Ground based in situ observations of particle_number_concentration at Zeppelin mountain (Ny-Ålesund) (NO0042G) using cpc. These measurements are gathered as a part of the following projects NILU, EMEP, GAW-WDCA, EUSAAR and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: particle_number_concentration in aerosol (number_concentration_of_particles_in_dry_aerosol_particles_in_air)