EMIS - MERIS Monthly gradients sea surface Chlorophyll-a concentration (2km) (ratio)

Collection: EMIS : Environmental Marine Information System 


Monthly gradients sea surface Chlorophyll-a concentration (ratio(log10) at 2km resolution) derived from the MERIS sensor (Satellite remote sensing Ocean color data):

Chlorophyll is a photosynthetic pigment commonly present in all phytoplankton species. It is used as a proxy for phytoplankton biomass.

Chlorophyll concentration is a standard product from satellite-based optical sensors, usually retrieved from empirical algorithms using reflectance ratios at two or more wavebands.


jrc-emis (at)


  • Frederic Melin

How to cite

Melin, Frederic (2016): EMIS - MERIS Monthly gradients sea surface Chlorophyll-a concentration (2km) (ratio). European Commission, Joint Research Centre (JRC) [Dataset] PID:


coastal environment GIS digital format marine environment marine monitoring ocean color satellite observations climate change sea surface Chlorophyll-a concentration gradients sea water protection

Data access

EMIS - Download access (EMIS_M_GRA_CHLA)
  • Direct NetCDF download

Spatial coverage

Type Value
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<gml:Polygon xmlns:gml="">  <gml:exterior>    <gml:LinearRing>      <gml:posList>-30 70 42 70 42 10 -30 10 -30 70</gml:posList>    </gml:LinearRing>  </gml:exterior></gml:Polygon>
POLYGON ((-30 70, 42 70, 42 10, -30 10, -30 70))

Temporal coverage

From date To date
2002-05-01 N/A

Lineage information

General information: Monthly gradients sea surface Chlorophyll-a concentration (ratio log10 scalling) derived from the MERIS sensor. Processing information: Chlorophyll-a data is processed using NASA SeaDAS 6.4 software and the standard OC3M algorithm for chla. Temporal characteristics: This product consists of standard monthly gradients sea surface chlorophyll-a concentrations (L3 product) at 2km resolution (projection: Equidistant cylindrical Grid mapping: equirectangular). Description of observation methods/instruments: The remote sensing of 'Ocean Color' represents a measure of the spectral variations in the light leaving the water surface, subsequently interpreted in terms of concentrations of optically-significant constituents in the water. After removing the atmospheric contribution, the water leaving radiance recorded at a given time and wavelength by the satellite reflects the optical properties of the water which, in turn, mirrors a specific structure and biogeochemical composition of the marine waters. Accordingly, the satellite-derived reflectance at the air-sea interface can be related to the concentration of an optically-significant constituent (e.g. chlorophyll). The retrieval of chlorophyll from SeaWiFS for case 1 waters (optically dominated by phytoplankton and associated products) uses a 4th order polynomial algorithm (O'Reilly et al. 2000). Quality/accuracy/calibration information: The 'standard' algorithm proposed by space agencies to process data from their sensors has a nominal accuracy of ~35% in the retrieval of surface chlorophyll in case 1 waters. References: J. E. O'Reilly and co-authors, SeaWiFS Postlaunch Calibration and Validation Analyses, Part 3. NASA Tech. Memo. 2000-206892, Vol. 11, S.B. Hooker and E.R. Firestone, Eds., NASA Goddard Space Flight Center, Greenbelt, Maryland, 9-23. Other contextual information: The product is stored in NetCDF data and available for download.

Additional information

Published by
European Commission, Joint Research Centre
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