realistic_global

The realistic_global task group contains tasks that use realistic global ocean meshes, bathymetry and forcing. It currently contains five 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.
jra55, a mesh-independent preprocessing task that builds a reusable wind-stress product on the native JRA55-do TL319 grid.
init, which creates mesh-specific ocean initial conditions from that hydrography and forcing together with the culled mesh from e3sm/init.
analysis_members, forward runs on realistic global meshes that exercise the analysis members: short runs comparing the global statistics of MPAS-Ocean and Omega, and one-year Omega runs writing what the analysis tasks read.
restart, a short run split across a restart, checking that the history output survives the restart intact.

supported models

The woa23 and jra55 tasks are model-independent and do not require either MPAS-Ocean or Omega to be built.

The init task and the short analysis_members tasks support both MPAS-Ocean and Omega. The 1_year tasks support only Omega, since the analysis reads only Omega output.

The restart task supports Omega only. It is a regression test for the way Omega writes its history time axis across a restart, and MPAS-Ocean stamps its output with xtime rather than an elapsed time measured from the start of the clock, so the failure it looks for cannot arise there.

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.

jra55

This task builds a time-invariant global wind-stress product from JRA55-do 10-m winds. Its purpose is narrow: standalone runs need a realistic, constant-in-time momentum input so that dynamic adjustment can spin down fast waves against a physically sensible circulation. It is not intended as a climate forcing product, and it does not include surface restoring, thermal or freshwater fluxes, or any time variation.

polaris setup -t ocean/spherical/realistic_global/forcing/jra55 ...

The source is JRA55-do v1.5.0 (MRI-JRA55-do-1-5-0), variables uas and vas: 10-m winds on the TL319 Gaussian grid, 3-hourly, distributed as input4MIPs on ESGF. E3SM forces ocean-only (G-case) runs with JRA55, so the adjusted state is adjusted against something close to what a coupled run will apply. The default time window is January 1958, the first month of the record and of an interannually forced G-case.

Warning

Running the stress step downloads about 3.5 GiB of raw reanalysis into the initial_condition_database. The derived product is in the Polaris cache database, so this happens only when you run this task to regenerate it, and users of the init task get the few-MB product from the Polaris server instead.

The stress is computed at every 3-hourly step and then time-averaged, rather than computing the stress of the time-mean wind. Averaging the wind first discards the gust contribution and underestimates the stress in the storm tracks, which is why the 3-hourly data is needed at all. The bulk formula is the Large and Yeager (2004, 2009) neutral 10-m drag law; the stability correction, the ocean-current-relative wind and any sea-ice drag distinction are deliberately omitted as second-order for this purpose.

description

The task contains two steps:

stress downloads the raw winds and writes jra55_stress.nc on the native TL319 grid. It is cached by default, but this task always runs it.
viz plots global maps of the stress components and magnitude, plus a zonal-mean taux curve. It runs by default in this task, but is left out when the wind-stress steps are pulled into other workflows as shared dependencies, so the plots are not regenerated for every mesh.

The zonal-mean curve is the diagnostic worth looking at. For the default January window it peaks near +0.12 N m^-2 around 50S in the Southern Ocean westerlies, with a trade-wind minimum near -0.06 N m^-2. Do not compare those against published annual-mean stress climatologies, which are considerably stronger in the Southern Ocean – the Compass NCEP 1958-2000 annual mean peaks at +0.19 N m^-2 – because the Southern Ocean westerlies are weaker in austral summer. Compare like with like, or expect a January product to look weak.

mesh

N/A. This task operates on the native JRA55-do TL319 grid rather than an MPAS mesh.

vertical grid

N/A.

initial conditions

N/A.

forcing

N/A. This task produces wind stress for the init task rather than applying any forcing itself.

time step and run duration

N/A.

config options

# Options related to generating a reusable JRA55-do wind-stress product
[jra55]

# the input4MIPs source and version of the JRA55-do dataset
source_id = MRI-JRA55-do-1-5-0
version = v20200916

# the ESGF data node and root path used to download the raw winds.  The
# retired esgf-node.llnl.gov and esgf-node.ornl.gov paths no longer work.
base_url = https://esgf.ceda.ac.uk/thredds/fileServer/esg_cmip6/input4MIPs/CMIP6/OMIP/MRI

