2nd CoastColour User Consultation Meeting
Frascati, Italy on 16 – 17 November, 2010
Uptake of ocean colour products in applied marine science and marine policy: a UK user perspective
This talk will show how various RS products from MarCoast I, MarCoast II and MyOcean are being used in many different ways by a governmental agency. Comparisons of chlorophyll, Kd and SPM products with corresponding in situ data sets for the North Sea will be shown. The needs of the Marine Strategy Directive will be presented in order to guide the new development of new products in CoastColour.
ODESA as a tool to support CoastColour validation
Constant Mazeran(1), Christophe Lerebourg(1), Odile Fanton d'Andon(1), Kathryn Barker(2), Samantha Lavender(2), Philippe Garnesson(1), Nicolas Gilles(1), Julien Demaria(1), Olivier Sardou(1), Gilbert Barrot(1), Ludovic Bourg(1), Philippe Goryl(3), Henri Laur(3)
(1) ACRI-ST, 260 route du Pin Montard, Sophia Antipolis, 06600, France
(2) ARGANS Limited Unit 3, Drake Building, Tamar Science Park, Plymouth, PL6 8BY, UK
(3) ESA/ESRIN Via Galileo Galilei CP 64, Frascati, Roma, 00044, Italy
The Optical Data processor of ESA (ODESA) intends to provide the scientific community a complete Level 2 processing environment for MERIS as well as for the future ESA optical sensors on board Sentinel 3.
This presentation will focus on MERMAID match-ups processing capabilities which could support the CoastColour validation.
We will give as well an overview of overall ODESA facilities, consisting of:
- A package made up of binary and source code of the Level 2 processor. A run & development platform allows the users to launch nominal and alternative processing (modification of both the source code and auxiliary data) on its own device.
- A validation facility: text files in MERMAID format containing Level 1b data with concurrent in-situ measurements can be processed through the same platform as any ENVISAT Level1b product.
- A remote mass processing facility for Level 3 validation, available to nominal and user's qualified versions approved by QWG.
- Analysis tools: new output parameters can be easily added through the interface and stored in ENVISAT format or netCDF3 or netCDF4, and visualised by BEAM.
- A dedicated forum in order to help and foster the ESA optical sensor community (announcement, data access, algorithms, products, …)
Variations of inherent optical properties in case of harbor dredging operations in Estonian coastal sea
Port development and maintenance in Estonian costal sea includes yearly dredging operations that increase the suspended matter (SPM) load into the coastal sea. The bottom sediments in Estonian coastal sea are different depending on the location of the port. We analyzed the optical properties of suspended particles in different locations during dredging operations. Field measurements were performed in 2008 and 2009. The vertical profiles of absorption and attenuation coefficient as well as of temperature, salinity and depth were measured with AC-spectra (WetLabs) and CTD (Seabird) in three different harbors in Estonian coastal sea. Also the concentrations of suspended particles and chlorophyll were determined from the water samples. One dataset also contains the measurements done near the sand mining area at the time of mining operations. Results show that the scattering and absorption spectra varies depending on the particles dominant in the water at the time of dredging. Cloud free MERIS images were also collected at the time of field work and processed with BEAM Case-2 regional processor. In the case when resuspended sediments were dominant particles in the sea area the MERIS TSM product described very precisely the situation in the study area.
Bio-optical monitoring of coastal Baltic Sea waters - from research to applications
Remote sensing and bio-optical parameters can be used as indicators for eutrophication and as diagnostic tool in coastal zone management. Quality controlled water quality maps have been derived for the NW Baltic Sea, and are implemented in an operational monitoring system. This is done in collaboration with the water quality project operated by Vattenfall Power Consultant (www.vattenkvalitet.nu). The leading idea is that the development in coastal remote sensing has now come to a stage, where we can start implementing the research results into operational monitoring systems, using certain optical parameters as prime indicators for water quality. Susanne Kratzer is coordinator of the Nordic Network in AquaticRemote Sensing (www.NordAquaRemS.org), and will also present recent activities within NordAquaRemS and the ESA MERIS coastal validation team.
