realistic_global

The realistic_global task group contains tasks that use realistic global ocean meshes, bathymetry and forcing. It currently contains two kinds of tasks:

woa23, a mesh-independent preprocessing task that builds a reusable World Ocean Atlas 2023 (WOA23) hydrography product on the native 0.25-degree latitude-longitude grid.
analysis_members, short forward runs on realistic global meshes that exercise the global-statistics analysis member and compare its output between MPAS-Ocean and Omega.

supported models

The woa23 task is model-independent and does not require either MPAS-Ocean or Omega to be built.

The analysis_members tasks support both MPAS-Ocean and Omega.

woa23

This task is the Polaris port of the legacy Compass utility/extrap_woa workflow. It combines January and annual WOA23 climatologies, uses a cached e3sm/init combined-topography product on the WOA grid to define the ocean mask used during preprocessing, and then fills missing temperature and salinity values through staged horizontal and vertical extrapolation.

The task can be set up with:

polaris setup -t ocean/spherical/realistic_global/hydrography/woa23 ...

description

The task is organized into inspectable steps:

combine_topo from the e3sm/init component is used to combine topography GEBCO and Bedmap3 datasets on the WOA23 0.25-degree latitude-longitude grid.
combine creates woa_combined.nc by combining January and annual WOA23 in-situ temperature and practical-salinity fields, then deriving conservative temperature and absolute salinity.
extrapolate creates the final woa23_decav_0.25_jan_extrap.nc product.
viz produces horizontal maps and vertical sections of the extrapolated product. This step is not run by default.

This layout is intended to match Polaris shared-step conventions so the WOA23 preprocessing pipeline can later be reused by mesh-dependent realistic_global initialization tasks.

mesh

N/A. This task operates on the native WOA23 latitude-longitude grid rather than an MPAS mesh.

vertical grid

N/A. The task preserves the standard WOA23 depth levels.

initial conditions

The source fields come from the WOA23 January and annual climatologies in the Polaris input database.

forcing

N/A.

time step and run duration

N/A.

config options

# Options related to generating a reusable WOA23 hydrography product
[woa23]

# the minimum weight sum needed to mark a new cell valid in horizontal
# extrapolation
extrap_threshold = 0.01

# target depths for horizontal plots of the extrapolated product (m)
horizontal_plot_depths = 0.0, 200.0, 400.0, 600.0, 800.0

# maximum depth to include in section plots (m)
section_max_depth = 2000.0

# endpoints of a transect through Filchner Trough and into the Filchner
# ice-shelf cavity
filchner_start_lon = -46.0
filchner_start_lat = -71.5
filchner_end_lon = -38.5
filchner_end_lat = -81.2

# endpoints of a transect through the Ross Ice Shelf cavity
ross_start_lon = 176.0
ross_start_lat = -72.0
ross_end_lon = -171.0
ross_end_lat = -84.0

The viz step is further controlled by the [woa23_viz_temperature], [woa23_viz_salinity], [woa23_viz_section_temperature] and [woa23_viz_section_salinity] sections, each of which supports the standard Polaris colormap options described in global lat/lon plots.

cores

The local combine and extrapolate steps run serially. The combine_topo step is intended to use the cached e3sm/init output because regenerating the combined topography product is substantially more expensive.

analysis_members

These tasks perform a short forward run on a realistic global mesh with the global-statistics analysis member enabled, then plot time series of the resulting statistics. Their main purpose is to compare the analysis-member output of MPAS-Ocean and Omega on the same mesh and initial condition.

A task is defined for each of two meshes:

mesh	cells	time step	run duration
`QU.240km`	7,153	10 min	10 days
`EC30to60E2r2`	236,853	45 s	1 day

They can be set up with, e.g.:

polaris setup -t ocean/spherical/realistic_global/QU.240km/analysis_members_test ...

description

Each task contains three steps:

forward runs the ocean model from a cached initial condition, writing both a regular output.nc history file and the global statistics produced by the analysis member.
global_stats plots time series of the minimum, maximum, mean and standard deviation of each state variable, both as absolute values and as anomalies relative to the initial value. This step is not run by default.
viz plots global maps of the state variables at the beginning and end of the run, along with the zonal and meridional wind stress. This step is not run by default.

The global_stats step accounts for a difference between the two models: Omega writes the standard deviation directly, whereas MPAS-Ocean writes the root-mean-square, from which the standard deviation is computed.

WARNING: As of Omega commit 061d0ab, Omega does not area- or volume-weight the global stats while MPAS-Ocean does. Thus, the two models’ stats cannot be directly compared.

mesh

The meshes are standard E3SM global ocean meshes downloaded from the Polaris input database rather than generated by the task: the quasi-uniform 240-km QU.240km mesh and the eddy-closure EC30to60E2r2 mesh, which varies from 30 km to 60 km.

vertical grid

The vertical grid is the one supplied with the cached initial condition for each mesh, so there are no vertical-grid config options for these tasks.

initial conditions

The initial condition is a cached, model-specific file from the realistic_global section of the Polaris input database. For Omega, a TEOS-10 initial condition is used and the same file supplies the mesh, vertical coordinate and initial state. For MPAS-Ocean, a zerovel (zero initial velocity) file supplies the mesh and initial state.

forcing

Zonal and meridional wind stress are read from the initial-condition file and applied through bulk wind stress. Vertical mixing uses CVMix with convection and shear mixing enabled, and a constant implicit bottom drag coefficient of 1.0e-3 is applied.

time step and run duration

The time step and run duration are set per mesh as shown in the table above. Output, including the global statistics, is written once per day.

config options

[ocean]

# Equation of state type
eos_type = teos-10

[realistic_global]

# Time step duration per kilometer [s]
dt_per_km = 3.0

The viz step is controlled by the [realistic_global_viz_temperature], [realistic_global_viz_salinity], [realistic_global_viz_layerThickness], [realistic_global_viz_windStress] and [realistic_global_viz_kineticEnergyCell] sections, each of which supports the standard Polaris colormap options described in global lat/lon plots.

cores

The number of cores used by the forward step is determined algorithmically from the number of cells in the mesh. The global_stats and viz steps run serially.