Monthly satellite data (SeaWiFS, MODIS, MERIS, VIIRS) over a 21-year period (1998-2018; from the Globcolour project; http://globcolour.org) are used to calculate the Photosynthetically Available Radiation (PAR) reaching the seafloor in the coastal zone (0 to 200 m depth). Depths are from the 2019 General Bathymetric Chart of the Oceans (GEBCO; https://www.gebco.net) gridded bathymetry data (1/240 degree resolution). Longitude, latitude, depth and pixel area can be found in the NETCDF file CoastalLight_geo.nc. Optical parameters (PAR at surface, attenuation coefficient for PAR, and PAR on sea floor)can be found in the following NETCDF files:- Monthly climatologies, mean values: January (01) to December (12): CoastalLight_01.nc, CoastalLight_02.nc, ..., CoastalLight_12.nc- Monthly climatologies, minimum values: January (01) to December (12): CoastalLight_min_01.nc, CoastalLight_min_02.nc, ..., CoastalLight_min_12.nc- Monthly climatologies, maximum values: January (01) to December (12): CoastalLight_max_01.nc, CoastalLight_max_02.nc, ..., CoastalLight_max_12.nc- Monthly climatologies, standard deviation values: January (01) to December (12): CoastalLight_sd_01.nc, CoastalLight_sd_02.nc, ..., CoastalLight_sd_12.nc- Climatology over the whole 21 year period, mean values: CoastalLight_00.nc- Climatology over the whole 21 year period, minimum values: CoastalLight_min_00.nc- Climatology over the whole 21 year period, maximum values: CoastalLight_max_00.nc- Climatology over the whole 21 year period, standard deviation values: CoastalLight_sd_00.nc