Reports of the International Ocean-Colour Coordinating Group An Affiliated Program of the Scientific Committee on Oceanic Research (SCOR) Supporting the Committee on Earth Observing Satellites (CEOS) IOCCG Report Number 2, 1999 Status and plans for Satellite Ocean-Colour Missions: Considerations for Complementary Missions. Report of an IOCCG working group held in Halifax, Nova Scotia, Canada, June 16-18, 1998, chaired by Mr. Tasuku Tanaka (NASDA). Edited by James A. Yoder (URI); Based on contributions from: Watson W. Gregg, Nicolas Hoepffner, John Parslow, Trevor Platt, Michael Rast, Shubha Sathyendranath, Tasuku Tanaka and James A. Yoder. Please cite this report as IOCCG (1999), with the complete bibliographic citation as follows: IOCCG (1999). Status and Plans for Satellite Ocean-Colour Missions: Considerations for Complementary Missions. Yoder, J. A. (ed.), Reports of the International Ocean-Colour Coordinating Group, No. 2, IOCCG, Dartmouth, Canada. ISSN: 1098-6030 The International Ocean-Colour Coordinating Group (IOCCG) is an international group of experts in the field of satellite ocean colour, which acts as a liaison and communication channel between users, managers and agencies in the ocean-colour arena. The IOCCG is sponsored by NASA (National Aeronautics and Space Administration), NASDA (National Space Development Agency of Japan), ESA (European Space Agency), CNES (Centre National d’Etudes Spatiales), JRC (Joint Research Centre, EC), Canadian Space Agency (CSA), and SCOR (Scientific Committee on Oceanic Research). http://www.ioccg.org Published by the International Ocean-Colour Coordinating Group, PO Box 1006, Dartmouth, Nova Scotia, Canada, B2Y 4A2 Printed by MacNab Print, Dartmouth, Canada © IOCCG 1999 Contents Executive Summary ................................................................................................................ 1 1. Introduction ..................................................................................................................5 2. Utility of Ocean-Colour Data ........................................................................................ 7 2.1 Ocean Carbon Flux ............................................................................................... 7 2.2 Ocean Biology and Upper Ocean Processes ........................................................... 8 2.3 Scientific Analysis and Management of the Coastal Zone ...................................... 8 3. Technical Requirements for Satellite Ocean-Colour Sensors .......................................... 11 3.1 Technical Requirements for Open-Ocean, Global Missions ................................... 12 3.2 Technical Requirements for Coastal Applications .................................................. 14 3.3 Technical Requirements for New and Emerging Applications of Ocean-Colour Data ........................................................................................... 17 3.4 New Technologies in Ocean Colour ...................................................................... 22 3.5 Meeting the Requirements ..................................................................................... 23 4. Assessment of Existing and Planned Sensors up to Approximately the Year 2005........... 25 4.1 Assessment of Sensors for Minimum Requirements ............................................... 25 4.2 Global Coverage .................................................................................................... 25 4.3 Latitudinal Coverage.............................................................................................. 26 4.4 Temporal Coverage ................................................................................................ 28 5. Data Merging and Validation......................................................................................... 30 5.1 Data Merging and Integration ............................................................................... 30 5.2 Validation .............................................................................................................. 32 5.3 Integration ............................................................................................................. 33 6. Steps Towards Developing a Strategy to Coordinate Ocean-Colour Measurements from Space in the Post-2005 Timeframe ................................................. 34 6.1 Introduction .......................................................................................................... 34 6.2 Tentative Plans for Future (Post-2005) Ocean-Colour Sensors .............................. 35 6.3 Strategy for the Post-2005 Timeframe.................................................................... 36 References .............................................................................................................................. 39 List of Acronyms and Abbreviations ....................................................................................... 42 Executive Summary • 1 Executive Summary This report explains the utility of ocean- understand how it is controlled and why it colour data, summarizes technical require- varies from year to year. This is the province ments for global-scale, operational and of the marine programmes of the IGBP, and scientific remote sensing of ocean colour in ocean-colour remote sensing plays an both Case 1 (open-ocean) and Case 2 invaluable role in these programmes. It is (coastal) waters and addresses the issues of used as the basis of a method to compute complementarity that arise whenever more ocean primary production, and also to than one sensor with similar capabilities is provide the chlorophyll fields that can be in orbit at the same time. The objective is to used to initiate and verify coupled, numerical provide space agencies with the information models of the ocean and its embedded necessary for them to begin developing an ecosystem. Looking to the future, it will be internationally-coordinated plan for the used in earth-observing programmes such as uninterrupted delivery of ocean-colour data GOOS to detect changes in the structure into the indefinite future. and function of the ocean ecosystem that follow from the ensemble of forces that we The Utility of Ocean-Colour Data refer to collectively as climate change. We recognize here three broad scientific A second application of ocean-colour applications of ocean-colour data. The first data is to provide a synoptic, observational concerns the ocean carbon cycle, and the role link between the development of the ocean of the ocean in climate change. It is therefore ecosystem and the physics of the mixed layer. of profound significance in the response of Because phytoplankton control the optical governments and agencies to the Kyoto turbidity in most parts of the ocean, they Protocol. A primary goal of ocean-colour control the manner in which the mixed layer remote sensing is to produce synoptic fields heats up under the influence of the sun. of chlorophyll pigment, an index of Physical models of the mixed layer include phytoplankton biomass. It is the single most a balance between the onset of stratification important property of the marine ecosystem through heating and the erosion of that we would like to measure at synoptic stratification through turbulence. Optical scales. Phytoplankton consume carbon turbidity is a key property in these models, dioxide in their basic nutrition (photo- and it can be delivered synoptically from synthesis). On a global scale, marine phyto- ocean-colour remote sensing. Mixed-layer plankton consume fifty thousand million models seek to predict sea-surface temper- tonnes of carbon every year in a process ature, critical for weather forecasting in referred to as primary production. maritime areas, especially in the tropics. Thus, ocean-colour data will be important One of the aims of climate research in in IGOS programmes such as GODAE, and the ocean is to quantify this carbon flux, to will be important more widely in earth- 62 • Status and Plans for Satellite Ocean-Colour Missions observing programmes such as GOOS. v Local-scale data are collected with a resolution of 1 km or better. They are The third application of ocean-colour especially useful for coastal or Case 2 data that we mention here is the general area waters, and are of particular interest to of coastal zone management, including programmes such as GLOBEC, LOICZ fisheries management. One of the central and HAB. questions in fisheries science today is the extent to which fluctuations in the biomass The requirements of typical applications of exploited stocks can be accounted for by at these two principal scales are different, and fluctuations in the ecosystem consequent they will be treated sequentially in this upon variations in the large-scale circulation. report. It is a question that can be addressed only with the aid of a time series of synoptic views Principal Mission Types of the ocean ecosystem as supplied by ocean- colour remote sensing. One of the tragedies Another way to classify ocean-colour of modern biological oceanography is that, initiatives is according to the mission type. at a time when major fish stocks were failing The most fundamental differences are around the world, there was no stream of between operational missions that support ocean-colour data available that could have government programmes (such as the been utilized in discussion of these matters. meteorological satellites supporting weather- Beyond fisheries issues, ocean-colour data