Monthly mean concentration of chlorophyll a on the sea surface of the Baltic Sea

Monthly mean surface concentration of chlorophyll a in the years 2003-2022 calculated on the basis of data from the SatBaltic System (https://satbaltyk.iopan.gda.pl/). Maps of monthly average values with a resolution of 1 km were derived from daily satellite data from the Moderate Resolution Imaging Spectroradiometer (MODIS). Gaps in satellite images caused by the presence of clouds were filled using the results of a numerical ecohydrodynamic model. Average concentration of chlorophyll a in March 2021 in the surface layer of the Baltic Sea