Inversion of a semi-analytical reflectance model to retrieve inherent optical properties of the marine environment
E. Devred, S. Sathyendranath and T. Platt
Inherent optical properties of seawater influence the radiative field in the water column, and also various biological and physical processes. Given measurements of remote-sensing reflectance in multiple wavelengths, inversion techniques can be used to infer the inherent optical properties of various sea-water constituents: pure seawater, phytoplankton, yellow substances, detritus and non-organic particles (when present). In this work, we use the reflectance model of Sathyendranath and Platt (1997, 1998), which accounts for Raman scattering, along with a non-linear optimisation method, to retrieve the absorption and backscattering properties of the marine components from remote-sensing reflectances. The total absorption coefficient is formulated as the sum of the absorption coefficients of phytoplankton, yellow substances (including detritus) and pure seawater, whereas the backscattering coefficient is expressed as the sum of the backscattering coefficients of pure seawater and particles. The algorithm includes an original parameterisation of the Q factor as a function of the total absorption and backscattering coefficients. After optimization, differences between measured and modelled remote-sensing reflectances are exploited to infer changes in the spectral form of phytoplankton absorption, and hence phytoplankton size structure. Application of the algorithm to in situ and MERIS data over open and coastal waters is discussed.
In-situ evidence of non-zero SWIR reflectance in moderately turbid estuarine waters
Knaeps, E., Raymaekers, D., Sterckx, S. Ruddick, K.
The water-leaving reflectance in the SWIR is generally assumed to be zero, even for highly turbid waters. The idea is based on the high absorption of the pure water in this spectral region. This assumption has led to the development of atmospheric correction schemes for MODIS based on the SWIR (Wang, 2007, 2009). For more turbid waters this method provides an alternative to the NIR based approaches. Also the OLCI instrument on Sentinel 3 will provide data in this spectral range (OLCI band at 1020 nm).
In this presentation some evidence is presented of non-zero water-leaving reflectance between 1000 and 1150 nm. The first results are shown of a measurement campaign at the Scheldt river in Belgium. Water-leaving reflectance was measured with an ASD spectrometer in the range 350 to 2500 nm. Water samples were analyzed for their TSM concentration. The measurements give evidence that the SWIR black pixel assumption is not valid here between 1000 and 1150 nm and that backscattering by suspended particles influence the retrieved signal. The results were confirmed by simulations with the Gordon bio-optical model using IOPS from the Scheldt. Additionally hyperspectral APEX images were acquired over the study area, matching the in-situ water-leaving reflectance data. The APEX instrument provides data up to 2500 nm and the SWIR signals are currently under investigation.
A possible global partnership between ESA CoastColour project and JAXA Global Climate Observation Mission
H. Murakami, T. Hirata and the SGLI/GCOM Ocean Science Team
Japan Aerospace eXploration Agency (JAXA) has started the Global Change Observation Mission (GCOM) for a long-term monitoring (10-15 years) of global water cycles and climate change by means of satellite observation. The GCOM will run a series of satellites (3 satellites) from 2014 over the next 13 years, which carry the multi-channel optical sensor, namely Second generation GLobal Imager (SGLI). The SGLI wavebands extend from the near-UV (380nm) to thermal infrared (12ยตm) with spatial resolutions of 250m to 1km, hence the SGLI is suitable for coastal ocean colour observation. The SGLI/GCOM-C mission will conduct some science targets and activities similar to ESA CoastColour, therefore in situ data collection, algorithm development and Cal/Val activities under the SGLI/GCOM mission should be able to contribute to CoastColour project under a global partnership. For example, JAXA has been collecting in situ data for previous OCTS and GLI missions, and these data may be shared with CoastColour. In this presentation, the overview of GCOM and its current activities are introduced, and a possible contribution of GCOM/JAXA to CoastColour/ESA is discussed.
