Mask regular data with geometry data - ECMWF internal earthkit training, March 2026

This example masks ERA5 data (regular lat/lon grid) with country boundaries taken from the NUTS inventory.

from earthkit import data as ekd
from earthkit import geo as ekg
from earthkit import plots as ekp
from earthkit import transforms as ekt
from earthkit.transforms._tools import earthkit_remote_test_data_file

remote_era5_file = earthkit_remote_test_data_file("era5_temperature_europe_20150101.grib")
era5_data = ekd.from_source("url", remote_era5_file)

geometry_data = ekg.gisco.nuts_regions(level=0).to_geopandas()
geometry_data.head()

# Mask ERA5 data with geometry
masked = ekt.spatial.mask(
    era5_data, geometry_data, mask_dim="NAME_ENGL", lat_key="latitude", lon_key="longitude"
)
masked

plot_data = masked.isel(forecast_reference_time=0)
figure = ekp.Figure(domain="Europe", rows=2, columns=3)
nmaps = figure.rows * figure.columns

subplot = figure.add_map()
subplot.pcolormesh(era5_data, style="2m-temperature-spectral-celsius")
subplot.title("Original data")

for i in range(nmaps-1):
    subplot = figure.add_map()
    subplot.pcolormesh(plot_data.isel(NAME_ENGL=i), style="2m-temperature-spectral-celsius")
    subplot.title("{NAME_ENGL}")

figure.coastlines()
figure.borders()
figure.legend()
figure.show()