North Sea Fronts

KLIWAS Climatology of Sea Surface Temperature and Ocean Colour Fronts in the North Sea. This is the first version (1.0) of a climatology for Sea Surface Temperature and Ocean Colour Fronts for the region: 47 to 63 °N, 16 °W to 15 °E (Standard-Grid AATSR, MERIS and MODIS) 48 to 63 °N, 11 °W to 17 °E (Standard-Grid AVHRR) It contains the multi-annual, multi-seasonal, and multi-monthly means of the gradient magnitude and of the gradient vector (magnitude and direction) for a frontal zone as well as the number of observations, the number of observations of frontal zone over a defined time interval and the probability of a front observation. The development of an algorithm which automatically detects frontal positions and gradients from satellite data was driven by the need to establish a climatology for oceanographic fronts in the North. GRADHIST is a new algorithm for the detection and mapping of oceanic fronts, which is based on a combination and refinement of the gradient algorithm of Canny (1986) and the histogram algorithm of Cayula and Cornillon (1992). GRADHIST preserves the main principles of both algorithms, improves the quality of front detection and can be applied to various ocean parameters as well as to different sensors. GRADHIST has been validated using both synthetic and real data and applied to sea surface temperature and ocean colour parameters retrieved from satellite data. After the algorithm has been validated and tested the satellite data have been processed to compute the gradient magnitude and gradient direction. Based on these two parameters the temporal statistic has been derived which include the calculation of a set of statistical measures for SST and Ocean Colour front products.