Ground based in situ observations of nitric_acid at Karasjok (NO0055R) using filter_1pack. These measurements are gathered as a part of the following projects AMAP, NILU, EMEP and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: nitric_acid in air (mass_concentration_of_nitric_acid_expressed_as_nitrogen_in_air)