The ziso test group (compass.ocean.tests.ziso.Ziso) implements variants of the Zonally Idealized Southern Ocean (ZISO) test case (see ziso in the User’s Guide) at 2.5, 5, 10 and 20-km resolutions. Here, we describe the shared framework for this test group and the 4 types of test cases currently supported: default, long, particles, and with_frazil.


The shared config options for the ziso test group are described in ziso in the User’s Guide.

Additionally, the test group has several shared namelist and streams files, some for shared parameters and streams for forward runs (namelist.forward and streams.forward), some specific to the resolution of the run and with an eye toward including more resolutions in the future (namelist.<res>.forward and streams.<res>.forward), and some related to enabling analysis members in a run and outputting their results (namelist.analysis and streams.analysis).


The class compass.ocean.tests.ziso.initial_state.InitialState defines a step for setting up the initial state for each test case.

First, a mesh appropriate for the resolution is generated using mpas_tools.planar_hex.make_planar_hex_mesh(). Then, the mesh is culled to remove periodicity in the y direction. A vertical grid is generated, with 100 non-uniform layers according to the 100layerE3SMv1 distribution, but squashed so the bottom of the deepest layer is at 2500 m depth. Finally, the initial temperature field is computed along with uniform salinity and zero initial velocity. The temperature profile is significantly different for test cases with frazil-ice production compared to those without.


The class compass.ocean.tests.ziso.forward.Forward defines a step for running MPAS-Ocean from the initial condition produced in the initial_state step. Namelist and streams files are generated when the test case is set up (combining the *.forward and *.analysis files from the test group) and updated at runtime based on the config options in the [ziso] section of the config file.

A dictionary res_params is used to set parameters like the number of cores and the time steps for each resolution:

res_params = {'20km': {'cores': 20,
                       'min_cores': 2,
                       'cores_with_particles': 32,
                       'min_cores_with_particles': 12,
                       'dt': "'00:12:00'",
                       'btr_dt': "'00:00:36'",
                       'mom_del4': "5.0e10",
                       'run_duration': "'0000_00:36:00'"},
              '10km': {'cores': 80,
                       'min_cores': 8,
                       'cores_with_particles': 130,
                       'min_cores_with_particles': 50,
                       'dt': "'00:06:00'",
                       'btr_dt': "'00:00:18'",
                       'mom_del4': "6.25e9",
                       'run_duration': "'0000_00:18:00'"},
              '5km': {'cores': 300,
                      'min_cores': 30,
                      'cores_with_particles': 500,
                      'min_cores_with_particles': 200,
                      'dt': "'00:03:00'",
                      'btr_dt': "'00:00:09'",
                      'mom_del4': "7.8e8",
                      'run_duration': "'0000_00:09:00'"},
              '2.5km': {'cores': 1200,
                        'min_cores': 120,
                        'cores_with_particles': 2100,
                        'min_cores_with_particles': 900,
                        'dt': "'00:01:30'",
                        'btr_dt': "'00:00:04'",
                        'mom_del4': "9.8e7",
                        'run_duration': "'0000_00:04:30'"}}

If Particles are includes (in the particles test cases), we first generate the required graph partition, then partition the particles, and finally run MPAS-Ocean (including updating PIO namelist options):

if self.with_particles:
    cores = self.cores
    partition(cores, self.config, self.logger)
    run_model(self, partition_graph=False)


The compass.ocean.tests.ziso.ZisoTestCase class defines most of the ZISO test cases. If a baseline is provided when calling compass setup, the test case ensures that the final values of temperature and layerThickness are identical to the baseline values. If particles are included, a number of particle-related variables and timers are also validated against the baseline.


The compass.ocean.tests.ziso.with_frazil.WithFrazil includes default config options:

# namelist options for Zonally periodic Idealized Southern Ocean (ZISO)
# testcases

# Initial temperature profile constant
initial_temp_t1 = 0.0

# Initial temperature profile tanh coefficient
initial_temp_t2 = -1.0

# Initial temperature profile tanh length scale
initial_temp_h1 = 300.0

# Initial temperature profile linear coefficient
initial_temp_mt = 0.0

This test performs a 90-second (3-time-step) run on 4 cores, including frazil-ice formation but without analysis. If a baseline is provided when calling compass setup, the test case ensures that the final values of temperature and layerThickness as well as a number of frazil-related variables are identical to the baseline values.