which one should I use? CAM-chem or WACCM?

[11438023@zju_edu_cn]

Dear all, I am planning to run some cases to simulate the stratospheric aerosol injection (for example, injecting SO2 into the stratospheric) using CESM 1.2.2.  However, I am a little confused whether I should use CAM5-chem or WACCM? I saw a number of studies used WACCM to do similar simulations. But I also notice some works used CAM5-chem to study the aerosol emission problem...  Can anyone point me out what's the difference between using these two configurations? and where could I find the corresponding description...?  Best

 

[tilmes]

Non of the listed models are suited to study stratospheric SO2 injections. The best model that has been released to the community to study SO2 injections is CESM2 using WACCM. Recent studies that are documented in the literature were performed with a non-released intermediate version of WACCM. For more information on the model version used, please see this paper;Mills M. J. , J. H. Richter, S. Tilmes, B. Kravitz, D. MacMartin, S. Glanville, A. Schmidt, J. J. Tribbia, A. Gettelman, C. Hannay, J. T. Bacmeister, D. E. Kinnison, F. Vitt, and J.-F. Lamarque, 2017: Radiative and chemical response to interactive stratospheric aerosols in fully coupled CESM1(WACCM), JGR-Atmospheres
[https://doi.org/10.1002/2017JD027006]CAM5 and CAM4-chem were also used for stratospheric aerosol geoengineering studies, but in these cases SO2 was not injected but the aerosol layer was presribed.Simone 

 

[11438023@zju_edu_cn]

Hi Simone,Thanks for your general responses. We decided to use the prescribed aerosol distribution data provided by G4SSA.So in this case,(1) which CAM type do you suggest (just want to make sure I choose the right one)?:CAM5 with "-chem none", default CAM5 (user guide says that the default CAM5 uses trop-mam3 scheme while CAM_CONFIG_OPTS is "-phys cam5"  right?), or CAM5-chem with both trop and strat chemistry? or even CAM4-CAM if it's relatively computationally cheaper?One thing I found is, only when I use "-chem none" I see the choice of "prescribed_aero_nl" in atm_in... Does that mean I should stick with CAM5 with "-chem none" ? Also, I noticed that Xia et al. (2016,2017) used CAM4-chem with both tropospheric and stratospheric chemistry. I am a little confused how combined prescribed sulfate aerosol amount and active stratospheric chemistry works... (2) is that possible to vary the prescribed sulfate aerosol forcing for like twenty years with all other settings under the slice year-1850 simulation?  Thanks. Best,Lei 

 

[11438023@zju_edu_cn]

I am going to use CAM4, but still not sure whether I should turn on the chemistry part "-chem trop_strat_soa" and vary the aerosol with time...

 

[tilmes]

Hi,I have used the file for a simulation that was based on the LENS release tag: http://www.cesm.ucar.edu/projects/community-projects/LENS/This is a 1degx1deg  CAM5 version. However, the file had to be manipulated for me to apply this for this version of the model, since it requires the mass mixing ratio of SO4 in a specific format.If you want to run that case, the attached file woudl work this way (it is defined for the year 2040-2079), for example:&prescribed_volcaero_nl
 prescribed_volcaero_datapath           = ....
 prescribed_volcaero_file               = 'geomip_ccmi_2020-2071_volc_v3_h2so4_mass_flipped_new_strat.nc'
 prescribed_volcaero_cycle_yr          = 2042
 prescribed_volcaero_type               = 'CYCLICAL'
 prescribed_volcaero_fixed_ymd          = 0
/you may also have to modify the radiation: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:mam3_mode1:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam3_mode1_rrtmg_c110318.nc',
  'M:mam3_mode2:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam3_mode2_rrtmg_c110318.nc',
  'M:mam3_mode3:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam3_mode3_rrtmg_c110318.nc',
  'N:VOLC_MMR:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/rrtmg_Bi_sigma1.8_c100521.nc'
  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',
   'M:mam3_mode1:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam3_mode1_rrtmg_c110318.nc',
   'M:mam3_mode2:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam3_mode2_rrtmg_c110318.nc',
   'M:mam3_mode3:/glade/p/cesmdata/cseg/inputdata/atm/cam/physprops/mam3_mode3_rrtmg_c110318.nc'

Simone

 

[tilmes]

To answer the earlier question, you can also use CESM1.2.2. and use CAM4, and you don't need to turn on the chemistry, if you are only interested in the climate effects. For that case, you don't need to modify the aerosol input file, Cheers, Simone