Patterns in Water Quality Products of the North Sea: Variogram Analyses of Single and Compound Seawifs Chl & Spm Grids

In Europe, increasing political interest drives the investigation into the spatial aspects of water quality measurements. Additionally, unprecedented information on patterns in chlorophyll (CHL) and suspended particulate matter (SPM, also known as total suspended matter TSM) concentrations in coastal and marine ecosystems can be discerned from long-term hyperspectral data from ocean colour sensors. Variograms extracted from a dataset of 287 TSM and 287 CHL Sea-viewing Wide Field-of-view Sensor (SeaWiFS) products from September 1997 until December 2004 were analysed to characterise CHL and TSM patterns in the North Sea. In this paper, the spatial variability in optical characteristics of the North Sea is demonstrated by examples of CHL and TSM quicklooks and variograms for both individual images and seasonal composites, which were made to capture persistent patterns and overcome cloud cover. The range and the form of the variograms vary substantially per parameter (CHL or TSM) and per image. A seasonal differentiation in particularly TSM and to a lesser extent CHL can be identified from the variograms of the composites. This information should be incorporated in the assessment of in situ sampling schemes. * Corresponding author: [email protected]