Ocean Colour CCI

The Ocean Colour CCI (OC_CCI) project focuses on the Ocean Colour ECV encompassing water-leaving radiance in the visible domain, derived chlorophyll and inherent optical properties and will utilise data archives of from ESA’s MERIS and NASA’s SeaWiFS, MODIS and possibly CZCS (after careful evaluation) sensors archives. It is also looking at the feasibility of using OCM-2 and VIIRS data as a "gap filler" before the launch of Sentinel-3.

Version 4 Dataset Release

The latest version of the OC-CCI dataset is 4.0 that comprises of globally merged MERIS, Aqua-MODIS, SeaWiFS and VIIRS data with associated per-pixel uncertainty information. This is an update of the version 3.1 product that includes NASA's most recent reprocessing (R2018) updates for MODIS-Aqua, VIIRS and SeaWiFS.  This included significant recalibration for MODIS to address noticeable drift in trends resulting from sensor decay. 

The dataset is periodically being updated, and the June 2019 release of version 4.0 extends the dataset to the end of December 2018.

Downloading and extracting data

Access to several options, including FTP and the Composite Browser, is available via http://www.oceancolour.org/

The data can be directly downloaded from: ftp://oc-cci-data:ELaiWai8ae@oceancolour.org/

FTP server: oceancolour.org
Username: oc-cci-data
Password: ELaiWai8ae

Support is available from help@esa-oceancolour-cci.org

Some people have reported that the Mac FTP client has trouble with files bigger than 4GB. If you look at the monthly composites directory and the files there appear to be around 500-600MB rather than ~4.5GB, you're affected by this problem. If you attempt to download, you'll get ~500MB corrupt files. So you'll need to use an alternative FTP client or the terminal.

If you’re interested in downloading a subset of the dataset then THREDDS provides several options. As an example, the NetCDF subset service allows for a spatial and / or temporal subset to be extracted.

From https://rsg.pml.ac.uk/thredds/catalog-cci.html first choose the temporal composites required (daily, 8day or monthly) and then access Option 5, which is NetcdfSubset. Now choose the products, Latitude / Longitude subset and time subset options. Then press Submit at the bottom of the page.

If you receive an error message then it’s likely you’re trying to download too much data in one block – files cannot be larger than 4GB. The Stride parameter can be set to a value greater than 1 if you only want every nth value.

The output is a single NetCDF file and so this method will become unwieldy for large areas / time periods.If you’d prefer binary or ASCII data then choose Option 1, which is OPeNDAP.

To browse the data in an interactive viewer then the Web GIS Portal (http://www.oceancolour.org/portal/) is an option that can produce plots / graphics of the data as well as also exporting layers. First select the product(s) that you’re interested in, then select ‘Analysis’ that should be in the top right hand corner and choose what you’d like to do.