Vertical distributions of cloud condensation nuclei spectra over the springtime Arctic Ocean

More than 23 hours of continuous condensation nuclei (CN) and cloud condensation nuclei (CCN) spectral data from the Arctic Clouds Experiment are presented and analyzed. These measurements were made at altitudes ranging from 6 km to 30 m in eight flights during May 1998 over the mostly frozen Arctic Ocean at least 500 km north of the Alaskan coast. Concentrations generally increased with altitude with a pronounced deficit in the boundary layer when low stratus clouds were present. The low-level vertical gradient could be demonstrated to be a result of cloud scavenging. Boundary layer concentrations at 0.8% supersaturation averaged 76 cm^-3 with low cloud (below the low cloud) and 250 cm^-3 when no low cloud was present. The ratio of CCN to CN (total particles) was relatively high, usually exceeding 0.6. The relatively high concentrations at higher altitudes, the high CCN/CN ratio, and the lower CCN spectral slopes are characteristic of an aged aerosol probably due to long-range transport.