Interpolated fields of satellite-derived multi-algorithm chlorophyll-a estimates at global and European scales in the frame of the European Copernicus-Marine Environment Monitoring Service

Abstract

ABSTRACT The new level-4 daily chlorophyll-a interpolated products described in this paper and freely available in the Copernicus-Marine Environment Service, aim at providing daily continuous fields (cloud-free) of satellite-derived chlorophyll-a surface concentration at two different resolutions: 4*4 km over the world and 1*1 km resolution over Europe. The multi-sensor daily analyses, by filling the cloudy pixels, provide high-frequency retrievals of chlorophyll-a which can contribute to a better monitoring of the phytoplankton biomass. From a methodological point of view our approach is a combination of a water-typed merge of chlorophyll-a estimates and an optimal interpolation based on the kriging method with regional anisotropic covariance models. These analysed products have been designed to meet the expectations of the end users, by considering both the typical lack of observations during cloudy conditions and the historical multiplicity of available algorithms involved by case 1 (oligotrophic) and case 2 (turbid) water classifications. These products gather MODIS (Moderate Resolution Imaging Spectroradiometer), MERIS (MEdium Resolution Imaging Spectrometer), SeaWiFS (Sea-viewing Wide Field-of-view Sensor), VIIRS (Visible Infrared Imaging Radiometer Suite) and OLCI (Ocean and Land Colour Instrument) daily observations from 1997 to the present. A total product uncertainty, i.e. a combination of the interpolation and the product error, is provided for each pixel.