New default namelist for tracer_cnst, prescribed_ozone / prescribed_strataero, and stream_ndep_data

[cecilehannay]

Hi @tilmes and Shawn,

We would like to put the settings and forcing files we are currently using onto the trunk. This includes the latest tracer_cnst, prescribed_ozone / prescribed_strataero, and stream_ndep_data files, as well as several CAM7 namelist settings.

To put the current settings on the trunk, we need answers to all questions below. Thanks a bunch!

Here is the user_nl_cam configuration used in our recent runs:

tracer_cnst_datapath = '/glade/derecho/scratch/shawnh/Forcings_tmp/20260706/b.e30_alpha09b.B1850C_MTt4s.ne30_t233_wgx3.360/atm/proc/TracerCnstFileCyclic1850'
tracer_cnst_file = 'tracer_cnst_MTt4s_halons_3Dmonthly_1850climo360_c20260706.nc'

prescribed_ozone_datapath = '/glade/derecho/scratch/shawnh/Forcings_tmp/20260706/b.e30_alpha09b.B1850C_MTt4s.ne30_t233_wgx3.360/atm/proc/ozone_strataero_day_5_zm'
prescribed_ozone_file = 'ozone_strataero_b.e30_alpha09b.B1850C_MTt4s.ne30_t233_wgx3.360_1850_0005_0030_transient_zm_5day_c20260706.nc'

prescribed_strataero_datapath = '/glade/derecho/scratch/shawnh/Forcings_tmp/20260706/b.e30_alpha09b.B1850C_MTt4s.ne30_t233_wgx3.360/atm/proc/ozone_strataero_day_5_zm'
prescribed_strataero_file = 'ozone_strataero_b.e30_alpha09b.B1850C_MTt4s.ne30_t233_wgx3.360_1850_0005_0030_transient_zm_5day_c20260706.nc'

stream_ndep_data_filename = '/glade/derecho/scratch/shawnh/Forcings_tmp/20260706/b.e30_alpha09b.B1850C_MTt4s.ne30_t233_wgx3.360/atm/proc/NDepositionCyclic1850/fndep_clm_MTt4s_3Dmonthly_1850climo330_c20260706.nc'

To put these on the trunk, we need to:

1. Copy the files into the CESM inputdata repository.
2. Update the namelist defaults and the appropriate use cases.

Modification of use cases

I assume the only use cases that need to be modified are the pre-industrial LTso and MTso use cases:

1850_cam_lt.xml
1850_cam_mt.xml

Could you confirm this is correct?

Where we are planning to put the new input files

tracer_cnst

We were planning to put:

tracer_cnst_MTt4s_halons_3Dmonthly_1850climo360_c20260706.nc

under:

/glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/tracer_cnst

Is this location OK with you, or should we create/use a TracerCnstFileCyclic1850 subdirectory, corresponding to the current directory structure?

Ozone / stratospheric aerosols

We were planning to put:

ozone_strataero_b.e30_alpha09b.B1850C_MTt4s.ne30_t233_wgx3.360_1850_0005_0030_transient_zm_5day_c20260706.nc

under:

/glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/ozone_strataero

Is this location OK with you, or should we create/use an ozone_strataero_day_5_zm subdirectory?

N deposition

For N deposition, we are more puzzled about where the file should go.

The new file is:

fndep_clm_MTt4s_3Dmonthly_1850climo330_c20260706.nc

It looks like these N deposition files have historically been stored under the CLM inputdata directory:

/glade/campaign/cesm/cesmdata/cseg/inputdata/lnd/clm2/ndepdata

Also, since stream_ndep_data_filename is now defined through the CAM namelist, Cheryl was wondering whether the file should instead be placed somewhere under the CAM inputdata directory.

What do you recommend?

Also, should we create/use an NDepositionCyclic1850 subdirectory there?

Thanks,

@cecilehannay , @cacraigucar , and @PeterHjortLauritzen

[tilmes]

A quick comment: these fields are still preliminary and are based on a previous B1850 run with the MTt4s model.
Once we do a new spinup, these files will change of course, just to make sure that is OK

[tilmes]

**I assume the only use cases that need to be modified are the pre-industrial LTso and MTso use cases:

1850_cam_lt.xml
1850_cam_mt.xml
Could you confirm this is correct?**
Correct

**_Here is where we are planning to put the new input files
For tracer_cnst,
we were planning to put
tracer_cnst_MTt4s_halons_3Dmonthly_1850climo360_c20260706.nc
under

/glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/tracer_cnst
Is the location ok with you or should we create/use a TracerCnstFileCyclic1850 subdirectory, corresponding to the current directory structure?_**

For me, it seems to be fine to only have one tracer_cnst directory, where we can store the 1850 files, and the transient files.

**_For ozone/stratospheric aerosols, we were planning to put

ozone_strataero_b.e30_alpha09b.B1850C_MTt4s.ne30_t233_wgx3.360_1850_0005_0030_transient_zm_5day_c20260706.nc
under

/glade/campaign/cesm/cesmdata/cseg/inputdata/atm/cam/ozone_strataero
Is the location ok with you or should we create/use an ozone_strataero_day_5_zm subdirectory?_**

Again, we can just use the ozone_strataero directory and make sure the name reflects what the file is.

**_For N deposition, we are more puzzled where we should put it.

The new file is:

fndep_clm_MTt4s_3Dmonthly_1850climo330_c20260706.nc
it looks like these ndep files have historically been stored under the CLM inputdata directory:

/glade/campaign/cesm/cesmdata/cseg/inputdata/lnd/clm2/ndepdata
Also, since stream_ndep_data_filename is now defined through the CAM namelist, Cheryl was wondering whether the file should instead be placed somewhere under the CAM inputdata directory. What do you recommend?

Also should we create/use an NDepositionCyclic1850 subdirectory there?_**

Again, I am fine to just add it to the traditional directory..

[cecilehannay]

We are trying to get the out-of-the-box configuration closer to the current development runs. That said, I am happy to keep this in user_nl_cam for now if you think this setting is likely to change again soon.