Global Reprocessed Observation Product For the Atlantic and Arctic Observation Products OCEANCOLOUR_GLO_OPTICS_L3_REP_OBSERVATIONS_009_064 OCEANCOLOUR_GLO_CHL_L3_REP_OBSERVATIONS_009_065 OCEANCOLOUR_GLO_CHL_L4_REP_OBSERVATIONS_009_093 Issue: 2.1 ContriButors: S. Pardo, T. Jackson, B. Taylor, J. Netting, B. Calton, B. Howey Approval Date by Quality Assurance Review Group : 05/01/2021 QUID for the OC TAC Products Ref : CMEMS-OC-QUID-009-064-065-093 Global Reprocessed Observation Date : 10/09/2020 Issue : 2.1 CHANGE RECORD Issue Date § Description of Change Author Validated By 1.0 01/05/2015 all First version of document M. Taberner, S L. Crosnier Pardo, S. Groom, R. Brewin, T. Jackson 1.1 26/01/2016 all ARV2 version R. Brewin, S. Pardo, T. Jackson, M. Grant, B.Taylor 1.2 04/94/2916 all Changes for V2 ARR R. Brewin, S. Pardo, T. Jackson, M. Grant, B.Taylor 1.3 18/01/2016 all Changes for V3 S. Pardo, M. Grant, T. Jackson 1.4 24/03/2017 all V3 answer to review S. Pardo 1.5 21/11/2017 all Changes for V3.3 B. Taylor 1.6 25/01/2018 all Changes for V4 B. Taylor 1.7 23/05/2018 all July Service Release B. Taylor 2.0 04/09/2019 all December 2019 Service Release S. Pardo, J. Netting, Mercator Ocean B. Calton 2.1 10/09/2020 all December 2020 Service Release S. Pardo, J. Netting, Vittorio Brando, B. Calton, B. Howey Shubha Sathyendranath Page 2/ 25 QUID for the OC TAC Products Ref : CMEMS-OC-QUID-009-064-065-093 Global Reprocessed Observation Date : 10/09/2020 Issue : 2.1 TABLE OF CONTENTS EXECUTIVE SUMMARY ............................................................................................................................................. 4 Products covered By this document .................................................................................................................... 4 Summary of the results ........................................................................................................................................ 5 Estimated Accuracy NumBers .............................................................................................................................. 6 PRODUCTION SUBSYSTEM DESCRIPTION ................................................................................................................ 7 Production Centre: Ocean Colour Thematic AssemBly Centre .......................................................................... 7 Production suBsystem: PU: OC-PML-PLYMOUTH-UK ......................................................................................... 7 The ESA Ocean Colour Climate Change Initiative (OC-CCI) Processor at PML ................................................... 7 The PFT Processor at PML ............................................................................................................................. 10 VALIDATION FRAMEWORK .................................................................................................................................... 11 Introduction ....................................................................................................................................................... 11 Off-line (in situ) Validation ................................................................................................................................ 11 VALIDATION RESULTS ............................................................................................................................................. 14 SYSTEM’S NOTICEABLE EVENTS, OUTAGES OR CHANGES .................................................................................... 22 QUALITY CHANGES SINCE PREVIOUS VERSION ..................................................................................................... 23 REFERENCES ............................................................................................................................................................ 24 Page 3/ 25 QUID for the OC TAC Products Ref : CMEMS-OC-QUID-009-064-065-093 Global Reprocessed Observation Date : 10/09/2020 Issue : 2.1 EXECUTIVE SUMMARY Products covered by this document This document covers the CMEMS global, reprocessed, observation dataset (GLO REP). The input dataset for the production of GLO REP was made available to CMEMS by the ESA Ocean Colour Climate Change Initiative (ESA OC-CCI) project. The OC-CCI project developed and implemented a method of band-shifting, bias-correcting and merging data from multiple ocean colour sensors: SeaWiFS (GAC and LAC), MODIS Aqua, MERIS and VIIRS (OC- CCI 2014a), and in the latest version of CCI, OLCI-3A. The performance of the available atmospheric correction and in-water algorithms was assessed in an open process and the best performing algorithms were selected according to published criteria (OC-CCI 2014b, OC-CCI 2014c). The initial OC-CCI system was developed as described in OC-CCI 2012, and has been updated in every subsequent version. The resulting global products were validated by OC-CCI; compared to the time series of individual sensor data; and compared to the GlobColour dataset (OC-CCI 2014d). A summary of OC-CCI products is provided in Sathyendranath et al. (2019). The CMEMS REP products described in this document have been generated from the most recent OC-CCI v5 dataset, which incorporates the latest NASA reprocessing (NASA R2018.0) for MODIS, VIIRS and SeaWiFS data. The input dataset for the global product is provided at a nominal 4 km resolution on a rectangular grid (0.0416o/pixel) using the OC-CCI processing chain. All input products were daily composites created by accumulating all data from a given sensor for a particular day, band-shifting and bias-correcting SeaWiFS, MODIS- Aqua, VIIRS and OLCI-3A bands to the MERIS bands, and 'merging' all data available for that day (whether from SeaWiFS, VIIRS, MODIS-Aqua, OLCI-3A and/or MERIS). The OCEANCOLOUR_GLO_OPTICS_L3_REP_OBSERVATIONS_009_064 product is composed of a subset of remote sensing reflectances (bands 412, 443, 490, 510, 560 and 665) that are directly extracted from those input daily composites and repackaged for compliance with the CMEMS format standards. The OCEANCOLOUR_GLO_CHL_L3_REP_OBSERVATIONS_009_065 product contains the chlorophyll concentration variable, directly extracted from the input OC-CCI daily composites and repackaged for compliance with the CMEMS format standards. The chlorophyll algorithm used in OC-CCI is a blend of OC2, OCx, OCI and OCI2, applied to the reflectances, with the blend proportion dependent on the membership of various water types in the pixel in question (Jackson et al., 2017). The algorithms used are chosen on the basis of extensive round-robin exercises (OC-CCI 2014c; Brewin et al. 2015a, Müller et al. 2015a,b) that considered both quantitative analyses against in situ data and qualitative considerations obtained from user consultations, such as meeting GCOS requirements for error characteristics (OC-CCI 2014c). The criteria were developed to meet the requirements for climate quality data (Sathyendranath et al. 2017). From December 2019 on, the OCEANCOLOUR_GLO_CHL_L3_REP_OBSERVATIONS_009_065 product also contains the CMEMS phytoplankton functional type (PFT) variables expressed as chlorophyll concentration in sea water contained in three size classes: Micro (Micro-phytoplankton), Nano (Nano-phytoplankton) and Pico (Pico- phytoplankton). Note that, in the global products, the functional types are grouped according to size (Vidussi et al., 2001), with microplankton representing phytoplankton types with nominal sizes greater than 20 μm (for example, diatoms and dinoflagellates), nano-phytoplankton with sizes in the 2-20 μm range (for example, nanoflagellates and cryptophytes), and the picophytoplankton grouping small cells of less than 2 μm in nominal size (for example, Synechococcus and Prochlorococcus). Hence it would be also appropriate to refer to these classes as “Phytoplankton Size Class” (PSC) variables. The PFT products are made available at 4 km resolution following Brewin et al. (2015b). The OC-CCI Rrs have also been provided at the CMEMS regional level (1 km) and the regional algorithms applied to retrieve chlorophyll concentrations. Quality information for the regional algorithms is available in the corresponding regional QUID (CMEMS-OC-QUID-009-066-067-068-069-088-091). The OC-CCI project came to an end in 2018. Production of ECVs (essential climate variables) based on the OC-CCI method will be continued as part of the Copernicus Climate Change Service (C3S), while R&D activities will carry QUID for the OC TAC Products Ref : CMEMS-OC-QUID-009-064-065-093 Global Reprocessed Observation Date : 10/09/2020 Issue : 2.1 on within the framework of ESA’s CCI+. This means that documentation and products will be added and will evolve over time. Differing timelines between CMEMS and OC-CCI/C3S/CCI+ mean that new or updated documentation might be made available by ESA/Copernicus, which supersedes or augments the information presented here. The user is, therefore, referred to the OC-CCI (www.esa-oceancolour-cci.org), C3S and CCI+ websites for more detailed information and documentation. The development of the PFT variables at the regional scale (for the Atlantic) is based on the results of the TOSCA (Towards Operational Size-class Chlorophyll Assimilation) project funded through the CMEMS Service Evolution 21-SE-CALL1 (Ciavatta et al., 2018), whereas the global products described here are based on Brewin et al. (2015b), because the algorithm described in Brewin et al. (2015b) has been validated at