ESA OC-CCI v6.0¶

ESA Ocean Colour Climate Change Initiative (Ocean_Colour_cci) Version 6.0, 4km resolution data (produced by PML, archived at CEDA, and extended through C3S as "Ocean colour from 1997 to present derived from satellite observations")

Available

At a glance¶

Note on period: The record starts on 1997-09-04 with SeaWiFS. The CEDA v6.0 record ends on 2022-12-31 (status Completed); data from 2023 onward are the C3S CDS and PML extensions. The latest date on the PML server could not be checked because automated reading is blocked. Some days are missing in the SeaWiFS-only period (1997–2000).

Overview¶

The ESA Climate Change Initiative (CCI) Ocean Colour project's multi-sensor merged ocean-colour climate record. Remote-sensing reflectances (Rrs) from SeaWiFS, MERIS, MODIS-Aqua, VIIRS (S-NPP) and OLCI (Sentinel-3A and 3B) are band-shifted to the six MERIS wavelengths, corrected for inter-sensor bias and merged, and chlorophyll-a, Kd(490) and inherent optical properties (IOPs) are then derived. Every value carries per-pixel uncertainty (RMSD and bias), and chlorophyll is a blend of algorithms weighted by optical water class membership. Since v5.0, C3S has produced the data with the same processing chain and keeps extending chlorophyll and reflectance in the C3S CDS.

What changes with the successor¶

OC-CCI v5.0 → OC-CCI v6.0¶

Adds Sentinel-3B OLCI, uses the fourth MERIS reprocessing, and applies OLCI bug fixes, updated system vicarious calibration (SVC) and masking, and QAA v6. MODIS and VIIRS were dropped after 2019, changing the sensor mix in recent years.

Sources: C3S CDS dataset overview (v6.0 changes) · OC-CCI Product User Guide v6.5 (D4.2) · CEDA — v5.0 record (Superseded)

OC-CCI v6.0 → OC-CCI v7.0 Planned¶

The next version, in preparation under CCI+ Phase 2. Plans include an updated in situ database, re-evaluated calibration and new OLCI-era bands (400, 620, 681 and 709 nm). No release date has been announced.

Sources: OC-CCI Product User Guide v6.5 (v7.0 plans) · IOCS 2025 agency talk (NCEO, OC-CCI V7 plans)

Available variables¶

Variable names follow the v6.0 Product User Guide (PUG). Reflectance and IOP wavelengths are the MERIS bands 412, 443, 490, 510, 560 and 665 nm. All are float32 with missing values. The C3S CDS release contains only chlor_a and Rrs (plus observation counts). The PUG uses both MODIS_nobs and MODISA_nobs for the per-sensor count, so check your files.

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Ocean-colour products (L3 composites, 4 km)¶

Per-pixel uncertainty (based on in situ match-ups)¶

Optical water classes and observation counts¶

The full variable list is in the official documentation.

How to get the data¶

• CEDA Archive — OC-CCI v6.0 4 km collection (CDR, 1997-09 to 2022-12) — Direct HTTPS download / OPeNDAP / THREDDS (data.cci.ceda.ac.uk) No login needed
  • No registration needed. Example path esacci/ocean_colour/data/v6.0-release/geographic/netcdf/all_products/monthly/v6.0/2022/ ESACCI-OC-L3S-OC_PRODUCTS-MERGED-1M_MONTHLY_4km_GEO_PML_OCx_QAA-202212-fv6.0.nc. Lighter chlor_a-only files are under netcdf/chlor_a/. Earlier versions (v1 to v5.0) are on the same THREDDS server (https://data.cci.ceda.ac.uk/thredds/catalog/esacci/ocean_colour/data/catalog.html).
• PML oceancolour.org (THREDDS, OPeNDAP, FTP, web GIS) — THREDDS (NetcdfSubset for lat/lon and time subsets, OPeNDAP), FTP, composite browser, web GIS portal
  • The FAQ describes this as the most up-to-date source for the current version (all 4 km variables, plus 1 km chlorophyll and reflectance). NetcdfSubset requests cannot exceed 4 GB, so use Stride to thin them. FTP credentials are published on the ESA data page. Some Mac FTP clients corrupt monthly composites larger than 4 GB, so the team suggests using the terminal.
• C3S Climate Data Store (satellite-ocean-colour) — Web download / CDS API (cdsapi)
  • Requires an ECMWF account and acceptance of the licence. Variables are mass_concentration_of_chlorophyll_a and remote_sensing_reflectance; version is 6_0 (5_0_1 and 5_0 are marked deprecated); projection is regular_latitude_longitude_grid or sinusoidal_grid; temporal_resolution is daily or monthly.
• Copernicus Marine — OCEANCOLOUR_GLO_BGC_L3_MY_009_107 / L4_MY_009_108 (ESA-CCI based) — Copernicus Marine Toolbox / Marine Data Store
  • Chlorophyll, phytoplankton size classes and reflectance (L3 daily, L4 monthly) built from ESA-CCI inputs (datasets such as c3s_obs-oc_glo_bgc-plankton_my_l3-multi-4km_P1D). When checked on 2026-10-13 the catalogue extent ran to 2025-12, with irregular updates. A free Copernicus Marine account is required.
• Google Earth Engine (COPERNICUS/MARINE/SATELLITE_OCEAN_COLOR/V6) — Cloud analysis (chlor_a, Rrs and observation counts from the C3S daily data)
  • When checked on 2026-10-13 it ran through 2026-03-31.

Example code¶

Opens one v6.0 monthly chlorophyll file through the CEDA THREDDS OPeNDAP service (no login) and clips the seas around Korea. For data from 2023 onward, use the C3S CDS (cdsapi) or the PML server.

