Scaling factor for aerosol optical depth in CAM 6

[tc_chakraborty@yale_edu]

 In CAM 3, it was possible to add a scaling factor for aerosol mass using SCL_RF options. I was wondering if there is any way to do this in CAM 6. I was also wondering if it is possible to scale aerosol optical depth instead of the mass. Ideally, I would want to do this with radiation diagnostics, so that other variables (surface meteorology, clouds, etc.) remain identical.

 

[mmills]

While I am not familiar with how aerosols were handled in CAM3, I assume it used the bulk aerosol model (BAM) in either prognostic or prescribed mode. In CAM6, aerosols are prognostic and calculated in the modal aerosol model (MAM) based on emissions. It sounds like what you want to do is to add a second radiation call for the purpose of outputting diagnostics without aerosols. To do this, look at the rad_climate line in your atm_in namelist for CAM6:

 rad_climate        = 'A:Q:H2O', 'N:O2:O2',
         'N:CO2:CO2', 'N:ozone:O3',
         'N:N2O:N2O', 'N:CH4:CH4',
         'N:CFC11:CFC11', 'N:CFC12:CFC12',
         'M:mam4_mode1:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam4_mode1_rrtmg_aeronetdust_sig1.6_dgnh.48_c140304.nc',
         'M:mam4_mode2:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam4_mode2_rrtmg_aitkendust_c141106.nc',
         'M:mam4_mode3:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam4_mode3_rrtmg_aeronetdust_sig1.2_dgnl.40_c150219.nc',
         'M:mam4_mode4:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam4_mode4_rrtmg_c130628.nc',
         'N:VOLC_MMR1:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/volc_camRRTMG_byradius_sigma1.6_mode1_c170214.nc',
         'N:VOLC_MMR2:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/volc_camRRTMG_byradius_sigma1.6_mode2_c170214.nc',
         'N:VOLC_MMR3:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/volc_camRRTMG_byradius_sigma1.2_mode3_c170214.nc'

Then set up a diagnostic call using rad_diag with aerosol modes removed:

rad_diag_1 = 'A:Q:H2O', 'N:O2:O2',
         'N:CO2:CO2', 'N:ozone:O3',
         'N:N2O:N2O', 'N:CH4:CH4',
         'N:CFC11:CFC11', 'N:CFC12:CFC12',
         'N:VOLC_MMR1:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/volc_camRRTMG_byradius_sigma1.6_mode1_c170214.nc',
         'N:VOLC_MMR2:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/volc_camRRTMG_byradius_sigma1.6_mode2_c170214.nc',
         'N:VOLC_MMR3:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/volc_camRRTMG_byradius_sigma1.2_mode3_c170214.nc'

If you want, you can also remove the prescribed volcanic aerosols in this call, or add a third radiation call with rad_diag_2.

Outputs from rad_diag_1 have _d1 appended, i.e.: FSNT_d1, QRS_d1, SWCF_d1, etc.