CMIP6 volcanic forcing¶
Code and installation¶
The CMIP6 volcanic forcing implementation has been committed to the noresm (CESM1.2) repository and the noresm-dev (CESM2_beta) repository. The changes 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: \
/nird/projects/fram/nn2345k/ingo/CMIP6/Forcing/Volc/SourceMods_noresm_cesm1.2
/nird/projects/fram/nn2345k/ingo/CMIP6/Forcing/Volc/SourceMods_noresm_cesm2beta6
The folder
SourceMods_noresm_cesm2beta6
also contains a modified version of CAM’s
build-namelist
script that needs to be installed in
components/cam/bld/
Configuration of user namelists¶
For some compsets the below specifications are applied automatically. Still, you can specify the same settings in your
user_nl_cam
in your case directory.
CESM1.2 - climatological background forcing¶
Specify following in your
user_nl_cam
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
rad_climate
is specified here because CAM’s
build-namelist
script will otherwise add an extra entry that was needed by the CMIP5 volcanic forcing implementation.
CESM1.2 - transient forcing¶
Specify following in your
user_nl_cam
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 - climatological background & transient¶
The
user_nl_cam
namelist settings are the same as for CESM1.2, except that following extra line needs to be added:
prescribed_strataero_file = ' '
This will deactivate the use of NCAR’s alternative CMIP6 volcanic forcing.
CAM’s original
build-namelist
script does not properly recognise the deactivation and will issue an error that both
prescribed_strataero_file
and
prescribed_volcaero_file
are set.
As a workaround, replace
components/cam/bld/build-namelist
in your model tree with the modified version
- ::
- /nird/projects/fram/nn2345k/ingo/CMIP6/Forcing/Volc/SourceMods_noresm_cesm2beta6/build-namelist
Writing the volcanic forcing to the history output for verification¶
The complete set of optical parameters of the volcanic forcing can be written to CAM-OSLO’s monthly history output by adding following in the case’s
user_nl_cam
fincl1 = 'ext_sun1','ext_sun2','ext_sun3','ext_sun4','ext_sun5','ext_sun6','ext_sun7','ext_sun8','ext_sun9','ext_sun10','ext_sun11','ext_sun12','ext_sun13','ext_sun14','omega_sun1','omega_sun2','omega_sun3','omega_sun4','omega_sun5','omega_sun6','omega_sun7','omega_sun8','omega_sun9','omega_sun10','omega_sun11','omega_sun12','omega_sun13','omega_sun14','g_sun1','g_sun2','g_sun3','g_sun4','g_sun5','g_sun6','g_sun7','g_sun8','g_sun9','g_sun10','g_sun11','g_sun12','g_sun13','g_sun14','ext_earth1','ext_earth2','ext_earth3','ext_earth4','ext_earth5','ext_earth6','ext_earth7','ext_earth8','ext_earth9','ext_earth10','ext_earth11','ext_earth12','ext_earth13','ext_earth14','ext_earth15','ext_earth16','omega_earth1','omega_earth2','omega_earth3','omega_earth4','omega_earth5','omega_earth6','omega_earth7','omega_earth8','omega_earth9','omega_earth10','omega_earth11','omega_earth12','omega_earth13','omega_earth14','omega_earth15','omega_earth16','g_earth1','g_earth2','g_earth3','g_earth4','g_earth5','g_earth6','g_earth7','g_earth8','g_earth9','g_earth10','g_earth11','g_earth12','g_earth13','g_earth14','g_earth15','g_earth16'
Note that each variable corresponds to a single band, that values are masked below the model’s tropopause and that all values are interpolated online from altitude to pressure. The output can be compared to the original input data which is stored in
CMIP_CAM6_radiation_average_v3.nc
and
CMIP_CAM6_radiation_v3.nc
in
/cluster/shared/noresm/inputdata/atm/cam/volc
on FRAM.