Copernicus-GlobColour¶

Global Ocean Colour (Copernicus-GlobColour), Bio-Geo-Chemical, L3 (daily) / L4 (monthly and interpolated) from Satellite Observations (Copernicus Marine; MY OCEANCOLOUR_GLO_BGC_L3_MY_009_103 and L4_MY_009_104, NRT L3_NRT_009_101 and L4_NRT_009_102)

Available

At a glance¶

Note on period: MY multi-sensor data start on 1997-09-04 (L4 monthly in 1997-09) and OLCI-only data on 2016-04-25. NRT holds only the recent period (when checked on 2026-10-13, the NRT L3 collection started 2023-04-25 and the 202411 multi-sensor chlorophyll dataset 2024-09-30). Some days are missing in the SeaWiFS-only period (1997–2002), and phytoplankton functional types (PFT) are not available before 2002.

Overview¶

Global ocean-colour biogeochemical data produced by the Copernicus Marine Ocean Colour TAC with ACRI-ST's Copernicus-GlobColour processor. There are 4 km multi-sensor products merging SeaWiFS, MODIS, MERIS, VIIRS (SNPP, NOAA-20, NOAA-21) and OLCI (S3A, S3B), and OLCI-only 4 km and 300 m products, covering chlorophyll-a, phytoplankton functional types and size classes, remote-sensing reflectance, Kd(490), transparency (Secchi depth), suspended matter, backscattering, coloured dissolved organic matter and primary production. Chlorophyll is computed per sensor and then merged, unlike OC-CCI, which merges reflectance first. Separate near-real-time (NRT, available the day after observation) and multi-year (MY, from 1997) products are provided.

What changes with the successor¶

GlobColour version 202603 → GlobColour version 202611 Planned¶

Transition: 2026-11

A dataset version change within the same products. Multi-sensor chlorophyll, transparency and primary production are reprocessed with updated OC5 coefficients, and carbon datasets and new variables are added.

Sources: Copernicus Marine product roadmap — L4_MY_009_104 · Copernicus Marine product roadmap — L3_NRT_009_101

Available variables¶

Variable names and units follow the Copernicus Marine dataset metadata (STAC, versions 202603 and 202411). The multi-sensor 4 km datasets are split into five groups: plankton (chlorophyll and PFT), reflectance, optics (BBP, CDM), transp (KD490, SPM, ZSD) and pp (primary production). OLCI-only datasets have more reflectance bands (400–709 nm, per the product description).

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

Chlorophyll and phytoplankton (plankton, L3 daily / L4 monthly)¶

Remote-sensing reflectance (reflectance, multi-sensor 4 km)¶

Optics and transparency (optics, transp)¶

Primary production (pp, L4 monthly only)¶

Gap-free daily data (L4 gap-free, multi-sensor 4 km)¶

The full variable list is in the official documentation.

How to get the data¶

• Copernicus Marine — MY L3 daily (OCEANCOLOUR_GLO_BGC_L3_MY_009_103) — Copernicus Marine Toolbox (copernicusmarine subset, get, open_dataset) / web download and subsetting
  • Dataset IDs include cmems_obs-oc_glo_bgc-plankton_my_l3-multi-4km_P1D, cmems_obs-oc_glo_bgc-reflectance_my_l3-multi-4km_P1D, cmems_obs-oc_glo_bgc-transp_my_l3-multi-4km_P1D, cmems_obs-oc_glo_bgc-optics_my_l3-multi-4km_P1D, and for OLCI …_my_l3-olci-4km_P1D and …_my_l3-olci-300m_P1D. Downloads require signing in (a free Copernicus Marine account or a Copernicus Data Space account).
• Copernicus Marine — MY L4 monthly and gap-free daily (OCEANCOLOUR_GLO_BGC_L4_MY_009_104) — Copernicus Marine Toolbox / web
  • Monthly cmems_obs-oc_glo_bgc-plankton_my_l4-multi-4km_P1M, primary production cmems_obs-oc_glo_bgc-pp_my_l4-multi-4km_P1M, gap-free daily cmems_obs-oc_glo_bgc-plankton_my_l4-gapfree-multi-4km_P1D, daily climatology cmems_obs-oc_glo_bgc-plankton_my_l4-multi-climatology-4km_P1D, and others.
• Copernicus Marine — NRT L3 daily (OCEANCOLOUR_GLO_BGC_L3_NRT_009_101) — Copernicus Marine Toolbox / web
  • Delivered the day after acquisition at 22:00 UTC. Dataset IDs replace my with nrt (e.g. cmems_obs-oc_glo_bgc-plankton_nrt_l3-multi-4km_P1D).
• Copernicus Marine — NRT L4 monthly and gap-free daily (OCEANCOLOUR_GLO_BGC_L4_NRT_009_102) — Copernicus Marine Toolbox / web
  • For example cmems_obs-oc_glo_bgc-plankton_nrt_l4-gapfree-multi-4km_P1D and cmems_obs-oc_glo_bgc-pp_nrt_l4-multi-4km_P1M.

Example code¶

Downloads MY L4 monthly chlorophyll for the seas around Korea with the Copernicus Marine Toolbox. Run copernicusmarine.login() once to store your credentials. Around a dataset version change (e.g. 2026-11), you can pin dataset_version to keep results reproducible.