# the year and month to average.  January 1958 is the first month of the
# JRA55-do record and of an interannually forced E3SM G-case.
year = 1958
month = 1

# air density used in the bulk formula (kg m^-3)
rho_air = 1.22

# wind speeds below this value (m s^-1) are clamped before evaluating the
# drag law, whose 2.70/U term would otherwise diverge
min_wind_speed = 0.5

# number of time slices to process at once when averaging the stress
time_chunk_size = 24

The viz step is further controlled by the [jra55_viz_taux], [jra55_viz_tauy] and [jra55_viz_tau_mag] sections, each of which supports the standard Polaris colormap options described in global lat/lon plots.

cores

Both steps run serially.

init

The init task creates a mesh-specific ocean initial condition (and, for Omega, a vertical-coordinate file) from the WOA23 hydrography and the culled mesh from e3sm/init, together with a surface forcing file from the JRA55-do wind stress. There is one task for each base and unified mesh:

polaris setup -t ocean/spherical/realistic_global/<mesh_name>/init/task ...

The target model, MPAS-Ocean or Omega, is set by the [ocean] model config option, which polaris setup takes from --model or detects from the build given with -p.

description

The task runs the e3sm/init steps that build and cull the mesh and remap its topography (see Topography Tasks), the steps of the woa23 and jra55 tasks, which read their products from the cache, and then these steps of its own:

cull_topo moves the remapped topography from the base mesh onto the culled ocean mesh.
woa23_map and remap_woa23 remap the WOA23 conservative temperature and absolute salinity to the culled mesh.
jra55_map and remap_jra55 remap the JRA55-do wind stress to the culled mesh. The step fails if the mapping leaves any cell uncovered.
pstar_init builds the p-star vertical coordinate together with the temperature and salinity on it, since each depends on the other through the equation of state. It also fits the bathymetry to the depths the vertical grid can represent and fills isolated bathymetry holes.
initial_state writes mesh.nc, init.nc and, for Omega, vert_coord.nc.
forcing writes forcing.nc with the wind stress on the mesh.
viz writes sanity-check plots and ParaView exports for the initial condition and vertical coordinate: an initial_state_summary.png figure of histograms, a vertical_coordinate.png structure figure, global maps of temperature and salinity at several depths (plus surface and seafloor) and of topography and column diagnostics, vertical transects across the major ocean basins, and xdmf/ subdirectories for ParaView. For Omega, native surface/bottom pressure maps and a TEOS-10 in-situ density (stratification) check are also produced. Global maps of the on-mesh wind stress components and magnitude are also written, which is where remapping artifacts would show up.

On large meshes, viz is the most expensive step: it took 78 minutes of a run of about 2.5 hours on u-oi6to18-lr6to10. It runs only in this task; other workflows that reuse the init steps leave it out.

mesh

Any of the base meshes (Base Mesh Tasks) or unified meshes (Unified base-mesh tasks), culled to the ocean and sea-ice domain by e3sm/init.

vertical grid

The default is the 80-layer E3SMv1 reference grid with the p-star coordinate (see p-star) and partial bottom cells. The 240 km meshes use a cheaper 16-level grid instead (see per-mesh config options).

# Options related to the vertical grid
[vertical_grid]

# the type of vertical grid
grid_type = 80layerE3SMv1

# the type of vertical coordinate
coord_type = p-star

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

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

# Minimum number of vertical levels a valid column must contain (3 is the
# practical minimum for baroclinic dynamics).  Also sets the minimum depth
# clamp together with min_bottom_depth.
min_vert_levels = 3

# Minimum geometric water-column depth (m); cells shallower than this (or than
# the depth needed for min_vert_levels layers) are clamped to it.
min_bottom_depth = 10.0

Columns deeper than the reference grid can represent are made shallower to fit it.

initial conditions

Temperature and salinity come from the extrapolated WOA23 January climatology built by the woa23 task. They are conservative temperature and absolute salinity for Omega, and potential temperature and practical salinity for MPAS-Ocean. The ocean starts at rest, with the sea surface at zero height. Ice-shelf cavities are not supported.

forcing

forcing.nc holds constant-in-time wind stress from the jra55 task: SfcStressZonal and SfcStressMeridional for Omega, windStressZonal and windStressMeridional for MPAS-Ocean. Both models take zonal and meridional components at cell centers and project onto edges themselves. Surface restoring and the thermal and freshwater fluxes are future work, as are the forward-model settings that apply the forcing.

