Action #3: Optical data for Ocean Colour product validation

Objectives: Ocean Colour algorithm development and product validation benefit largely from in situ measurements of optically active compounds, their concentrations and/or specific optical properties, and match-up (synoptic) measurements at different sites. Key challenges with some optical sensors (fluorescence, turbidity) are that results are not clearly traceable and in effect, they are represented in the relative scale. The lack of standards for sensors and their calibration and validation makes the intercomparison between sensors difficult. This task builds on the results of GoF PSS #1, inter-calibration between sensors and improved QC. It provides Regional Data, as consistent as possible within technological limits, to Ocean Colour groups for evaluation.

Action Lead and other Partners (with contact persons): SYKE (Seppälä, Ylöstalo), TALTECH (Liblik, Salm)

JS3 Platforms included: FerryBox: Silja Serenade and Finnmaid (SYKE), Silja Europa (TALTECH), Utö Observatory (SYKE), Keri Observatory (TALTECH); calibration lab (SYKE).

Other data sources and external partners for implementation: Ocean Color data from Sentinel satellites. Work includes remote sensing groups of participating partners.  

Overall timetable of action: January 2021 – August 2022

Description of action: Optical sensor measurements of aquatic optically active compounds are often rather incomparable between actors, due to lack of standardised methods. This hinders the use of such data for Ocean Colour match-ups and ground-truthing. To improve the use of multisource sensor data, joint steering of the sensor QA/QC and sharing sensor validation practices and data are required. This topic will demonstrate transnational collaborations in the production of multisensor data. 

The practical actions include sensor intercomparison workshops (winter 2021 & 2022, jointly with GoF PSS #1). Optical multisensor data will be collected in 2021 at fixed platforms and FerryBoxes, including optical proxy measurements (Chla and CDOM fluorescence), measurements of inherent optical properties (absorption, scattering) and specific inherent optical properties for water quality parameters (algae, CDOM).     

Best practices used or developed: For optical measurements, we aim to follow best practices developed for satellite ocean colour sensor validation by The International Ocean-Colour Coordinating Group (IOCCG). Their further adjustments for Baltic conditions will be done as needed.

Data flows: Primary data from FerryBoxes flows to EMODnet Physics and CMEMS. Fixed Station data and data from exploratory sensors remain at the hosting institutes and is available on request. Opening these datasets is desirable via VA (WP11) during the PSS implementation, through developments made in WP7 T7.5 D2PTS,

Data QC routines: New steps in operational data QC protocols are required for temperature compensation of CDOM fluorescence and for spike detection of Chla fluorescence.  

Data management issues: A review of data vocabularies needs to be carried out, as data measured with various methods and sensors are not directly comparable.    

Expected results: The topic will provide evidence of how using Regional Data and shared QC of optical measurements decrease uncertainties in their use in EO product validation. Secondly, the topic provides improved estimates of how well the sensor data (fluorescence) describes the actual variability of the phytoplankton and CDOM abundance in the Baltic Sea as estimated by satellite data or traditional laboratory methods.    

Users of results: Ocean Colour community

Dissemination of results: Dissemination is primarily targeted to remote sensing groups in the Baltic Sea, via participation in workshops, seminars and by targeted contacting groups asking them to evaluate the data for scientific use. 

Links: Action will open a dialogue with WP 2, T2.3 on how the JERICO-RI observations may be promoted to the Ocean Colour community.