Ground based in situ observations of filter_absorption_photometer at Alert (CA0420G). These measurements are gathered as a part of the following projects GAW-WDCA and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: equivalent_black_carbon in aerosol (mass_concentration_of_equivalent_black_carbon_in_dry_aerosol_particles_in _air), flow_rate in aerosol