Annual geometric mean of Chlorophyll-a in the Baltic Sea (Envisat MERIS) 2003-2011/Yearly geometric mean of Chlorophyll-a in the Baltic Sea (Envisat MERIS) 2003-2011

**[FI]** satellite observations are used for monitoring chlorophyll a (ug/l) in surface water in the Baltic Sea during molten water from June to October. Chlorophyll A (chl-a) describes the amount of algae in water, but not directly the number of cyanobacteria. It is also a key factor in assessing the level of eutrophication of water. The data represents the annual level of chlorophyll a during the summer, covering all cloudless observations from the beginning of June to the end of September. The seasonal composite data are calculated using the geometric mean of all observations for each pixel, which represents statistically well the distribution of the data.The material has a terrain separation capacity of 300 m. The A-chlorophyll aggregate data was calculated in SYKE for the years 2003-2011 using the 3 rd Reprocessing data of Envisat MERIS (Medium Resolution Imaging Spectrometer). Satellite observations have been processed to concentrations of a chlorophyll using the FUB (Freie University of Berlin) (Shcroeder et al., 2007). Seasonal composites represent for each year the concentrations of chlorophyll-a in the period from 1 June to 30 September. This period is used for HELCOM’s A-Chlorophyll Status Assessments and for EU Directive Reporting for High Seas (Marine Strategy Directive). Purpose: Assessment and eutrophication of water status in the Baltic Sea. The material is part of SYKE’s open data (CC BY 4.0). *** **[En]** Satellite remote sensing is used to monitor the Chlorophyll-a (ug/l) of surface water in the Baltic Sea during the open water season from April to October. Chlorophyll-a (chl-a) represents the quantity of algae in the water but not directly the amount of cyanobacterium. The dataset describes the annual level on summerly chl-a and all non-cloudy daily images have been accounted from the period of June-September. The dataset have been calculated using geometric mean of all observations for each pixel. The spatial resolution is 300 meters. A Chlorophyll-a dataset for years 2003-2011 have been calculated in the Finnish Environment Institute (SYKE) using Envisat MERIS (Medium Resolution Imaging Spectrometer) 3 rd Reprocessing data. Satellite data have been processed to chl-a concentrations using FUB (Freie University of Berlin) processor. The season composites describe the level of all available daily non-cloudy Chlorophyll-a observations for the period of 1.6.-30.9. of each year. The period used for the aggregate of summerly observations follows the status assessment periods accounted in HELCOM chl-a status assessment and the directive reporting (Marine Strategy Diretive). Purpose of use: Status assessment and monitoring eutrophication of the water in the Baltic Sea. *** ## References/Reference: 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. Attila, J., Kauppila, P., Alasalmi, H., Kallio, K., Keto, V., Bruun, E., & Koponen, S. (2018). Applicability of Earth Observation Chlorophyll-a data in assessment of water status via MERIS — with implications for the use of OLCI sensors. Remote Sensing of Environment, 212, 273-287. https://doi.org/10.1016/j.rse.2018.02.043 Attila J. (2019). Water quality monitoring and assessment of the Northern Baltic Sea using Earth Observation. Aalto University publication series, 229/2019. 178p. ISBN (pdf) 978-952-60-8867-9, ISSN (pdf) 1799-4942, http://urn.fi/URN:ISBN:978-952-60-8867-9. HELCOM (2015). Eutrophication Assessment Manual, Annex 3A. http://www.helcom.fi/helcom-atwork/projects/eutro-oper/. Last revision 2015. HELCOM (2018): State of the Baltic Sea — Second HELCOM Holistic assessment 2011-2016. Baltic Sea Environment Proceedings 155, 155p. *** **WMS server/WMS service endpoint**: https://geoserver2.ymparisto.fi/geoserver/eo/wms **WMS level/WMS layer**: MER_FSG_CHLA_geomean_yearly_assper_[YEAR] *** **[EN]** The compositions are calculated from all observations of the MERIS instrument of the Envisat satellite Envisat in the summer season. *** **[En]** Composites have been calculated from all observations of the Envisat satellite’s MERIS instrument for the summer season.