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transient volcano forcing in WACCM


We are trying to run a single forcing case using an 1850 compset and then letting only volcanoes go through their transient 20th Century forcing. We need to know which namelists to modify? Is the sad_file in the chem_inparm namelist the only file we need to modify or are other files involved in volcano forcing for WACCM (like prescribed_aerosols)?Thanks


CSEG and Liaisons
Staff member
The sad_file is the only thing that you would change. It prescribes surface area density of stratospheric aerosols for chemistry, which is also converted to mass for radiative calculations. The other prescribed aerosols in the namelist are tropospheric aerosols for prescribed BAM in WACCM4.
Is the volcanic eruption database from Mills et al 2015 included in WACCM for CESM2? If so, which nc file is it in? If not, is that file available and how do I tell WACCM to use it, or do I need to program it myself from the supplementary data xlsx spreadsheet with the paper?

I set up a case with the BWHIST compset and looking at the atm_in file in the run directory under &chem_inparm I only see references to continuous volcanic emissions not eruptions, and I don't see any references to SAD either.


CSEG and Liaisons
Staff member
Yes, an updated version of the database from Mills et al., 2016 is included in the historical WACCM6 compsets (BWHIST, FWHIST, FWSD, BWmaHIST, FWmaHIST, FWmaSD) in CESM2.

You should see an SO2 emission file starting with "VolcanEESM" in the ext_frc_specifier of your atm_in namelist, i.e.:

'SO2 -> /glade/p/cesmdata/cseg/inputdata/atm/cam/chem/stratvolc/VolcanEESMv3.11_SO2_850-2016_Mscale_Zreduc_1deg_c180812.nc',

Aerosol surface area density (SAD) is no longer prescribed in WACCM6, as it was in WACCM4. It is calculated from the prognostic aerosols, which evolve based on emissions.
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