Skip to content

c3s-seasonal.md

Latest commit

 

History

History
148 lines (114 loc) · 13 KB

c3s-seasonal.md

File metadata and controls

148 lines (114 loc) · 13 KB
Raw

C3S Seasonal Multi-System

What this model is

The C3S seasonal forecast service is a multi-system seasonal prediction service operated by the Copernicus Climate Change Service, implemented by ECMWF on behalf of the EU. It collects real-time forecasts and hindcasts from nine independently operated, fully coupled seasonal prediction systems, regrids them to a common 1° grid, and publishes them through the Copernicus Climate Data Store (CDS) as raw ensemble fields, monthly statistics, and bias-adjusted (anomaly) products. Forecasts extend roughly 6–7 months ahead. It succeeded EUROSIP, which was retired in October 2019.

Note that this is an operational seasonal prediction service, not a climate-projection product, despite the "Climate Change Service" branding — see Notes on scope.

Who runs it

  • Organization: Copernicus Climate Change Service (C3S), implemented by ECMWF on behalf of the European Union. Data archived in ECMWF's MARS and served via the CDS.
  • Country / region: European Union (multi-national, with non-European in-kind contributors)
  • Coordinating body / programme: C3S / Copernicus. Contributing centres: ECMWF, UK Met Office, Météo-France, DWD, CMCC, NCEP, JMA, ECCC, and BoM.

What area it covers

  • Coverage: Global
  • Domain details: All systems delivered on a common 1° × 1° regular lat-lon grid, with grid points centred at half-degree latitude/longitude (180 latitude values, −89.5 to 89.5). Native model resolutions are considerably finer and vary by system (see Coupled configuration).

Basic details

  • Model type: Multi-system ensemble (umbrella) of fully coupled seasonal prediction systems — raw ensemble fields, monthly statistics, and bias-adjusted probabilistic products
  • Model system / core: Varies by member (see Multi-model composition)
  • Range class: Seasonal
  • Forecast length: ~6–7 months, varying by system (CMCC 184 days; ECCC 214; ECMWF, UKMO, NCEP and JMA 215; BoM 217; DWD 6 calendar months; Météo-France 7 calendar months)
  • Initialization cadence: Monthly nominal start dates. Several systems initialize in lagged mode (daily or across the preceding month) but are encoded to a common nominal start date — see Notes.
  • Ensemble generation: Mixed — burst ensembles (ECMWF, DWD, CMCC), lagged/daily-initialized ensembles (UKMO, NCEP, JMA, BoM), and dual-component lagged systems (ECCC, Météo-France)
  • Ensemble size: No single fixed total; per-system real-time sizes are ECMWF 51; UKMO 2 members/day (most recent 50 used for C3S products); Météo-France 25 members each from two lagged starts plus 1; DWD 50; CMCC 50; NCEP 4 members/day (52 used); JMA 5 members/day (55 used); ECCC 10 members each from two starts, per component system; BoM 11 members each. The CDS serves the complete member set even where C3S products use a subset.
  • Temporal output resolution: Sub-daily (6-hourly) and daily raw fields; monthly aggregates
  • Output aggregation levels: Original time resolution; monthly statistics; bias-adjusted/post-processed products (anomalies)

Coupled configuration

Each member is an independently developed, fully coupled system. There is no common formulation — only the common 1° delivered grid. Native configurations (status April 2026):

Centre System Atmosphere Ocean
ECMWF SEAS5 TCO319/L91 (~36 km), 91 levels to 0.01 hPa 0.25° ORCA, 75 levels
UK Met Office GloSea6-GC5.1 N216/L85 (~60 km mid-lat), 85 levels to 85 km 0.25° ORCA, 75 levels
Météo-France System 9 TL359/L137 (0.5°), 137 levels to 0.01 hPa 0.25° ORCA, 75 levels
DWD GCFS2.2 T127 (~100 km), 95 levels to 0.01 hPa 0.4° TP04, 40 levels
CMCC SPS4 (CMCC-CM3) ~0.5° lat-lon, 83 levels to 0.01 hPa 0.25° ORCA, 75 levels
NCEP CFSv2 T126/L64 (~1°), 64 levels to 0.02 hPa 0.25°–0.5°, 40 levels
JMA CPS4 TL319 (~55 km), 128 levels to 0.01 hPa 0.25° tripolar, 60 levels
ECCC CanESM5.1p1bc T63 (~2.8°), 49 levels to 1 hPa 1° ORCA, 45 levels
ECCC GEM5.2-NEMO ~1.1° (~110 km), 85 levels to 0.1 hPa 1° ORCA, 50 levels
BoM ACCESS-S2 N216 (~60 km mid-lat), 85 levels to 85 km 0.25° ORCA, 75 levels

