Remove aerosol completly..

[cam_iitd10@gmail_com]

Hi Eaton,

i want run CAM4.0 with aerosol effect completely removed. i have only mixed ideas about how to do.
so please suggest me the required change. so that my confusions get resolved.
Thank you in advance.

Ram
IIT Delhi India

 

[eaton]

Aerosols affect the cam4 physics via the direct radiative effect (no indirect effects). All constituents that interact with the radiation are set in the rad_climate namelist variable. By default for cam4 that variable is set as follows (by build-namelist):

rad_climate = 'P_Q:H2O', 'D_O2:O2', 'D_CO2:CO2', 'D_ozone:O3', 'D_N2O:N2O', 'D_CH4:CH4', 'D_CFC11:CFC11',
'D_CFC12:CFC12', 'D_sulf:/fs/cgd/csm/inputdata/atm/cam/physprops/sulfate_camrt_c080918.nc',
'D_dust1:/fs/cgd/csm/inputdata/atm/cam/physprops/dust1_camrt_c080918.nc',
'D_dust2:/fs/cgd/csm/inputdata/atm/cam/physprops/dust2_camrt_c080918.nc',
'D_dust3:/fs/cgd/csm/inputdata/atm/cam/physprops/dust3_camrt_c080918.nc',
'D_dust4:/fs/cgd/csm/inputdata/atm/cam/physprops/dust4_camrt_c080918.nc',
'D_bcar1:/fs/cgd/csm/inputdata/atm/cam/physprops/bcpho_camrt_c080918.nc',
'D_bcar2:/fs/cgd/csm/inputdata/atm/cam/physprops/bcphi_camrt_c080918.nc',
'D_ocar1:/fs/cgd/csm/inputdata/atm/cam/physprops/ocpho_camrt_c080918.nc',
'D_ocar2:/fs/cgd/csm/inputdata/atm/cam/physprops/ocphi_camrt_c080918.nc',
'D_SSLTA:/fs/cgd/csm/inputdata/atm/cam/physprops/ssam_camrt_c080918.nc',
'D_SSLTC:/fs/cgd/csm/inputdata/atm/cam/physprops/sscm_camrt_c080918.nc'

This list contains all the active gas and aerosol species. The way to remove the effect of aerosols is to remove them from this list. So you need to specify to build-namelist the value of rad_climate that you want rather than allowing it to set the default value. Removing all the aerosol species results in the following setting for rad_climate:

rad_climate = 'P_Q:H2O', 'D_O2:O2', 'D_CO2:CO2', 'D_ozone:O3', 'D_N2O:N2O', 'D_CH4:CH4', 'D_CFC11:CFC11',
'D_CFC12:CFC12'

The way you identify the aerosol constituents in the rad_climate list, other than by knowing the specific names, is that an aerosol specie is always contained in a string that contains the name of a file (this file contains physical and optical properties of the aerosol). The gas phase constituents are the strings where the field after the final semi-colon is the name of the gas specie as it is know to the radiation code.

There is one other way that the aerosols can affect the climate and that is through the deposition of dust and carbon species that affect the albedos in the surface components. In the CAM4 code when running with prescribed aerosols (which is the default) the aerosol depositions are read from datasets by both the CLM and CICE components. So to completely turn off aerosol effects you'll need to turn off reading those datasets as well. This is probably a small effect so perhaps you can ignore it. But if not then consult user guides of those components to figure out how to turn of the reading of those datasets.

 

[jechu@pusan_ac_kr]

Dear Eaton,

I also want to remove the aerosol forcing in CAM4 simulation and estimate the direct radiative forcing by aerosol.
In the previous version (CAM3), it was possible to use 'radforce' so that aerosol radiative forcing could be calcuated by 'QRS-QRS_RF'.
However, I couldn't find the 'radforce' option in CAM4.
Is that changed to another name? or just removed?

Your reply to this thread seems like run with active calculation (not a passive calculation).
Please let me know to get the pure radiative forcing of aerosol (not include aerosol feedback effect).

