Particle size spectra of Arctic-derived air masses were investigated during late winter and spring 1983 from Ester Dome Observatory in central Alaska. Most of the particle size distributions were bimodal with accumulation modes (geometric mean diameter 0.2 &mgr;m) and nucleation modes (geometric mean diameter <0.015 &mgr;m). Virtually all mass (0.5-5 &mgr; g m-3) and a third to half the number of particles detected with condensation nucleus counters were in the large accumulation mode. The presence of the nucleation mode suggests that gas-to-particle conversion is taking place in cold, dark subpolar atmospheres at mass conversion rates of ~10-21 g cm-3 s-1. |