address?
  3. Are there any examples or documentation available that explain how to disable these particular aerosol modes in MAM7?
Your help would be greatly appreciated.
 
R

rrbuchholz

Rebecca Buchholz
CSEG and Liaisons
Staff member
Hi Yinjie,

Primary carbon can be removed/ignored by not setting a pointer to bc_a4 and pom_a4 in the user_nl_cam
under:
ext_frc_specifier and srf_emis_specifier

Dust emissions are an interactive component in CAM, so you will need to disable the dust module.

Once the emissions are off for those species, then you shouldn't need to do anything else.

Hope that helps.
Best,
Rebecca
 
D

Danny Leung

New Member
Hi Yinjie-
To get rid of fine dust and coarse dust, you can do it in the user_nl_cam (or in the source code).
In user_nl_cam, dust_emis_fact is a global tuning parameter (typically = 0.8) that scales inversely with total dust emissions. To scale dust emissions to basically zero, you can set a very big value like
dust_emis_fact = 10000.0D0
and you will get rid of dust emissions and thus dust. Then, there is no need to touch upon mode_def and rad_climate.
Hope this helps!
Danny
 
Y

Yinjie Wang

Yinjie Wang
New Member
rrbuchholz said:
Hi Yinjie,

Primary carbon can be removed/ignored by not setting a pointer to bc_a4 and pom_a4 in the user_nl_cam
under:
ext_frc_specifier and srf_emis_specifier

Dust emissions are an interactive component in CAM, so you will need to disable the dust module.

Once the emissions are off for those species, then you shouldn't need to do anything else.

Hope that helps.
Best,
Rebecca
Click to expand...
Hi Rebecca,

Thank you very much for your helpful reply! I understand I need to remove the pointer to bc_a4 and pom_a4 in user_nl_cam. However, I’m wondering what exact value I should set them to if I don’t want the model to read those fields at all.

I’ve tried:

  • Leaving the string blank (e.g., ''),
  • Using 'none',
  • Using 0,
but none of these seem to be recognized by the model. Could you please clarify the exact way to remove bc_a4 and pom_a4 pointers, so that CAM does not look for their input files and does not crash?

Thanks again for your help!

Best,
Yinjie
 
Y

Yinjie Wang

Yinjie Wang
New Member
rrbuchholz said:
Hi Yinjie,

Primary carbon can be removed/ignored by not setting a pointer to bc_a4 and pom_a4 in the user_nl_cam
under:
ext_frc_specifier and srf_emis_specifier

Dust emissions are an interactive component in CAM, so you will need to disable the dust module.

Once the emissions are off for those species, then you shouldn't need to do anything else.

Hope that helps.
Best,
Rebecca
Click to expand...
Hi Rebecca (and CESM Community),

Thank you for clarifying how to remove bc_a4 and pom_a4 by not setting pointers to them in ext_frc_specifier and srf_emis_specifier. However, I’ve noticed that if I completely leave them out, CESM seems to revert to defaultemission files for black carbon and primary organic matter. This suggests that the default configuration (coming from the compset or the chemical mechanism) is still pointing to those species behind the scenes.

Could you please clarify how to override or clear the default emissions so that bc_a4 and pom_a4 truly do not get read at all (i.e., the model does not look for them and does not crash)?

Here are some specific questions:

  1. If I omit any mention of bc_a4 and pom_a4 in user_nl_cam, will the model still load their emissions from a default source?
  2. Is there a recommended way to “clear” or “turn off” default emission settings, short of explicitly specifying a custom list for every species I do want to keep (like sea salt, SO2, etc.)?
  3. If the best practice is indeed to explicitly list all the species I want to include in my user_nl_cam (thus excluding bc_a4 and pom_a4), could you point me to any official example or documentation? I want to ensure I’m not missing any hidden settings that might still load black carbon or organic carbon by default.
Thanks again for your help!
Best,
Yinjie
 
R

rrbuchholz

Rebecca Buchholz
CSEG and Liaisons
Staff member
Hi Yinjie,

In case you haven't found it, the Chemistry Modeling Wiki is here: Home - CAM-Chem - wiki.ucar.edu
Additionally, tutorial material is here: Atmospheric chemistry — CESM Tutorial

In regards to your question, removing them from the emission description/pointer should work. You do not set them to zero, or anything else, you just remove the line. For example, if you have
...
'XYLENES -> /glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/chem/emis/CMIP6_emissions_1750_2015/emissions-cmip6_XYLENES_anthro_surface_1750-2015_0.9x1.25_c20170608.nc',
'XYLENES -> /glade/campaign/acom/MUSICA/emis/qfed/qfed2.5_finn/f09/qfed.emis_XYLENES_0.9x1.25_mol_2000_2022.nc ',
'bc_a4 -> /glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/chem/emis/CMIP6_emissions_1750_2015/emissions-cmip6_bc_a4_anthro_surface_1750-2015_0.9x1.25_c20170608.nc',
'bc_a4 -> /glade/campaign/acom/MUSICA/emis/qfed/qfed2.5_finn/f09/qfed.emis_bc_a4_0.9x1.25_mol_2000_2022.nc ',
'DMS -> /glade/campaign/acom/MUSICA/emis/qfed/qfed2.5_finn/f09/qfed.emis_DMS_0.9x1.25_mol_2000_2022.nc ',
'DMS -> /glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/chem/emis/CMIP6_emissions_1750_2015/emissions-cmip6_DMS_other_surface_1750-2015_0.9x1.25_c20170322.nc',
...
Click to expand...
this would become
...
'XYLENES -> /glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/chem/emis/CMIP6_emissions_1750_2015/emissions-cmip6_XYLENES_anthro_surface_1750-2015_0.9x1.25_c20170608.nc',
'XYLENES -> /glade/campaign/acom/MUSICA/emis/qfed/qfed2.5_finn/f09/qfed.emis_XYLENES_0.9x1.25_mol_2000_2022.nc ',
'DMS -> /glade/campaign/acom/MUSICA/emis/qfed/qfed2.5_finn/f09/qfed.emis_DMS_0.9x1.25_mol_2000_2022.nc ',
'DMS -> /glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/chem/emis/CMIP6_emissions_1750_2015/emissions-cmip6_DMS_other_surface_1750-2015_0.9x1.25_c20170322.nc',
...
Click to expand...
You will need to include all the other emissions in your user_nl_cam namelist changes. You can find the default pointers in your CaseDocs/atm_in file under the headings "srf_emis_specifier" and "ext_frc_specifier" (don't change anything in that folder/file, but you can see how the default settings are implemented).

An example of some emission forcing pointers for a certain run are here in this tutorial exercise (in the answers section):
But I would recommend looking at the default version of your own run, to make sure it is consistent with your setup.

Hope that Helps!
Best,
Rebecca
 
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