time step and run duration

N/A. This task does not run the ocean model.

config options

[realistic_global_init]
# Approximate number of MPAS cells to target per MPI task when building
# the WOA23 and JRA55-do remapping weights with mbtempest / ESMF.  Building
# weights is a purely horizontal, geometric problem with no vertical
# structure, so these counts are much larger than the ~200 cells per core
# used to size forward runs.
remap_cells_per_task = 10000

# Rough maximum cells per task, used to compute the minimum task count
# (min_tasks).  This is a rule of thumb, not a hard limit: the task count is
# rounded to the nearest whole number, so a task may get somewhat more cells.
remap_min_cells_per_task = 50000


# Options related the ocean component
[ocean]

# Equation of state type, defaults to mpas-ocean default
eos_type = teos-10


# Options related to the Coriolis force
[coriolis]

# Coriolis type for a realistic global (Earth-rotation) mesh, giving
# f = 2 * omega * sin(latitude)
type = spherical


# Options for the realistic global init visualization step
[realistic_global_init_viz]

# Projection for the global maps, must be supported by polaris.viz
projection = Robinson

# Longitude of the center of the global maps
central_longitude = 200.

# Depths (m below the surface) at which to plot global temperature/salinity
# maps.  One vertical level is selected per depth; its actual depth may vary.
depths = 0, 100, 500, 1000, 2000, 4000

# the type of norm used in the colormaps (set per-variable at run time)
norm_type = linear

# additional arguments to provide to the colormap norm (set at run time)
norm_args = {}


# Vertical transects to plot, crossing relevant ocean basins.  Each named
# transect is a list of an even number (>= 4) of values giving alternating
# lon, lat waypoints in degrees (a straight line uses two waypoints; a zonal
# circumnavigation needs intermediate waypoints).
[realistic_global_init_viz_transects]

# comma-separated list of transects to plot (each defined as an option below)
transects = atlantic_meridional, pacific_meridional, indian_meridional,
    southern_ocean_zonal

# Atlantic meridional section near 30 W
atlantic_meridional = -30.0, -60.0, -30.0, 65.0

# Pacific meridional section near 150 W
pacific_meridional = -150.0, -60.0, -150.0, 60.0

# Indian meridional section near 80 E
indian_meridional = 80.0, -60.0, 80.0, 25.0

# Southern Ocean zonal section near 60 S (waypoints around the globe)
southern_ocean_zonal = -180.0, -60.0, -90.0, -60.0, 0.0, -60.0, 90.0, -60.0,
    180.0, -60.0

The mapping steps use the map_tool option in the [mapping] section, moab by default. The colormap and its limits for each viz plot are set at run time from the variable and the range of its data, so the [realistic_global_init_viz] colormap options are not meant to be edited.

per-mesh config options

Some config options need to differ from one mesh to the next. These live in one optional file per mesh, <mesh_name>.cfg, under polaris/tasks/ocean/realistic_global/mesh_configs. When a realistic_global task is set up, the options for its mesh are added after the task’s own config file, so they override the defaults. Most meshes have no file there at all and simply use the defaults; you can still override any option for a single mesh in your own user config file.

These are separate from the per-mesh files in polaris/mesh/spherical/unified. The two are joined by the mesh name but have different owners: the mesh component describes the mesh itself (resolutions, river networks, sizing fields, total cell count), while the ocean component describes what the ocean does on that mesh. An option specific to the ocean belongs in mesh_configs, not in the mesh component.

Currently:

qu240km, icos240km and u-oi240-lr240 replace the default 80-layer vertical grid with a cheap 16-level tanh_dz grid with a 3000 m bottom depth. The shallow ocean is deliberate: these coarse meshes exist for fast smoke-testing of E3SM, Omega and MPAS-Ocean rather than for physically realistic simulations.
All four unified meshes set culled_ocean_cell_count, the approximate size of the ocean + sea-ice culled mesh that the ocean model actually runs. It is used to size MPI task counts and is smaller than the full mesh, which includes land and river-channel refinement that is culled away first.

