cosine_bell

In most cases, the polaris.tasks.ocean.cosine_bell.CosineBell task performs a series of runs that advect a bell-shaped tracer blob around the sphere. The mesh resolution and time step are varied according to the refinement type (space, time, or both). Advected results are compared with a known exact solution to determine the rate of convergence.

There is also a restart test, described below, that performs only two time steps of the test to verify the exact restart capability.

framework

The config options for the cosine_bell tasks are described in cosine bell in the User’s Guide.

Additionally, the test uses a forward.yaml file with a few common model config options related to drag and default horizontal and vertical momentum and tracer diffusion, as well as defining mesh, input, restart, and output streams. This file has Jinja templating that is used to update model config options based on Polaris config options, see Convergence Tests.

base_mesh

Cosine bell tasks use shared base_mesh steps for creating Quasi-uniform and Icosahedral Spherical Meshes at a sequence of resolutions.

init

The class polaris.tasks.ocean.cosine_bell.init.Init defines a step for setting up the initial state at each resolution with a tracer distributed in a cosine-bell shape.

forward

The class polaris.tasks.ocean.cosine_bell.forward.Forward descends from polaris.ocean.convergence.spherical.SphericalConvergenceForward, and defines a step for running MPAS-Ocean from an initial condition produced in an init step. The time step is determined from the resolution based on the dt_per_km config option in the [convergence_forward] section. Other model config options are taken from forward.yaml.

analysis

The class polaris.tasks.ocean.cosine_bell.analysis.Analysis descends from polaris.ocean.convergence.analysis.ConvergenceAnalysis, and defines a step for computing the error norm (L2) for the results at each resolution, saving them in convergence_tracer1.csv and plotting them in convergence_tracer1.png.

validate

The class polaris.tasks.ocean.cosine_bell.validate.Validate is a step for validating the results between two cosine-bell runs. It is currently used to verify bit-for-bit restart in the restart test described below.

viz

The visualization step is available only in the cosine_bell/with_viz tasks. It is not included in the cosine_bell in order to keep regression as fast as possible when visualization isn’t needed.

The class polaris.tasks.ocean.cosine_bell.viz.Viz is a step for plotting the initial and final states of the advection test for each resolution. The colormap is controlled by these options:

# options for visualization for the cosine bell convergence test case
[cosine_bell_viz]

# colormap options
# colormap
colormap_name = viridis

# the type of norm used in the colormap
norm_type = linear

# A dictionary with keywords for the norm
norm_args = {'vmin': 0., 'vmax': 1.}

See global lat/lon plots for more details.

Task structure and shared steps

The CosineBell task is constructed to support multiple refinement types (space, time, or both) and optionally includes visualization steps. It uses shared steps for the base mesh, initial condition, and forward runs across different tasks and resolutions. The steps are organized as follows:

For each refinement factor (resolution/time step), a shared base mesh step is created.
An initial condition step is created for each mesh.
A forward step is created for each mesh and time step.
If visualization is enabled, a viz step is created for each mesh/time step.
An analysis step is created to compare results across all refinement factors.

Symlinks are created within the task’s work directory to make shared steps discoverable and to avoid redundant computation.

decomp

The class polaris.tasks.ocean.cosine_bell.decomp.Decomp defines a decomposition test across core counts. It runs the Cosine Bell test at coarse resolution once each on 12 and 24 cores to verify bit-for-bit reproducibility for tracer advection across different core counts.

restart

The polaris.tasks.ocean.cosine_bell.restart.Restart class defines a restart check that performs two time steps of the Cosine Bell test at coarse resolution, then performs the second time step again as a restart run to verify the bit-for-bit restart capability for tracer advection.

restart_step

The polaris.tasks.ocean.cosine_bell.restart.RestartStep class defines both steps of the restart run, the “full” run (2 time steps) and the “restart” run (repeating the last time step after a restart).