Barrow surface aerosol: 1976–1986

Abstract

Measurements at Barrow during the first Arctic Gas and Aerosol Sampling Program (AGASP-I), conducted in March–April 1983, showed a series of aerosol events detected at the ground that coincided with rapid long-range transport paths from Eurasia to the vicinity of Barrow. These events were strongly correlated with aerosol loading in the vertical column (optical depth). Aerosol and meteorological measurements at Barrow during the second AGASP (AGASP-II), conducted in April 1986, indicate no rapid long-range transport from lower-latitude source regions to the vicinity of Barrow, and only limited vertical transport from above the boundary layer to the surface. Aerosol size distribution measurements in the 0.005–0.1 μm diameter size range using a Nuclepore-filter diffusion battery apparatus showed a median diameter of about 0.01 μm during times of high condensation nucleus (CN) concentrations and 0.05 μm during low concentrations. Aerosol black carbon concentrations exceeding 200 ng m −3 were detected at the surface and were more strongly correlated with CN concentrations than with aerosol scattering extinction ( σ sp ), suggesting that aerosol carbon was generally associated with small particles rather than large particles. A continuous record of CN and σ sp measurements is available from 1976 to the present. The σ sp data show a strong annual cycle, having a maximum exceeding 10 −5 m −1 in the winter and spring (the Arctic haze), and a minimum of about 10 −6m −1 in the summer and fall. The CN data show a semiannual cycle, having a maximum of several hundred per cubic centimeter coinciding with the maximum in σ sp in early spring, and a secondary maximum in August. Minima in CN concentration of about 100 cm −3 occur in summer and late fall. No significant diurnal cycle appears in either the CN or σ sp long-term records.