Guneroglu, A, Kose, E, Karsli, F, Feyzioglu, M (2010). INTERCOMPARISON AND USAGE OF DIFFERENT Chl-a ALGORITHMS AND in-situ VALIDITATION OF OC3M IN CONTINENTAL SHELF WATERS OF THE BLACK SEA. FRESENIUS ENVIRONMENTAL BULLETIN, 19(3), 452-460.
Currently several operational ocean color algorithms are used for ocean monitoring purposes. This study evaluated inter-comparison of three different sensor Chl-a retrival algorithms which are Meris Algal1 and Algal2, SeaWiFS (OC4V4) and Modis-Aqua (OC3M) for their potential usage in eutrophication monitoring in continental shelf of Southern Black Sea as well as in situ validitation of Modis-Aqua (OC3M). Clear sky multispectral images of three sensors obtained for the same day and time of the year, classified and processed to retrieve Chl-a values for both open and coastal areas. Standard operational algorithms are used during the satellite data processing. The results reveal that a high level of correlation in the retrieved and log-transformed Chl-a data among all sensors which is between 0.88-0.94 for open areas and 0.77-0.94 for coastal areas. The highest correlation was found between OC4V4 and OC3M in coastal and open waters. In situ validitation of OC3M in coastal waters of the Black Sea revealed the lowest bias (25%) for summer-fall season and the highest bias (72%) for spring season data. In situ Chl-a value is overestimated by a factor of 2.6 when taking average of all data sets. Eventhough standard operational data from SeaWiFS, Modis-Aqua and Meris can be used for eutrophication monitoring purposes in Black Sea, an urgent need for regional algorithms arises.