global_ocean

The global_ocean tasks in polaris.tasks.ocean.global_ocean are intended for preprocessing and initialization workflows that are upstream of any particular MPAS mesh. The first task category under this framework is hydrography/woa23, which builds a reusable hydrography product from the World Ocean Atlas 2023 on its native 0.25-degree latitude-longitude grid.

framework

The shared config options for the WOA23 hydrography task are described in global_ocean in the User’s Guide.

The implementation is intentionally organized around reusable Polaris steps rather than around the legacy Compass utility/extrap_woa multiprocessing workflow. One notable design choice is that the task reuses the combined topography product from e3sm/init rather than taking a raw topography filename as a task-specific input.

cached topography dependency

The helper polaris.tasks.ocean.global_ocean.hydrography.woa23.get_woa23_topography_step() creates a shared e3sm/init polaris.tasks.e3sm.init.topo.combine.step.CombineStep configured for a 0.25-degree lat-lon target grid. The polaris.tasks.ocean.global_ocean.hydrography.woa23.task.Woa23 task adds this step with a symlink combine_topo and prefers to use a cached version of its outputs when matching entries are available in the e3sm/init cache database.

This keeps the expensive topography blending logic in one place and makes the ocean hydrography preprocessing task consistent with the broader Polaris approach to shared, cacheable preprocessing steps.

hydrography/woa23

The polaris.tasks.ocean.global_ocean.hydrography.woa23.task.Woa23 task is the Polaris port of the WOA preprocessing part of the legacy Compass workflow.

combine

The class polaris.tasks.ocean.global_ocean.hydrography.woa23.combine.CombineStep combines January and annual WOA23 temperature and salinity climatologies into a single dataset. January values are used where they exist, and annual values fill deeper levels where the monthly product is not available.

WOA23 supplies in-situ temperature and practical salinity, so this step uses gsw to derive conservative temperature and absolute salinity for the canonical woa_combined.nc product.

extrapolate

The class polaris.tasks.ocean.global_ocean.hydrography.woa23.extrapolate.ExtrapolateStep uses the cached combined-topography product on the WOA grid together with woa_combined.nc to build a 3D ocean mask and then fill missing WOA values in two stages:

  1. Horizontal then vertical extrapolation within the ocean mask

  2. Horizontal then vertical extrapolation into land and grounded-ice regions

The final output is woa23_decav_0.25_jan_extrap.nc.