Initialization

Initialization varies by member: each centre initializes its own system from its own operational analyses and/or reanalyses. There is no shared C3S initialization. Per-system detail is documented in the individual C3S contribution pages linked from the Knowledge Base.

Hindcasts (reforecasts)

Hindcasts are essential to this dataset — the bias-adjusted products depend on them, and the CDS system keyword must match between a real-time forecast and its hindcast.

  • Hindcast periods (vary by system): ECMWF 1981–2016; UK Met Office 1993–2016; Météo-France 1993–2018; DWD 1993–2023; CMCC 1993–2022; NCEP 1993–2016; JMA 1993–2020; ECCC 1980–2023 (no hindcast data available for start dates before 1993); BoM 1993–2018.
  • Hindcast ensemble sizes: ECMWF 25; UKMO 7 members per start (1st, 9th, 17th, 25th); Météo-France 15 each plus 1; DWD 30; CMCC 30; NCEP 4 per start date (every 5 days); JMA 5 per start (2 lagged start dates); ECCC 10 each per component; BoM 3 each.
  • Production schedule: Most systems produce hindcasts as a fixed dataset. The UK Met Office produces them on-the-fly, generated close to the matching real-time forecast — which is why its system values increment annually (600–605, then 610 for GloSea6-GC5.1 from April 2026).
  • Distributed alongside forecasts? Yes — via the same CDS datasets, selected by product type.

Sources of predictability

ENSO is the dominant seasonal driver, with coupled ocean heat content, sea ice, land-surface memory, and stratospheric state contributing. The multi-system design is intended to sample model uncertainty better than any single system.

Multi-model composition

  • Contributing centres and current systems (from April 2026), with the CDS system keyword: ECMWF SEAS5 (51); Météo-France System 9 (9); UK Met Office GloSea6-GC5.1 (610); DWD GCFS2.2 (22); CMCC SPS4 (4); NCEP CFSv2 (2); JMA CPS4 (4); ECCC CanESM5.1p1bc (4) and GEM5.2-NEMO (5); BoM ACCESS-S2 (2).
  • Combination method: Multi-system combination products are published alongside the individual system forecasts; all members are regridded to the common 1° grid.
  • Common delivered grid: 1° × 1°.
  • ECCC structure: ECCC's contribution is CanSIPSv3.0, supplied as two independent forecasting systems (CanESM5.1p1bc and GEM5.2-NEMO) rather than as a single combined system — the same split seen in NMME.
  • Per-contributor terms: Contributions from NCEP, JMA, ECCC, and BoM are in-kind from non-European centres and are covered by an additional licence condition (see Data availability).
  • Historical / retired systems: ECMWF System 4; Météo-France Systems 5–8; Met Office GloSea5-GC2 and GC2-LI and earlier GloSea6 issues; DWD GCFS2.0/2.1; CMCC SPS3/SPS3.5; JMA CPS2/CPS3; ECCC CanCM4i, GEM-NEMO, GEM5-NEMO.

What it provides

CDS catalogue entries are organized by variable type (single-level vs. pressure-level) and by level of post-processing (original time resolution, monthly aggregation, bias-adjusted), plus a separate ocean dataset. Confirmed entries include:

  • seasonal-original-single-levels — daily and sub-daily (6-hourly) single-level fields
  • seasonal-monthly-single-levels — monthly statistics on single levels
  • seasonal-monthly-ocean — monthly ocean variables (available from March 2023; archived in netCDF)
  • Corresponding pressure-level and post-processed (anomaly) entries

(Flag: the full CDS dataset list could not be enumerated directly — the catalogue requires authentication — so treat the live CDS catalogue as authoritative for exact dataset identifiers.)