# pip install xarray netCDF4 numpy
import numpy as np
import xarray as xr

url = ("https://data.cci.ceda.ac.uk/thredds/dodsC/esacci/ocean_colour/data/v6.0-release/"
       "geographic/netcdf/chlor_a/monthly/v6.0/2022/"
       "ESACCI-OC-L3S-CHLOR_A-MERGED-1M_MONTHLY_4km_GEO_PML_OCx-202211-fv6.0.nc")
ds = xr.open_dataset(url)
chl = ds["chlor_a"].sel(lon=slice(120, 132))
chl = chl.where((chl.lat >= 30) & (chl.lat <= 40), drop=True)   # seas around Korea
# Chlorophyll is log-normal: average in log10 space, then transform back
print(float(10 ** np.log10(chl).mean()))

Practical tips¶

• The FAQ warns that uncertainties are generally higher in coastal and turbid waters (such as the coastal Yellow Sea and the southern coast of Korea), where suspended matter or dissolved organic matter rather than chlorophyll may drive the optical properties. Check the uncertainty variables and water class memberships for coastal work.
• Chlorophyll is log-normally distributed. Compute area means, climatologies and trends on log10 values. Statistics from the lat–lon grid over-weight high-latitude cells, so apply area weights or use the sinusoidal files.
• In v6.0, MODIS and VIIRS were dropped from the record after 2019. Coverage and performance in recent years differ from v5.0, and residual inter-sensor bias may remain around sensor transitions (around 2002, 2012, 2016 and 2020), so take care with long-term trends.
• The user guide notes missing days in the SeaWiFS-only period (1997–2000) and that major events such as the January 2022 Hunga Tonga–Hunga Ha'apai eruption can cause chlorophyll anomalies.
• Do not mix v6.0, v5.0, v5.0.1, v4.2 and other versions: input sensors, reprocessing and algorithms differ. In the C3S CDS, v5.0 had a reflectance jump in December 2020 to February 2021 that was fixed in v5.0.1.
• L3 composites are not gap-filled. The FAQ explains that gap-filled L4 data have poorer error characteristics than L3, so none are provided. If you need gap-free daily fields, consider the GlobColour gap-free products from Copernicus Marine.
• The C3S CDS release holds chlorophyll and reflectance only. For Kd(490), IOPs, uncertainties or water classes, download from CEDA (through 2022) or the PML server.

Notices and change history¶

References for your paper¶

Dataset citation¶

OC-CCI v6.0 4 km collection (CEDA) — DOI 10.5285/5011d22aae5a4671b0cbc7d05c56c4f0

@misc{sathyendranath2023occciv6,
  author    = {Sathyendranath, S. and Jackson, T. and Brockmann, C. and Brotas, V. and Calton, B. and Chuprin, A. and Clements, O. and Cipollini, P. and Danne, O. and Dingle, J. and Donlon, C. and Grant, M. and Groom, S. and Krasemann, H. and Lavender, S. and Mazeran, C. and M{\'e}lin, F. and M{\"u}ller, D. and Steinmetz, F. and Valente, A. and Z{\"u}hlke, M. and Feldman, G. and Franz, B. and Frouin, R. and Werdell, J. and Platt, T.},
  title     = {{ESA} Ocean Colour Climate Change Initiative ({Ocean\_Colour\_cci}): Version 6.0, 4km resolution data},
  year      = {2023},
  publisher = {NERC EDS Centre for Environmental Data Analysis},
  doi       = {10.5285/5011d22aae5a4671b0cbc7d05c56c4f0}
}

C3S CDS release (including extensions from 2023 onward) — DOI 10.24381/cds.f85b319d

@misc{c3s2019oceancolour,
  author    = {{Copernicus Climate Change Service}},
  title     = {Ocean colour from 1997 to present derived from satellite observations},
  year      = {2019},
  publisher = {Copernicus Climate Change Service (C3S) Climate Data Store (CDS)},
  doi       = {10.24381/cds.f85b319d}
}

Reference papers¶

Main OC-CCI reference — DOI 10.3390/s19194285

@article{sathyendranath2019occci,
  author  = {Sathyendranath, Shubha and Brewin, Robert and Brockmann, Carsten and Brotas, Vanda and Calton, Ben and Chuprin, Andrei and others},
  title   = {An Ocean-Colour Time Series for Use in Climate Studies: The Experience of the Ocean-Colour Climate Change Initiative ({OC-CCI})},
  journal = {Sensors},
  volume  = {19},
  number  = {19},
  pages   = {4285},
  year    = {2019},
  doi     = {10.3390/s19194285}
}

Acknowledgements¶

The ESA data page asks users to acknowledge that "The European Space Agency (ESA) Climate Change Initiative (CCI) Ocean Colour data are developed and produced" with funding and resources from ESA, the Copernicus Climate Change Service (C3S) and the NERC EO Data Analysis and AI Service (NEODAAS), to cite Sathyendranath et al. (2019), and to cite the DOI of the version used. It also asks that publications be reported to the OC-CCI team (help@esa-oceancolour-cci.org).

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• ESA CCI — Ocean Colour project
• ESA CCI — Ocean Colour data and citation guidance
• oceancolour.org — FAQ
• OC-CCI Product User Guide v6.5 (docx)
• C3S CDS — Ocean colour from 1997 to present
• This site — Copernicus-GlobColour ocean colour (Copernicus Marine)
• This site — MODIS ocean colour
• This site — VIIRS ocean colour
• This site — PACE OCI
• This site — GOCI-II