Note, the following instructions are only valid for the 2017 CESM2 release. If you wish to run the dynamical core configuration prior to the CESM2 release, please contact Isla Simpson (firstname.lastname@example.org)
The following describes the Dry Adiabatic Baroclinic Instability (DABI) test case for the CAM dynamical core. This test case is documented in Polvani, Scott and Thomas (2004), MWR, 132, 2539--2552. It aims to produce a converged solution of the dry, adiabatic, primitive equations by running a short integration (12 days) of a slightly perturbed, baroclinically unstable, midlatitude jet. The initial conditions for this test case consist of a simple zonal flow and a localized temperature perturbation in the mid-latitudes, each of which are specified analytically.
The initial condition files for this test case are provided for the pseudo-spectral dynamical core at three default resolutions within the CESM release (T42L30, T85L30 and T85L60). The T42L30 case is faster to run, but does not produce a result that is quite at the converged solution; this case may be desirable for those who wish to run a quick test to ensure the dynamical core is working well. The other two resolutions take slightly longer to run, but produce the converged solution. These initial condition datasets were generated with NCL codes that can be downloaded here. Users who wish to move on to generate their own initial conditions may find it helpful to use these as a starting point to ensure they have the correct initial condition file format.
Running the DABI test case
After downloading the latest CESM release, users may perform this test by following the procedures outlined below (Note, this configuration is only available from CESM2.0 onward). See the CESM user's guide for more infomation on creating and running new cases. The following describes how to run the DABI test case using a CESM release that is located in the directory $CESM.
Step 1: Create the DABI test case
This can be done using the create_newcase script located in the directory $CESM/cime/scripts/ e.g., for the T42L30 resolution
./create_newcase --compset FDABIP04 --res T42_T42 --case $CASEDIR --mach $MACH
where the case directory ($CASEDIR) and machine ($MACH) are specified by the user. When using yellowstone $MACH = yellowstone, and to run the T85L30 or T85L60 resolutions, replace T42_T42 with T85_T85 or T85z60_T85 respectively.
Step 2: Configure the DABI test case
The DABI compset ensures that most of what is necessary to perform the test case is set up automatically e.g., all dampings, filters, fixers etc have been turned off. The default length of the simulation is set to 5 days, so in order to perform the 12 day test case, the following command must be invoked
./xmlchange --file env_run.xml --id STOP_N --val 12
Step 3: Set up and build the DABI test case
From within $CASEDIR run
Step 4: Run the DABI test case
Step 5: Validate the DABI test case output
A number of fields can be used to check that the simulation has produced the converged solution. Two such fields are shown below for T85L30 (see also Figures 4 and 9 of Polvani, Scott and Thomas (2004)). Figure 1 shows the relative vorticity on the 0.975 sigma level and Figure 2 shows the pressure vertical velocity at sigma=0.5 and 45N, both at midnight of day 12 of the integration. These plots can be reproduced using an ncl script that can be downloaded here. If the dynamical core is set up correctly, these plots should be reproduced to a high degree of accuracy.
Figure 1: Relative vorticty at sigma=0.975, day 12 for the T85L30 DABI integration.
Figure 2: Pressure vertical velocity at sigma=0.5, 45N for day 12 of the DABI integration.