====== 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.