Replacing the Dust Aerosol Online Calculation with Emission Data Yielded Significantly Different Outcomes.

[CaliFornia]

I am running simulation with CESM2.1.4. The model uses MAM4 to calculate aerosol number concentration and mass concentration.

What I want to do:
Simulation 1: output the emission flux of dust (both number and mass flux)
Simulation 2: read in the (daily) output of dust number and mass flux from Simulation 1, instead of online calculation.

What I expect:
Similar results of number and mass concentrations of dust between the two simulations.

What I did:
Simulation 1: I modified the aero_model.F90 and run a 10-year simulation with F2010Climo composet, and output the mass and number emission flux for dust.
Simulation 2: Then I disabled the calculation of them (by commenting out 'call dust emis'), and in the user_namelist add the output from simulation 1 as emission files.

What I get:
Very different result between the two simulations, such as the dust concentration during the first 12 months:


Any ideas on why is that? I appreciate any comments.

 

[rrbuchholz]

Hi there!

Did you check that the CESM defined surface fluxes of dust matched your files you were saving by modifying aero_model_F90?
The variables for example to save would be: SFdst_a3

Also, what is the temporal resolution of your emission flux files - they may differ from the "online" time resolution.

Best,
Rebecca

 

[CaliFornia]

Hi there!

Did you check that the CESM defined surface fluxes of dust matched your files you were saving by modifying aero_model_F90?
The variables for example to save would be: SFdst_a3

Also, what is the temporal resolution of your emission flux files - they may differ from the "online" time resolution.

Best,
Rebecca

Hi Thank you so much for your response!

1. I did named the variable 'SFdst_a3' in the emission file before put it into the srf_emis_specifier section in the namelist.
2. I output this variable with avgflag_pertape = 'A'; mfilt = '1'; nhtfrq = '-24'.
So the time resolution of the file will be daily, with time_bnds set to 2010.
I am using F2010Climo, and the srf_emis_type = 'CYCLICAL', and I am not sure if I can use the daily emission. I think the emission file will be interpolated by the model right? And the emission data are flux in (molecules/cm2/s), time resolution should not be a problem I guess:


3. I am so confused why the mass concentration and number concentration can be so different (about ~100 times different) when surface flux are so close: