Annual Baltic Sea algae (Envisat MERIS) 2003-2011/Yearly algae composites of the Baltic Sea (Envisat MERIS) 2003-2011

**[En]** The annual compendium of surface algae observations in the Baltic Sea area is combined with daily surface algae observations of the summer season, 2003-2011. Daily surface algae observations are interpreted into four categories that describe the likelihood of surface algae occurring in a given area. The categories on the map are 1) non-surface algae, 2) possible, 3) probable, and 4) secure surface algae. The annual compilation gathers the surface algae observations of the main basin of the Baltic Sea, the Bothnian Sea and the Gulf of Finland from June to August. The aggregates have a terrain separation capacity of 500 m. Surface observations are based on the amount of a-chlorophyll and turbidity. The data have been calculated using the Envisat MERIS (Medium Resolution Imaging Spectrometer) instrument 3 rd Reprocessing. A-chlorophyll concentration has been interpreted using the Freie University of Berlin (FUB) model based on neural network computing (Shcroeder et al., 2007). Opacity is interpreted by a model based on the C2R (Case-2 Regional) network (Brockmann et al. 2016; Doerffer et al. 2007; 2008a; 2008b). Purpose of the material: Monitoring of water quality in the Baltic Sea, Algae Information. The data is part of SYKE’s open datasets (CC BY 4.0). *** The annual Baltic Sea offshore algae composite is a combination of all surface floating algae bloom observations in the summerly cyanobacteria bloom period. The data covers Baltic Sea offshore areas. Surface algae bloom data is produced using a four-class interpretation map that describes the probability of the occurrence of surface algae blooms. Algae classes are: 1) no, 2) potential, 3) likely, and 4) evident surface algae. Annual composites describe the extent of surface algae blooms during June-August. The composites from years 2003-2011 are made with a ground resolution of 500 m. Surface algal observations are based on the amount of Chlorophyll-a and turbidity using the 3 rd Reprocessing Data of the Envisat MERIS (Medium Resolution Imaging Spectrometer) instrument. CHL-a was modelled using the FUB model based on neural network computation (Freie University of Berlin) (Shcroeder et al., 2007). The turbidity estimation is based on a C2R neural network model (Case-2 Regional), (Brockmann et al. 2016; Doerffer, et al. 2007; 2008a; 2008b). Purpose of use: Monitoring of water quality in the Baltic Sea, algae bloom reviews. *** ## References/References [Anttila, S., Fleming-Lehtinen, V., Attila, J., Junttila S., Alasalmi, H., Hällfors, H., Kervinen, M., Koponen, S., (2018). A novel cyanobacterial surface accumulation indicator for the Baltic Sea. A novel earth observation based on ecological indicator for cyanobacterial blooms. International Journal of Applied Earth Observation and Geoinformation 64:145-155. DOI: 10.1016/j.jag.2017.09.007. Available online (Oct/2017) (http://www.sciencedirect.com/science/article/pii/S0303243417301964) Schroeder, T., Schaale, M., & Fischer, J. (2007). Retrieval of atmospheric and oceanic properties from MERIS measurements: A new Case-2 water processor for BEAM. International Journal of Remote Sensing, 28(24), 5627-5632. Brockmann, C & Doerffer, R. (2016). Evolution of the C2RCC neural network for Sentinel 2 and 3 for the retrieval of ocean colour products in normal and extreme optically complex waters. The PROC. Living Planet Symposium, ESA SP-470. Doerffer, R. & Schiller, H. (2007). The MERIS Case 2 algorithm. International Journal of Remote Sensing, 28 (3-4), 517-535. doi:10.1080/01431160600821127. [Doerffer, R., & Schiller, H. (2008a). Seas Regional Coastal and Lake Case 2 Water Project Atmospheric Correction ATBD (Algorithm Theoretical Basis Document) 1.0. 41 p. pdf](https://www.semanticscholar.org/paper/Algorithm-Theoretical-Basis-Document-(ATBD)-MERIS-2-Doerffer-Schiller/c584b7288212983adcd32488bfc802d7f01016d#paper-header) Doerffer, R. & Schiller, H., (2008b).Meris Lake Water Project — Lake Water Algorithm for BEAM, ATBD (Algorithm Theoretical Basis Document) 1.0, 17 p. *** **WMS server/WMS service endpoint**: https://geoserver2.ymparisto.fi/geoserver/eo/wms **WMS level/WMS layer**: EO_MERIS_ALGAE_v1_season_composite_[YEAR] *** **[En]** The compositions have been calculated from the surface algae observations of the summer season Envisat MERIS. *** **[En]** Composites have been calculated from surface algae observations of the Envisat MERIS for the summer season.