COSP2 in CESM2 Guidance

At this time, COSP2 has been implemented with CESM1/CAM6 physics and released to the public. Here we provide answers to some frequently asked questions. COSP2/CESM2 contacts are Jennifer Kay (University of Colorado/CIRES), Dustin Swales (University of Colorado/CIRES) and Brian Medeiros (NCAR).

What is the easiest way to run COSP within CAM and look at COSP diagnostics using the AMWG diagnostics package? The instructions below assume you are running on Cheyenne but steps will be similar on other supercomputers.

1. Get the CESM2 code from github and check out the externals
   git clone https://github.com/ESCOMP/cesm.git cesm2
cd cesm2
./manage_externals/checkout_externals
2. Create the case COSP2_CESM2 and go to your case directory
   cd cime/scripts
./create_newcase --case /glade/u/home/$USER/COSP2_CESM2 --compset B1850 --res f09_g17
cd /glade/u/home/$USER/COSP2_CESM2

3. Configure CAM6 so that you compile with COSP
   ./xmlchange CAM_CONFIG_OPTS="-phys cam6 -co2_cycle -cosp
4. Set up the case
   ./cesm_setup
5. Edit the CAM namelist to set cosp_amwg equal to .true. With this setting in the CAM namelist, you will runs the radar, lidar, modis, misr and isccp simulators, and save the monthly COSP outputs needed for the AMWG diagnostics package in the CAM h0 files. cosp_amwg=.true.

Note that setting cosp_amwg=.true. is the equivalent of setting:
cosp_histfile_num = 1
cosp_lisccp_sim = .true.
cosp_lradar_sim = .true.
cosp_llidar_sim = .true.
cosp_lmisr_sim = .true.
cosp_lmodis_sim = .true.
cosp_nradsteps = 3
cosp_ncolumns = 10

6. Run CAM for at least one year including months needed for DJF averaging
7. Run the latest version of the AMWG diagnostics package

COSP outputs available in CAM:

COSP namelist options in CAM: