Support of the ICON grid in the Earthkit ecosystem

[ninaburg]

Summary:

ICON forecast data are defined on an unstructured grid. Currently, Earthkit can only access cell indices — not lat/lon coordinates — when loading ICON data. This makes native use of ICON data not supported across most Earthkit components and forces users to regrid to regular grids as a workaround.

Earthkit is now evolving to provide native support for the ICON grid, and this issue is used as a public communication and tracking space to share progress, releases, current capabilities, and upcoming features with the community.

Goal
Enable native ICON grid support in Earthkit:

1. Native unstructured grid loading with lat/lon coordinates using ds = earthkit.data.from_source("file", icon_filename).to_xarray()
2. Direct use in plots using earthkit.plots.quickplot(ds)
3. Diect use in regridding. Methods: linear interpolation and nearest neighbour. Using earthkit.regrid.regrid(ds[0], grid=[1,1])

Status tracking
16.02.2026

✅ Native ICON grid loading with latitude and longitude coordinates is now supported in the released version of earthkit-data
-> https://github.com/ecmwf/earthkit-data/releases/tag/0.19.0

✅ Direct plotting of ICON native grid data is now supported in the released version of earthkit-plots, including earthkit.plots.quickplot(ds) without requiring prior regridding
-> https://github.com/ecmwf/earthkit-plots/releases/tag/0.6.0

⚠️ Native regridding support via earthkit-regrid is not yet fully released. However, it is already functional when using the dedicated develop branch together with the compatible environment.

A fully working example environment and demonstration notebook is available here:
https://github.com/MeteoSwiss/nwp-fdb-polytope-demo/blob/native_grid-16022026/examples/Polytope/work_with_data_native_grid.ipynb

This enables end-to-end workflows including:

• loading ICON native grid data with coordinates
• visualising native grid data directly
• regridding using earthkit-regrid from the development branch

Full official release of earthkit-regrid native ICON support is still in progress.

11.02.2026

The goals outlined above can now be achieved using an experimental dependency setup (pre-release packages and development branches).

Setup instructions and a working example are available in this notebook:
https://github.com/MeteoSwiss/nwp-fdb-polytope-demo/blob/native_grid/examples/Polytope/work_with_data_native_grid.ipynb

⚠️ This is a developer preview and not part of a stable Earthkit release yet.

[ninaburg]

Hi @sandorkertesz, thanks a lot for the notebook you shared with us yesterday. I was able to test it and have added a link in the issue to share the current experimental status.