Multi-sensor satellite time series of optical properties and chlorophyll-a concentration in the Adriatic Sea

• Published in: Progress in oceanography Vol. 91; no. 3; pp. 229 - 244
• Main Authors: Mélin, F, Vantrepotte, V, Clerici, M, D’Alimonte, D, Zibordi, G, Berthon, J.-F, Canuti, E
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2011
• Subjects: Adriatic Sea; Algorithms; chlorophyll; Marine; moderate resolution imaging spectroradiometer; Oceanography; Optical properties; Radiance; Remote sensing; Satellites; Time series; time series analysis; Adriatic Sea
• ISSN: 0079-6611; 1873-4472
• DOI: 10.1016/j.pocean.2010.12.001

Advanced remote sensing techniques and regional algorithms are combined to produce and analyze a 12-year multi-sensor time series of bio-optical properties for the Adriatic Sea. First, a multi-sensor series of normalized water-leaving radiance LWN is created with an optically-based merging technique applied to SeaWiFS and MODIS data, then distributions of inherent optical properties (IOPs) are obtained with a semi-analytical bio-optical model. Additionally, Chla is computed by two regional empirical algorithms associated with two classes of optical properties representative of open ocean waters and Adriatic coastal regions (Classes 1 and 2, respectively). The domain of applicability of each algorithm is dynamically determined on the basis of the LWN input spectrum by a novelty detection approach. The various satellite products are validated using a comprehensive bio-optical time series collected in the northern Adriatic. At the basin level, the frequency of occurrence of Classes 1 and 2 are 61% and 10%, respectively, with Class 2 waters particularly located in the northern part and characterized by higher levels of Chla and IOPs. The annual cycle of Chla over the 12-year period exhibits significant variations in amplitude and phase; moreover, the annual cycle shows a reduced amplitude during a period centered on 2004 for a time interval that varies with the region. In the northern Adriatic, the overall level of Chla appears lower between 2003 and 2008 compared to the beginning of the series.