Ground based in situ observations of filter_1pack at Hurdal (NO0056R). These measurements are gathered as a part of the following projects NILU and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: nitrate in aerosol (mass_concentration_of_nitrate_expressed_as_nitrogen_in_dry_aerosol_particles_in _air), nitric_acid in air (mass_concentration_of_nitric_acid_expressed_as_nitrogen_in_air), sum_nitric_acid_and_nitrate in air+aerosol (mass_concentration_of_sum_nitric_acid_and_nitrate_expressed_as_nitrogen_in_aerosol)