Thank you.
jechu

 

[eaton]

The "radforce" diagnostic calculations that were in cam3 were removed
during the development of cam4/cam5 because the original calculations
contained many unstated assumptions (for example they were only implemented
in the shortwave part of the code) and we decided to move the
implementation of these calculations to the rrtmg code where they could be
done correctly.

We have an alternative approach that may meet your needs.
While CAM removed the diagnostics for CAMRT instantaneous
forcing, the PORT tool may be useful. It is released as
part of CESM. (PORT = parallel offline radiative transfer)

PORT has some documentation
https://wiki.ucar.edu/pages/recentlyupdated.action?key=port

and in the paper:
http://www.geosci-model-dev-discuss.net/5/2687/2012/gmdd-5-2687-2012.pdf

This tool has been used for several published works.

 

[brianpm]

I see that the rad_climate namelist variable is also present in CAM5. It shows up as something like: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/cesm/cseg//inputdata//atm/cam/physprops/mam3_mode1_rrtmg_c110318.nc',         'M:mam3_mode2:/glade/p/cesm/cseg//inputdata//atm/cam/physprops/mam3_mode2_rrtmg_c110318.nc', 'M:mam3_mode3:/glade/p/cesm/cseg//inputdata//atm/cam/physprops/mam3_mode3_rrtmg_c110318.nc'Just for clarification, does the explanation above also go for CAM5? That is, can the direct effects of aerosol be turned off just by removing the *mam3* parts of the rad_climate variable? 

 

[CESM researcher]

I see that the rad_climate namelist variable is also present in CAM5. It shows up as something like: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/cesm/cseg//inputdata//atm/cam/physprops/mam3_mode1_rrtmg_c110318.nc', 'M:mam3_mode2:/glade/p/cesm/cseg//inputdata//atm/cam/physprops/mam3_mode2_rrtmg_c110318.nc', 'M:mam3_mode3:/glade/p/cesm/cseg//inputdata//atm/cam/physprops/mam3_mode3_rrtmg_c110318.nc'Just for clarification, does the explanation above also go for CAM5? That is, can the direct effects of aerosol be turned off just by removing the *mam3* parts of the rad_climate variable?

Has this problem been resolved? I also encountered similar confusion, can you give me some advice.Thank you in advance

 

[hannay]

Chapter 5. Physics modifications via the namelist

Example 5.2. Aerosol radiative forcing
To compute the total aerosol radiative forcing we need a diagnostic calculation in which all the aerosols have been removed. To do this we start from the default setting for the rad_climate variable, use that as the initial setting for rad_diag_1, and then edit that initial setting to remove the aerosols. In the cam5 physics this involves removing the specification of the three modes, so we end up with a setting in our build-namelist command that looks like this
$camcfg/build-namelist ... \
-namelist "&cam ...
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' /"

 

[kamingfung@link_cuhk_edu_hk]

Hi,

I tried to specify the variable in `user_nl_cam`:

rad_climate = 'A:Q:H2O', 'N:O2:O2',
'A:CO2:CO2', 'A:O3:O3',
'A:N2O:N2O', 'A:CH4:CH4',
'N:CFC11STAR:CFC11', 'A:CFC12:CFC12'

to remove the aerosol climate effect, but received the following error:

ERROR: init_modes ERROR: cannot find physics buffer field num_c1

Would you please advise how it shall be resolved? Thank you.

I am running CESM 2.1.1 with CAM6-chem using TS1 chemistry.

 

[eaton]

There is an assumption in the code that if prognostic aerosols are present, then they will affect the climate. One way to remove the effect of aerosols on the climate would be to modify the code in radiation_tend subroutine (in src/physics/rrtmg/radiation.F90). There are calls to aer_rad_props_sw and aer_rad_props_lw. Just zero out the output variables after those calls, i.e., aer_tau, aer_tau_w, aer_tau_w_g, aer_tau_w_f, aer_lw_abs.

If you are interested in aerosol radiative forcing then the effects of aerosols can be removed in a diagnostic calculation by using the namelist variable rad_diag_1 instead of rad_climate.