For example, u-oi240-lr240.cfg contains:

# Ocean-specific properties of this mesh
[realistic_global_mesh]

# Approximate cell count of the ocean + sea-ice culled mesh that the ocean
# model actually runs, used to size ocean MPI task counts (ntasks/min_tasks).
culled_ocean_cell_count = 7500


# Options related to the vertical grid
[vertical_grid]

# the type of vertical grid
grid_type = tanh_dz

# Number of vertical levels
vert_levels = 16

# Depth of the bottom of the ocean
bottom_depth = 3000.0

# The minimum layer thickness
min_layer_thickness = 3.0

# The maximum layer thickness
max_layer_thickness = 500.0

Options the per-mesh file does not set (coord_type, min_vert_levels, min_bottom_depth, and so on) are inherited from the task’s config file as usual.

cores

woa23_map and jra55_map run on MPI tasks sized from the mesh’s ocean-culled cell count: one task per remap_cells_per_task cells, and no fewer than one per remap_min_cells_per_task cells. Both are rounded to the nearest whole task, so they are rules of thumb rather than hard limits. The other steps of this task run serially.

analysis_members

These tasks perform a forward run on a realistic global mesh with the global-statistics analysis member enabled, then plot time series of the resulting statistics. There are two runs on each mesh:

short compares the analysis-member output of MPAS-Ocean and Omega on the same mesh and initial condition.
1_year runs Omega for a year with its MonthlyAverages and MOC analysis groups on, writing what the analysis tasks read. It is meant to become a cached step for regression testing the omega_analysis suite.

mesh	cells	time step	barotropic step	`short` run
`QU.240km`	7,153	1 h	3 min	5 days
`EC30to60E2r2`	236,853	30 min	1 min	1 day

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

polaris setup -t ocean/spherical/realistic_global/QU.240km/analysis_members/short ...
polaris setup -t ocean/spherical/realistic_global/QU.240km/analysis_members/1_year ...

The QU.240km short run is in the omega_pr suite. The 1_year runs are in no suite. The QU.240km year takes about 8 minutes on a Chrysalis node, and the EC30to60E2r2 year about 50 minutes on 6 nodes, writing about 40 GB.

description

The short tasks contain 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.

The 1_year tasks contain the forward and global_stats steps. The run writes, in the forward step’s work directory:

monthly_means_1MonthTimeStats.<year>-<month>.nc, the monthly means from the MonthlyAverages group of conservative temperature, absolute salinity, pseudo-thickness, specific volume, the layer-midpoint and interface elevations, sea surface height, normal velocity and kinetic energy;
moc_1MonthTimeStats.<year>-<month>.nc, the monthly-mean global overturning streamfunction from the MOC group, in 60 latitude bins on QU.240km and Omega’s default of 180 on EC30to60E2r2;
global_stats_1DayInstants, daily global statistics of the state, kinetic energy and sea surface height;
output/ocn.hist.<year>-<month>.nc, a monthly snapshot of the same fields as the monthly means, taken at the instant each mean is finalized, as a check on the means.

Omega names a time-mean file for the instant it was finalized, the start of the following month, so the twelve files covering year 1 are named 0001-02 through 0002-01. The analysis accounts for this; see analysis.

To analyze the run, point the omega_analysis suite at the omega.yml in the forward step’s work directory:

[ocean_analysis]

omega_config_filename = <work_dir>/ocean/spherical/realistic_global/<mesh>/analysis_members/1_year/forward/omega.yml

[ocean_analysis_climatology]

start_year = 1
end_year = 1

[ocean_analysis_time_series]

start_year = 1
end_year = 1

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.

The harmonic and biharmonic momentum viscosities are set per mesh by the mom_del2 and mom_del4 config options, raised from Omega’s defaults of 1.0e3 m^2/s and 1.2e11 m^4/s to reduce, but not remove, grid-scale noise in the velocity. On QU.240km, the biharmonic viscosity is raised to 1.0e15 m^4/s. On EC30to60E2r2, the harmonic viscosity is raised to 1.0e4 m^2/s, since Omega does not scale the biharmonic viscosity with cell width and it cannot be raised enough to damp the 60-km cells without going unstable in the 30-km ones. These values are provisional until Omega has KPP and the fix to its pressure-gradient errors over bathymetry. These are coarse runs for testing the analysis members, not scientifically valid simulations.

time step and run duration

The time steps and the length of the short run are set per mesh by the dt, btr_dt and short_run_duration config options, as shown in the table above. On QU.240km they are E3SM’s values for this mesh. The forward run uses the split-explicit time stepper (SplitExplicitRK2 in Omega). The short run writes output, including the global statistics, once per day.

