Ground based in situ observations of smps at Jungfraujoch (CH0001G). These measurements are gathered as a part of the following projects ACTRIS, CREATE, EMEP, GAW-WDCA and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: particle_number_size_distribution in aerosol (number_concentration_of_positive_ions_in_dry_aerosol_particles_in_air), particle_number_size_distribution in aerosol (number_concentration_of_positive_ions_in_dry_aerosol_particles_in_air), particle_number_size_distribution in aerosol (number_concentration_of_positive_ions_in_dry_aerosol_particles_in_air)