# pip install copernicusmarine xarray
import copernicusmarine
import xarray as xr

copernicusmarine.login()   # once only (stores username and password)
copernicusmarine.subset(
    dataset_id="cmems_obs-oc_glo_bgc-plankton_my_l4-multi-4km_P1M",
    variables=["CHL", "CHL_uncertainty"],
    minimum_longitude=120, maximum_longitude=132,
    minimum_latitude=30, maximum_latitude=40,
    start_datetime="2024-01-01", end_datetime="2024-12-31",
    output_filename="globcolour_chl_korea_2024.nc",
)
ds = xr.open_dataset("globcolour_chl_korea_2024.nc")
print(ds["CHL"].mean(["latitude", "longitude"]).values)

Practical tips¶

• The PUM notes that GlobColour MY may contain time-series inconsistencies from upstream sensor recalibrations and processing changes, while OC-CCI, designed for inter-sensor consistency, does not extend to the present. Consider OC-CCI for long-term trends and GlobColour for recent and near-real-time monitoring.
• In the multi-sensor data, MODIS was dropped from early 2023 and VIIRS-NOAA21 added from November 2022 (version 202603). Coverage and values may shift around these dates.
• The QUID states that reprocessing can change values by more than 20% in some regions. Record the dataset ID and version (from the file and your download date) in papers, and do not mix versions.
• In turbid waters such as the coastal Yellow Sea and East China Sea, OC5 applies an adaptation for complex waters, but suspended matter (SPM) and CDM may dominate the optics more than chlorophyll. Check SPM, CDM and the uncertainties together.
• Gap-free daily data are interpolated. Cells with flags equal to 2 (INTERPOLATED) are not actual observations, so for short-lived events such as harmful algal blooms use L3 daily data or values filtered by flags.
• The 300 m OLCI products help in coastal work but start only on 2016-04-25, and their algorithms and sensors differ from the multi-sensor 4 km data, so do not mix them.
• Primary production PP relies on model and analysis inputs such as GLORYS12V1 mixed layer depth and OSTIA SST; the QUID notes that in situ validation is limited (r² about 0.63).
• Version 202611 is due on 2026-11-24, when some 202603 datasets are scheduled to retire (STAC metadata). The double-dissemination period is announced as 2026-11-03 to 2027-01-12, so check your scripts before then.

Notices and change history¶

References for your paper¶

Dataset citation¶

MY L3 daily (OCEANCOLOUR_GLO_BGC_L3_MY_009_103) — DOI 10.48670/moi-00280

@misc{cmems_oc_glo_l3_my,
  author    = {{E.U. Copernicus Marine Service Information (CMEMS)}},
  title     = {Global Ocean Colour (Copernicus-GlobColour), Bio-Geo-Chemical, L3 (daily) from Satellite Observations (1997-ongoing)},
  publisher = {Marine Data Store (MDS)},
  doi       = {10.48670/moi-00280}
}

MY L4 monthly and gap-free (OCEANCOLOUR_GLO_BGC_L4_MY_009_104) — DOI 10.48670/moi-00281

@misc{cmems_oc_glo_l4_my,
  author    = {{E.U. Copernicus Marine Service Information (CMEMS)}},
  title     = {Global Ocean Colour (Copernicus-GlobColour), Bio-Geo-Chemical, L4 (monthly and interpolated) from Satellite Observations (1997-ongoing)},
  publisher = {Marine Data Store (MDS)},
  doi       = {10.48670/moi-00281}
}

NRT L3 daily (OCEANCOLOUR_GLO_BGC_L3_NRT_009_101) — DOI 10.48670/moi-00278

NRT L4 monthly and gap-free (OCEANCOLOUR_GLO_BGC_L4_NRT_009_102) — DOI 10.48670/moi-00279

Reference papers¶

GlobColour chlorophyll merging and flagging — DOI 10.5194/os-15-819-2019

@article{garnesson2019globcolour,
  author  = {Garnesson, Philippe and Mangin, Antoine and Fanton d'Andon, Odile and Demaria, Julien and Bretagnon, Marine},
  title   = {The {CMEMS} {GlobColour} chlorophyll a product based on satellite observation: multi-sensor merging and flagging strategies},
  journal = {Ocean Science},
  volume  = {15},
  number  = {3},
  pages   = {819--830},
  year    = {2019},
  doi     = {10.5194/os-15-819-2019}
}

Acknowledgements¶

Copernicus Marine recommends the sentence "This study has been conducted using E.U. Copernicus Marine Service Information;" followed by the DOI links of all products used.

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¶

• Copernicus Marine — OCEANCOLOUR_GLO_BGC_L3_MY_009_103
• Copernicus Marine — OCEANCOLOUR_GLO_BGC_L4_MY_009_104
• Ocean Colour Product User Manual (PUM, PDF)
• Quality Information Document QUID 009-101 to 104 (PDF)
• Copernicus Marine Toolbox documentation
• Copernicus Marine — how to cite
• This site — ESA OC-CCI (ocean colour climate record)
• This site — MODIS ocean colour
• This site — VIIRS ocean colour
• This site — PACE OCI
• This site — GOCI-II