Running 6-year analysis of Water body chlorophyll-a in the Baltic Sea. Four seasons (March-May, June-August, September-November, December-February). Every year of the time dimension corresponds to a 6-year centred average. Periods span between 1974-2021. Analyses for depths (m) (HELCOM standard depths): 0, 5, 10, 15, 20, 30.

Data Sources: observational data from SeaDataNet/EMODnet Chemistry Data Network. 
Description of DIVA analysis: Geostatistical data analysis by DIVAnd (Data-Interpolating Variational Analysis in n dimensions) tool. 
GEBCO_08 Grid (30 arc-seconds) topography is used for the contouring preparation. 
Files contain analysed fields, error fields and combined field with the deepest value for each grid point selected. 
Also pre-masked fields using relative error threshold 0.3 and 0.5 are included. 
In the analyses the horizontal correlation length is fixed to 80 km and decreasing towards the coastline, 
the vertical correlation length is varying with depth.
Signal to noise ratio is fixed to 1.0. 
Background fields were created using data for the given time period and season. 
Log transformation was used in the analyses. No detrending, advection constraints or weighting are applied. 
Unit is mg/m3.