CMIP6 volcanic forcing

Code and installation

The CMIP6 volcanic forcing implementation has been committed to both the noresm (CESM1.2) and the noresm-dev (CESM2_beta) repository. The commits can be viewed here:
https://github.com/metno/noresm/commit/59d2b4c4714c0df41141a10d79fd329b27b8aed6
https://github.com/metno/noresm-dev/commit/bbec72fa49ed57ab70d5052b8b4c0162eeb6ab88

SourceMods are available on FRAM/NIRD:
<span style="font-family:monospace;font-size:125%">/projects/fram/nn2345k/ingo/CMIP6/Forcing/Volc/SourceMods_noresm_cesm1.2</span>
<span style="font-family:monospace;font-size:125%">/projects/fram/nn2345k/ingo/CMIP6/Forcing/Volc/SourceMods_noresm_cesm2beta6</span>

The folder <span style="font-family:monospace;font-size:125%">SourceMods_noresm_cesm2beta6</span> also contains a modified version of CAM's <span style="font-family:monospace;font-size:125%">build-namelist</span> script that needs to be installed in <span style="font-family:monospace;font-size:125%">components/cam/bld/</span>.

Configuration of user namelists

For certain compsets the below specifications are applied as automatically. Still, there is no harm in putting the same settings in your <span style="font-family:monospace;font-size:125%"> user_nl_cam </span> in your case directory.

CESM1.2 - climatological background forcing

Specify following in your <span style="font-family:monospace;font-size:125%"> user_nl_cam </span> to activate the use of CMIP6 compliant volcanic background forcing:

! Users should add all user specific namelist changes below in the form of
! namelist_var = new_namelist_value
prescribed_volcaero_datapath = '/cluster/shared/noresm/inputdata/atm/cam/volc'
prescribed_volcaero_file = 'CMIP_CAM6_radiation_average_v3_reformatted.nc'
prescribed_volcaero_cycle_yr = 1850
prescribed_volcaero_type = 'CYCLICAL'
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'
fincl1 = 'AODVVOLC', 'ABSVVOLC'

Note that <span style="font-family:monospace;font-size:125%"> rad_climate </span> is specified because CAM's <span style="font-family:monospace;font-size:125%">build-namelist</span> script will otherwise add an extra entry that was needed by the CMIP5 volcanic forcing implementation.

CESM1.2 - transient forcing

Specify following in your <span style="font-family:monospace;font-size:125%"> user_nl_cam </span> to activate the use of CMIP6 compliant transient (1850-2014) volcanic forcing:

! Users should add all user specific namelist changes below in the form of
! namelist_var = new_namelist_value
prescribed_volcaero_datapath = '/cluster/shared/noresm/inputdata/atm/cam/volc'
prescribed_volcaero_file = 'CMIP_CAM6_radiation_v3_reformatted.nc'
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'
fincl1 = 'AODVVOLC', 'ABSVVOLC'

CESM2_beta

The only difference to the CESM1.2 setting is that following extra specification needs to be specified in the case's <span style="font-family:monospace;font-size:125%"> user_nl_cam</span>:

prescribed_strataero_file = ' '

This will deactivate the use of NCAR's alternative CMIP6 volcanic forcing. CAM's original <span style="font-family:monospace;font-size:125%">build-namelist</span> script does not properly recognise the deactivation and will issue an error that both <span style="font-family:monospace;font-size:125%">prescribed_strataero_file</span> and <span style="font-family:monospace;font-size:125%">prescribed_volcaero_file</span> are set.

As a workaround, replace <span style="font-family:monospace;font-size:125%">components/cam/bld/build-namelist</span> in your model tree with the modified version <span style="font-family:monospace;font-size:125%">/nird/projects/fram/nn2345k/ingo/CMIP6/Forcing/Volc/SourceMods_noresm_cesm2beta6/build-namelist </span>