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Cloud Condensation Nuclei over the Springtime Arctic |
Desert Research Institute
hudson@dri.edu
More than 23 hours of continuous CN and 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 8 flights during May, 1998 over the mostly frozen Arctic Ocean at least 500 km north of the Alaska 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 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.