Viewer-only siblings (out of scope): the graphical seasonal forecast products on the C3S website.

Data availability

  • Is the data free? Yes — free of charge, but access requires a free ECMWF/CDS account and per-dataset licence acceptance.
  • License: Copernicus licence, plus an additional licence to use non-European contributions covering the in-kind contributions from NCEP, JMA, ECCC, and BoM. C3S states that all data published in the CDS as part of the seasonal forecast multi-system may be used and redistributed without restrictions; citation and acknowledgement requirements are given on the CDS alongside the licence.
  • Is the data downloadable? Yes
  • Data formats: GRIB (native; all data held in ECMWF's MARS archive in GRIB). NetCDF is offered as a conversion but is documented as experimental and not recommended, except for the ocean variables in seasonal-monthly-ocean, which are archived in netCDF.
  • Official download location:
  • Access route notes: No anonymous bulk directory or FTP mirror exists — retrieval is exclusively via the CDS web forms or the CDS API. Terms and conditions must be accepted per dataset before download. Retrievals require the system keyword; matching a real-time forecast to the correct hindcast system value is essential for computing anomalies correctly.

Release schedule

  • ECMWF: 6th of each month at 12 UTC
  • All other forecast systems: 10th of each month at 12 UTC

Notes

  • Scope note — registration gate. Access requires a free account and per-dataset licence acceptance. This is self-service registration, not an approval gate, and the licence permits unrestricted redistribution. This requires confirming that self-registration is treated as in-scope, and revisiting the COPERNICUS.md exclusion wording, which currently excludes "Copernicus Climate… services" — language aimed at reanalysis/CAMS but which as written would collide with this forecast product.
  • Nominal start dates vs. real initialization. Several systems (Météo-France, ECCC) initialize members in lagged mode but encode them in the CDS as if all were initialized on the 1st of the month. UKMO, NCEP, JMA, and BoM build a nominal month from members initialized across the preceding month. The real initialization times are not always exposed.
  • system keyword is load-bearing. It identifies the forecasting system version and differs in meaning between fixed-hindcast systems (mapped to the centre's version numbering) and on-the-fly-hindcast systems (UK Met Office, three-digit incrementing scheme).
  • ECMWF SEAS5 system=5 is deprecated. From November 2022 only system=51 real-time data is served; system=5 hindcasts should not be used alongside it (different 1° interpolation and grid definition).
  • Member overlap. NCEP CFSv2 has its own entry; ECCC's contribution is CanSIPS, also with its own entry. This entry cross-references rather than re-documenting.
  • Succeeded EUROSIP, retired October 2019. IMME/EuroSIP as displayed elsewhere is a separate, non-open activity (a Systems Not in the Catalog candidate).
  • Relationship to ECMWF SEAS5 standalone. SEAS5 is openly licensed as part of ECMWF's real-time catalogue, but the practical open route for its seasonal data is this CDS channel rather than the free data.ecmwf.int Open Data subset.

Recent version history

  • April 2026: Met Office GloSea6-GC5.1 (system=610) replaces GloSea6 (605).
  • January/February 2026: JMA CPS4 (system=4) introduced.
  • August 2025: CMCC SPS4 (system=4) replaces SPS3.5.
  • May 2025: BoM joins with ACCESS-S2; Météo-France System 9 replaces System 8.
  • April 2025: DWD GCFS2.2 (system=22) replaces GCFS2.1.
  • August 2024: ECCC upgrades to CanSIPSv3.0 components (system=4 and 5).
  • March 2023: Ocean variables dataset added.
  • November 2022: ECMWF SEAS5 re-versioned as system=51.
  • October 2019: EUROSIP retired; C3S multi-system takes over.
  • September 2017: First real-time forecasts (ECMWF, Météo-France, UK Met Office).

Official documentation