Role of Ocean Colour in Biogeochemical, Ecosystem and Climate Modelling

Update: The final report form this working, entitled  Synergy between Ocean Colour and Biogeochemical/Ecosystem Models (IOCCG Report 19) will be published early in 2020. Hard copies of the report can be pre-ordered using the IOCCG Report Request Form.

Rationale

Numerical modellers are often listed as major users of ocean colour data. And yet there is relatively little communication between the ocean colour and the numerical modelling communities. From the ocean colour community’s perspective, it is important to know how numerical models use ocean colour data. In particular, what products are used and how they are used? How are uncertainties dealt with? From the numerical modelling community’s perspective queries are: What products are available? How to choose between different products of the same variable (e.g., Chl-a)? What are the uncertainties associated with each product? A dialogue between the two communities could address how models can be useful for the ocean colour community and how to reconcile model output with ocean colour products? Are there better methods to link satellite products and model output that draws on the best of each?

The rationale of this working group is to facilitate a better dialogue by bringing together a diverse group of numerical modellers with ocean colour specialists to synthesize current uses of ocean colour products, to provide a document that can be used by both communities in addressing the above questions, and lay out recommendations for continued and better use of ocean colour products in the future.

Terms of Reference

An initial set of questions (see below) will be addressed by the working group. These will be revisited as the working group progresses. Further information on each of these questions is given in the working group proposal.

• What types of models use ocean colour products? Each type of model will have distinct needs from ocean colour. Models can be designed to study the carbon cycle/biogeochemistry as well as ecosystems/ecosystem function. They can also be used in distinct ways, e.g., operational, identifying variability and trend (climate change), understanding processes such as spring bloom dynamics, and studying ecology (e.g., role of traits in setting community structure, role of predation etc.).
• What ocean colour products are being used? An informal survey in 2013 noted that Chl-a is the most commonly used ocean colour product, followed by primary production products. The qualitative use of PFTs has also been increasing over the last few years. A large scale survey of the numerical modelling community will be conducted by the working group.
• How do numerical modellers deal with ocean colour product uncertainty? The working group address will how the ocean colour community can better communicate the uncertainties in a manner that can be easily understood and used by the modelling community.
• How are ocean colour products being used in model evaluations? The working group will discuss techniques and potential “best practices” for model skill metrics specific for ocean colour products, including quantitative techniques.
• How is ocean colour data being used in data assimilation? The working group will identify the modelling groups that use ocean colour data and document which products are most beneficial (and when and where ocean colour products degrade the solution). Experts from the data assimilation community will also synthesize how ocean colour is currently being used and provide recommendations for both the ocean colour and data assimilation communities on the better use of these products.
• How can models help the ocean colour community? The working group will highlight past and current uses of models (e.g., how long the ocean colour times series should be to isolate trends from natural variability), as well as provide direction for the use of models in future ocean colour missions.
• How can clearer links between satellite products and model output be facilitated? The working group will identify the types of models that are currently resolving variables that can link with satellite products, explore potential links between the model output and satellite products, and provide recommendations on further developments that will enhance the use of ocean colour in models.
• Recommendations. A final outcome from this working group will be a set of recommendations of how the products could be better used. Such a set of recommendations is likely to include how the ocean colour community could better communicate what products are available, the uncertainties of each product, and which product is better for a specific purpose when several different products are available.

Working Group Members (in alphabetical order)

• Icarus Allen, PML, UK
• Mark Baird, CSIRO, Australia
• Fei Chai, University of Maine, USA
• Stephanie Dutkiewicz, (Chair) MIT, USA
• Marion Gehlen, IPSL/LSCE, CNRS, France
• Stephanie Henson, NOC, UK
• Colleen Mouw, University of Rhode Island , USA
• Cecile Rousseaux, Goddard, NASA, USA
• Charlie Stock, GFDL, NOAA, USA
• Anna Hickman, University of Southampton, UK
• Stefano Ciavatta, PML, UK