CoastColour Round Robin datasets: A data base to evaluate the performance of algorithms for the retrieval of water quality parameters in coastal waters

The use of in situ measurements is essential in the validation and evaluation of the algorithms that provide coastal water quality data products from ocean colour satellite remote sensing. Over the past decade, various types of ocean colour algorithms have been developed to deal with the optical complexity of coastal waters. Yet there is a lack of a comprehensive intercomparison due to the availability of quality checked in situ databases. The CoastColour Round Robin (CCRR) project, funded by the European Space Agency (ESA), was designed to bring together three reference data sets using these to test algorithms and to assess their accuracy for retrieving water quality parameters. This paper provides a detailed description of these reference data sets, which include the Medium Resolution Imaging Spectrometer (MERIS) level 2 match-ups, in situ reflectance measurements, and synthetic data generated by a radiative transfer model (HydroLight). These data sets, representing mainly coastal waters, are available from doi:10.1594/PANGAEA.841950. The data sets mainly consist of 6484 marine reflectance (either multispectral or hyperspectral) associated with various geometrical (sensor viewing and solar angles) and sky conditions and water constituents: total suspended matter (TSM) and chlorophyll a (CHL) concentrations, and the absorption of coloured dissolved organic matter (CDOM). Inherent optical properties are also provided in the simulated data sets (5000 simulations) and from 3054 match-up locations. The distributions of reflectance at selected MERIS bands and band ratios, CHL and TSM as a function of reflectance, from the three data sets are compared. Match-up and in situ sites where deviations occur are identified. The distributions of the three reflectance data sets are also compared to the simulated and in situ reflectances used previously by the International Ocean Colour Coordinating Group (IOCCG, 2006) for algorithm testing, showing a clear extension of the CCRR data which covers more turbid waters.JRC.H.1-Water Resource

Measurements of CDOM absorption spectra using different Instruments and techniques: A round robin exercise and extensive field data set.

The optical measurement of Chromophoric Dissolved Organic Matter (CDOM) throughout the open-ocean and coastal regions has played a crucial role in the development of Ocean Color algorithms. However many spectrophotometric instruments equipped with 10cm cells are not sensitive enough to measure light attenuation from CDOM in open ocean or case 1 waters. One solution is to significantly increase the optical path length, which gives the photons of light a greater probability of being absorbed before reaching the detector. Liquid waveguide capillary cells (LWCC), integrating cavity absorption meters (ICAM), and Wetlabs absorption attenuation meters have all become prominent instruments in the community for making long path length measurements. However limitations arise due to the loss of light from scattering, spectral offsets caused by temp and salinity offsets, and cell contamination with subsequent micro-bubble formation. An extensive round robin comparison was carried out with versions of all these instruments at NASA Goddard Space Flight Center in the fall of 2013. It was part of an ongoing CDOM workshop with an international committee. Many new insights pertaining to the methodology and results of the measurements will be presented along with an extensive field data set of LWCC measurements.JRC.H.1-Water Resource