Ground based in situ observations of nephelometer at Sycamore Canyon (US9035R). These measurements are gathered as a part of the following projects GAW-WDCA, IMPROVE and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: aerosol_light_scattering_coefficient in aerosol (volume_scattering_coefficient_in_air_due_to_dried_aerosol_particles)