Observations of Cloud Condensation Nuclei, Sodium-Containing Particles, Ice Nuclei and the Light-Scattering Coefficient Near Barrow, Alaska

Abstract

Measurements of the concentrations of cloud condensation nuclei (CCN), sodium-containing particles (SCP) and ice nuclei (IN), and the aerosol light-scattering coefficient were made near Barrow, Alaska, from 8?28 March 1970. The average concentrations of CCN (at 1% supersaturation) and SCP (in the size range 0.06 to 1.0 ?m) were 90 and 0.2 cm?2, respectively, The average concentration of IN at ?20°C, measured with an NCAR counter without correcting for internal losses, was 0.15 l?1. The light-scattering coefficient was generally on the order of 5 ? 10?5 m?1. Although the SCP concentrations were less than 1% of the CCN concentrations at 1% supersaturation, extrapolation of the CCN spectra down to supersaturations which exist in fogs and stratus indicate that in these situations the SCP probably comprise the majority of the activated CCN. The SCP were probably airborne sea-salt particles; their concentrations increased when open leads, which exposed sea water, were present near the measuring site. Under stable meteorological conditions, the CCN appeared to be transported over large distances (400 km). Despite the comparative remoteness of the site, the measurements indicate that anthropogenic aerosols were present.