 

[CESM researcher]

Chapter 5. Physics modifications via the namelist

Example 5.2. Aerosol radiative forcing
To compute the total aerosol radiative forcing we need a diagnostic calculation in which all the aerosols have been removed. To do this we start from the default setting for the rad_climate variable, use that as the initial setting for rad_diag_1, and then edit that initial setting to remove the aerosols. In the cam5 physics this involves removing the specification of the three modes, so we end up with a setting in our build-namelist command that looks like this
$camcfg/build-namelist ... \
-namelist "&cam ...
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' /"

Thank you very much for eaton reply and prompt, I have another question；Where is the build-namelist command. Forgive my clumsiness，I still can't find where this is? How to set“$camcfg/build-namelist ... \-namelist "&cam ...”. Thank you in advance

 

[eaton]

When using CESM scripts you don't directly modify the build-namelist command. Instead you just put the rad_diag_1 specification into the user_nl_cam file. That file is processed by the scripts to provide input to the build-namelist command.

 

[jialiu]

When I set just change the radiation. Will other variables change？
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' /"

 

[hannay]

This is do a second radiation that ignore the aerosols. This will not change the model answers.
To output variables related to the second radiation you need to add them as fincl with a "_d1"
For instance,
fincl1 = 'FSNT_d1', 'FSNTC_d1', 'FSNS_d1', 'FSNSC_d1'

 

[jialiu]

This is do a second radiation that ignore the aerosols. This will not change the model answers.
To output variables related to the second radiation you need to add them as fincl with a "_d1"
For instance,
fincl1 = 'FSNT_d1', 'FSNTC_d1', 'FSNS_d1', 'FSNSC_d1'

So it can't get feedback on temperature and precipitation？

 

[CESM researcher]

Chapter 5. Physics modifications via the namelist

Example 5.2. Aerosol radiative forcing
To compute the total aerosol radiative forcing we need a diagnostic calculation in which all the aerosols have been removed. To do this we start from the default setting for the rad_climate variable, use that as the initial setting for rad_diag_1, and then edit that initial setting to remove the aerosols. In the cam5 physics this involves removing the specification of the three modes, so we end up with a setting in our build-namelist command that looks like this
$camcfg/build-namelist ... \
-namelist "&cam ...
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' /"

Hi hannay
Recently，I want tried different simulations by changing the refractive index of single aerosol species (for Black carbon, organics, and sulfate) one at a time.(cesm1.2.2-cam5).I think "Example 5.2. Aerosol radiative forcing" express removal of aerosol optical properties，so that the only aerosol forcing mechanism is the indirect effect.（Example 5.2. Aerosol radiative forcing http://www.cesm.ucar.edu/models/cesm1.2/cam/docs/ug5_3/ch05.html）
Am I right to think so？It will be of great help, if you could give some guidance to me。How to Set parameters？

 

[ohmpawat]

So it can't get feedback on temperature and precipitation？

I recently encountered the same problem. Have you know how to reveal the aerosols affect the other variable such as precipitation? Thanks in advance!

 

[jialiu]

I recently encountered the same problem. Have you know how to reveal the aerosols affect the other variable such as precipitation? Thanks in advance!

You can try to modify the aerosol inputdata which is "ext_frc_specifier" or "ext_emis_specifier" in atm_in.

 

[ohmpawat]

You can try to modify the aerosol inputdata which is "ext_frc_specifier" or "ext_emis_specifier" in atm_in.

I will try it. Thanks a lot! Besides, I am confused about the file that there is bc file in "ex_frc_specifier" and mod_refs. What is the function about these bc file. "ex_frc_specifier" files aren't taken part in calculating radiation? It would be appreciated for any reply! Thanks a lot!

 

[jialiu]

I will try it. Thanks a lot! Besides, I am confused about the file that there is bc file in "ex_frc_specifier" and mod_refs. What is the function about these bc file. "ex_frc_specifier" files aren't taken part in calculating radiation? It would be appreciated for any reply! Thanks a lot!

I guess it's black carbon.

 

[jialiu]

I will try it. Thanks a lot! Besides, I am confused about the file that there is bc file in "ex_frc_specifier" and mod_refs. What is the function about these bc file. "ex_frc_specifier" files aren't taken part in calculating radiation? It would be appreciated for any reply! Thanks a lot!

This part of the emissions files are in calculating radiation.