barotropic channel

This test group is unified by being a singly-periodic domain with barotropic dynamics. It is primarily designed to test lateral boundary conditions and can be configured to be very computationally lightweight. A visualization step is included with the primary purpose of inspecting the relative vorticity field at boundary vertices to verify correct implementation of free slip boundary conditions, which would not be a source of vorticity. The test group may also be useful in testing algorithms at the limit of 3 cells between boundaries such as occurs in narrow passages in the global ocean.

suppported models

These tasks support both MPAS-Ocean and Omega.

mesh

The mesh is planar with periodicity in the x direction and no-flow boundary condition in the y direction. The default horizontal resolution is 10km, set by cfg option barotropic_channel:resolution and the default dimensions are 100km by 30km, set by cfg options barotropic_channel:lx and barotropic_channel:ly.

vertical grid

The test case is currently hard coded to have a bottom depth equal to 2/3 times the cfg option vertical_grid:bottom_depth for all cells along the non- periodic boundary and vertical_grid:bottom_depth for all other cells.

The default coordinate type given by cfg option vertical_grid:coord_type is z-level so that layers terminate against the non-periodic boundary to test how terms handle this condition.

# Options related to the vertical grid
[vertical_grid]

# the type of vertical grid
grid_type = uniform

# Number of vertical levels
vert_levels = 3

# Depth of the bottom of the ocean
bottom_depth = 100.0

# The type of vertical coordinate (e.g. z-level, z-star)
coord_type = z-level

# Whether to use "partial" or "full", or "None" to not alter the topography
partial_cell_type = None

# The minimum fraction of a layer for partial cells
min_pc_fraction = 0.1

initial conditions

The velocity field is spatially uniform and set according to cfg options barotropic_channel:zonal_velocity and barotropic_channel:meridional_velocity.

Temperature and salinity are spatially uniform and hard-coded to 1 degC and 35 PSU. These fields do not play a role in the dynamics.

forcing

This test case is forced by a spatially-uniform wind field of magnitude determined by cfg options barotropic_channel:zonal_wind_stress and barotropic_channel:meridional_wind_stress.

time step and run duration

The time step for forward integration is 1 minute and the duration is 10 days.

config options

[barotropic_channel]

# the size of the domain in km in the x and y directions
ly = 30.0
lx = 100.0

zonal_velocity = 0.0
meridional_velocity = 0.0

zonal_wind_stress = 0.1
meridional_wind_stress = 0.0

resolution = 10.

horizontal_viscosity = 1.e-2

bottom_drag = 1.e2

cores

The number of cores is determined by goal_cells_per_core and max_cells_per_core in the ocean section of the config file.

default

description

The default test case runs the init, forward, and viz steps and uses the same config options as the test group.