The 1_year run lasts 365 days from 0001-01-01, one year on the No Leap calendar. Restarts are written monthly, because Omega requires the restart interval to be a multiple of every averaging period.

config options

[ocean]

# Equation of state type
eos_type = teos-10

[realistic_global]

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

# options for the analysis_members tasks
[analysis_members]

# The fields to plot global statistics for, using MPAS-Ocean (Polaris
# standard) names.  Leave this empty, as it is by default, to plot every
# field the run wrote statistics for, which is what the models' own default
# lists give.  A field the run did not write is skipped with a message, not
# an error.
fields =

# The baroclinic and barotropic time steps: E3SM's MPAS-Ocean values for
# oQU240.  A 2-hour step gave a growing surface hotspot along the Aleutians in
# a one-year run.
dt = 01:00:00
btr_dt = 00:03:00

# The length of the short run.  The 1_year run is always 365 days.
short_run_duration = 0005_00:00:00

# The number of latitude bins of the 1_year run's MOC: three degrees, since
# Omega's default of one degree is finer than the mesh
moc_num_bins = 60

# The harmonic momentum viscosity (m^2/s): Omega's default
mom_del2 = 1.0e3

# The biharmonic momentum viscosity (m^4/s).  Omega's default of 1.2e11 is
# meant for much finer meshes and leaves grid-scale noise in the velocity on
# this one.  1.0e15 gave the least of the values tried in one-year runs;
# 3.0e15 is unstable with a 1-hour time step.  Some noise remains in the
# wind-driven top layer.
mom_del4 = 1.0e15

The time steps, run length, MOC bins and viscosities are for QU.240km. On EC30to60E2r2, dt is 30 minutes, btr_dt 1 minute, short_run_duration 1 day, moc_num_bins 180, mom_del2 1.0e4 and mom_del4 1.2e11.

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.

restart

This task checks that splitting a run across a restart leaves the history output alone. It is a regression test for Omega #482, where a run continued from a restart silently overwrote the history frames written before the restart instead of appending to them, leaving a file that was well formed and simply missing the earlier half of the run.

It can be set up with:

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

description

The task contains four steps:

full_run covers the whole four-hour period in one go.
first_segment covers the first two hours and writes a restart.
second_segment continues from that restart and covers the last two hours, appending its history frames to the ones first_segment left behind.
validate compares the history of the restart chain with the history of the full run.

Each segment writes its restart into a directory of its own under the task’s restarts directory, and a continuing segment reads its predecessor’s. second_segment starts from a copy of first_segment’s output.nc, so that it finds on disk what a continuation run would find: a history file that already holds the earlier frames and has to be appended to.

validate checks two things, because a restart can go wrong in two ways. The time axis has to hold every frame of the whole period, in increasing order, which is what #482 broke. The state then has to match the uninterrupted run, which is the usual exact-restart check.

mesh

The QU.240km quasi-uniform 240-km mesh, downloaded from the Polaris input database, as for the analysis_members tasks.

vertical grid

The vertical grid is the one supplied with the cached initial condition.

initial conditions

A cached TEOS-10 Omega initial condition from the realistic_global section of the Polaris input database, which supplies the mesh, vertical coordinate and initial state.

forcing

As for the analysis_members tasks: zonal and meridional wind stress from the initial-condition file, applied through bulk wind stress.

time step and run duration

The task uses the split-explicit time stepper (SplitExplicitRK2 in Omega) with a 1-hour baroclinic and a 3-minute barotropic time step, and a biharmonic momentum viscosity of 1.0e15 m^4/s, the settings of the year-long QU240 runs that the ocean analysis is tested on. Each segment runs for two hours and the full run for four, with a history frame every hour, so each segment writes two frames and the whole period has four. The period is short on purpose: the task is about how the model writes its history across a restart, not about the circulation, and it is meant to be cheap enough for the pull-request suite.

config options

[ocean]

# Equation of state type
eos_type = teos-10

[realistic_global]

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

cores

The number of cores used by each forward step is determined algorithmically from the number of cells in the mesh. The validate step runs serially.