Validation of In Situ chlorophyll fluorescence in ferrybox system against laboratory analysis
Seppo Kaitala, Jukka Seppälä
During the phytoplankton growth period 2010 in theBaltic Sea with the ferrybox system including chlorophyll (Chla), phycocyanin (PC) and turbidity fluorometer, the records were collected during 61 transects of Finnmaid ferry cruising between Helsinki (Finland) and Travemunde (Germany). For the spring bloom, the chlorophyll florescence was validated with laboratory analysis of chlorophyll analysis from the corresponding water samples.Distribution of cyanobacteria cannot be evaluated using Chla in vivo fluorescence, as most of their Chla is located in nonfluorescing photosystem I. Phycobilin fluorescence, in turn, is noted as a useful tool in the detection of cyanobacterial blooms. PC in vivo fluorescence was compared with Chla in vivo fluorescence and turbidity measured simultaneously, and with Chla concentration and biomass of the bloom forming filamentous cyanobacteria determined from discrete water samples. PC fluorescence showed a linear relation to the biomass of the bloom forming filamentous cyanobacteria, and the other sources of PC fluorescence are considered minor in the open Baltic Sea.
Algorithm of chlorophyll-a concentrations retrieving from reflectance measurements in coastal zone of Black Sea
E.N. Korchomkyna, E.B. Shybanov, M.E. Lee
The method of chlorophyll concentration calculation using remote sensed ocean reflectance is proposed. This method can take into account the regional features of investigated basin, so it allows to avoid some errors caused by standard methods application. Phytoplankton pigment concentrations were retrieved from satellite and contact data using the method proposed, showing good correlation with biological data.
La Plata River Plume, challenging waters for atmospheric correction and TSM algorithms
Dogliotti, Ana I.; Vanhellemont, Quinten; Ruddick, Kevin
The La Plata River drains the second largest basin of South America, covering an area of 3.1 x 106 km2 and discharging an average of 23,000 m3 s-1 of freshwater into the Atlantic Ocean at 35ºS. The river outflow introduces suspended matter (with a suspended sediment concentration
ranging from 100 mg L-1 to 300 mg L-1), dissolved and particulate organic matter into the shelf influencing the optical properties of the coastal waters, making satellite sensors the most suitable tools available to map the river influence on the adjacent ocean. A data base of MODIS/Aqua level 2 total suspended matter (TSM) product (Nechad et al., Rem. Sens. Env. 2010) from the study region has been generated and the analysis showed that most of the upper region of the estuary is usually masked (CLD,HILT,ATMFAIL) due to the highly turbid and reflective waters. Thus, the application of a different atmospheric correction and adaptation of the TSM algorithm are required if useful information from this region is to be retrieved. Similar products from MERIS instrument are desired given its particular characteristics (more bands and higher spatial resolution) which make it suitable for retrieving information on water constituents in this highly turbid coastal region.
Ocean colour observation systems for harmful algal blooms in the southern Benguela
The Benguela, one of the most productive upwelling systems in the global ocean, suffers from the requent occurrence of a variety of harmful algal blooms (HABs). Harmful impacts of HABs are associated with toxicity and the high biomass which can lead to hypoxic events and, in extreme cases, the production of hydrogen sulphide. This frequently leads to extensive mortalities of marine organisms.Ocean colour remote sensing has demonstrated considerable potential for the observation of HABs, particularly so in the Benguela where the very high biomass bloom events typical of the system provide a strong optical signal.
The use of ocean colour provides the ability to observe HABs in near real-time and gives a greater understanding of the variability of HABs as ecologically prominent phenomena. This is achieved through using both standard MERIS and MODIS products, and emerging generic and system-specific analytical and empirical algorithms for both biomass and algal assemblage determination. These include: an analytical reflectance inversion algorithm, allowing estimates of chlorophyll at high biomass and descriptors of algal size; regional empirical algorithms based on red wavelengths; fluorescence line height and quantum yield products.
The performance of these algorithm is evaluated using the in situ database collected from 2003 - 2008 to assess their potential for both research and operational monitoring through CoastColour. A further key aspect of the project is the use of the database to validate the water-leaving reflectance and evaluate the suitability of various atmospheric correction procedures.
A research strategy for the Benguela places it as the primary site for bio-optical, phytoplankton physiology and photophysiology research in southern Africa. The development of in situ capacity through e.g., the deployment of moored research buoys, and the processing and dissemination of products to a large user groups via the Marine Remote Sensing Unit (MRSU) ensures that the southern Benguela will remain a core research center for ocean colour and bio-optical research in the near future.