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ECMWF — EWDS (CEMS Early Warning Data Store)#

The ECMWF backend reaches more than one Copernicus Data Store instance through the same cdsapi client. Besides the Climate Data Store (CDS), it can retrieve from the CEMS Early Warning Data Store (EWDS) — the home of GloFAS (Global Flood Awareness System), EFAS, and CEMS fire danger. Each is a separate CADS instance at its own URL; the catalog routes a dataset to the right one via an endpoint field (cds by default, ewds for the datasets below).

Credentials — one token, three stores#

EWDS uses the same Copernicus single sign-on as CDS, and the same Personal Access Token authenticates against CDS, ADS, and EWDS — only the URL differs. So if your ~/.cdsapirc already works for CDS, it works for EWDS too; you do not need a second token. You do, however, have to accept each EWDS dataset's licence once, on its dataset page.

  1. Sign in at https://ewds.climate.copernicus.eu/ (your CDS account works).
  2. Open the dataset page — e.g. https://ewds.climate.copernicus.eu/datasets/cems-glofas-forecast — and tick the licence at the bottom of the Download tab. Acceptance is permanent.
  3. Nothing else to configure: the backend reuses your CDS token from ~/.cdsapirc (or CDSAPI_KEY). To point EWDS at a different token or URL, set EWDS_KEY / EWDS_URL.

If no token can be resolved for a non-CDS endpoint, the backend raises AuthenticationError naming the EWDS_KEY env var and the EWDS profile page.

GloFAS river-discharge forecast#

cems-glofas-forecast delivers GloFAS river discharge on its native regular 0.05° WGS84 grid, as NetCDF (variable dis24). The backend snaps the bbox to that 0.05° grid automatically (regular CDS datasets keep their 0.125° ERA5 snap). Request it with temporal_resolution="daily":

from earthlens import EarthLens

lens = EarthLens(
    data_source="ecmwf",
    variables={
        "cems-glofas-forecast": ["river-discharge-in-the-last-24-hours"],
    },
    start="2026-07-01",
    end="2026-07-01",
    temporal_resolution="daily",
    lat_lim=[0.0, 1.0],
    lon_lim=[0.0, 1.0],
    path="data/glofas",
)
lens.download()   # retrieves via the EWDS endpoint; writes one NetCDF

The row ships sensible defaults in its catalog extras — system_version: operational, hydrological_model: lisflood, leadtime_hour: 24, product_type: control_forecast, delivered unarchived as NetCDF. The output lands at <path>/river_discharge_in_the_last_24_hours_cems-glofas-forecast.nc.

Scope and follow-ups#

Only cems-glofas-forecast is curated in this release (verified end to end against live EWDS). The rest of the EWDS universe is reachable with the same token but not yet wired for download:

Dataset Status / blocker
cems-glofas-forecast Shipped — verified live.
cems-glofas-reforecast, cems-glofas-historical Use hyear/hmonth/hday date keys — need a date-key remap.
cems-glofas-seasonal, cems-glofas-seasonal-reforecast Monthly + leadtime_hour shape.
cems-fire-historical-v1, cems-fire-seasonal Need their valid product_type / dataset_type / system_version combos pinned.
efas-* The public EFAS archive (licence-gated); EFAS real-time is partner-gated and out of scope.

See Usage for the general request shape and Catalog & tooling for the catalog layout.