Climatology Workflows¶

The package supports remapping and extrapolating several observational temperature/salinity climatologies (provided privately by Shenjie Zhou on 30-Sep-2025). These are currently preliminary and not yet published; the metadata and provenance will be expanded once a public release occurs.

Supported Climatologies¶

Each climatology is selected with a clim_name passed to the remap or extrapolation CLI/ API. Internally, a configuration file under i7aof/clim/*.cfg supplies variable/dimension names and the relative input path (under the ISMIP base input directory) for that climatology.

clim_name	Description (brief)	Source file (relative)
`zhou_annual_30_sep`	Annual mean over full observational period (exact years TBD)	`Updated_TS_Climatology/OI_Climatology.nc`
`zhou_summer_30_sep`	Summer-only (austral summer months) mean over full period	`Updated_TS_Climatology/OI_summer_Climatology.nc`
`zhou_2000_annual_30_sep`	Annual mean restricted to observations from 2000 onward	`Updated_TS_Climatology/OI_2000_Climatology.nc`

Variables provided: conservative temperature ct and absolute salinity sa (with optional *_mse uncertainty fields if present in future updates). The raw vertical coordinate is pressure (dbar) and is converted to a monotonically increasing height coordinate (meters, positive up) during preprocessing.

Remapping¶

Remapping performs two stages:

Vertical pipeline: mask invalid cells, interpolate to the ISMIP z_extrap levels, and vertically renormalize using a valid fraction mask.
Horizontal remap to the ISMIP projected grid (bilinear, conservative, or nearest-stod per [remap] method).

Command-line example:

ismip7-antarctic-remap-clim \
	--clim_name zhou_annual_30_sep \
	--config my-config.cfg

Output path pattern:

<workdir>/remap/climatology/<clim_name>/<original>_ismip<res>.nc

Extrapolation¶

Climatology extrapolation adds a dummy singleton time dimension (size

so the legacy Fortran extrapolation executables (which assume a time axis) can be reused. This dimension is removed again in the finalized output.

ismip7-antarctic-extrap-clim \
	--clim_name zhou_annual_30_sep \
	--config my-config.cfg

Outputs (one per variable):

<workdir>/extrap/climatology/<clim_name>/<remapped_stem>_<var>_extrap.nc

Post-extrap vertical resampling¶

After extrapolation, a conservative resampling step maps z_extrap to z levels (from 20 m to 60 m by default). The workflow uses the same Zarr-first approach as CMIP (single write without time appends) and converts to a final NetCDF alongside the Extrap output. Dimension order is (z, y, x) for climatologies (no time).

Dimension Ordering¶

Climatology remap outputs enforce variable dimension order (z_extrap, y, x) prior to extrapolation. During extrapolation a dummy time is inserted as the most slowly varying dimension resulting in (time, z_extrap, y, x)—mirroring CMIP workflow inputs so the Fortran code reads the data consistently.

Configuration Keys¶

Each i7aof/clim/zhou_*.cfg file defines:

[climatology]
lat_var, lon_var, lat_dim, lon_dim
lev_var, lev_dim (pressure) -> converted to lev (meters)
filename (relative path under input base dir)
ct_var, sa_var (variable names)

User overrides (e.g. input base directory) can be supplied through a user config passed with --config or via the Python API.

Planned Enhancements¶

Publish provenance and observational period ranges.
Support inclusion of mean-square-error or uncertainty variables when provided.
Add validation utilities for vertical coordinate consistency.

Python API¶

Programmatic usage mirrors the CMIP workflows:

from i7aof.remap.clim import remap_climatology
from i7aof.extrap.clim import extrap_climatology

remap_climatology('zhou_annual_30_sep', user_config_filename='my.cfg')
extrap_climatology('zhou_annual_30_sep', user_config_filename='my.cfg')

Refer also to Workflows for integrating climatology products in a full CMIP+climatology processing chain.