Physical Characteristics of Arctic Stratus Clouds

Observations of the physical properties of Arctic status clouds (ASC) over the Beaufort Sea area were made by the NCAR Electra aircraft during June 1980. The cloud morphology and microstructure observed during these experiments are described here. Arctic stratus clouds were formed under various meteorological conditions, but not when the axis of the Beaufort Sea ridge was zonal and the airflow into the region was continental. The mean drop diameter in clouds observed under all conditions remained near 10 μm, while the mean liquid water content (LWC) was characteristic of the air mass forming the clouds and essentially determined by the mean drop concentration. Clouds showed considerable horizontal homogeneity but significant vertical changes occurred within them. The vertical profiles of LWC show that the values generally increased with height, as a result of an increase in droplet size rather than concentration. The drop size distribution near the base was monomodal, characteristic of condensation on a nucleus spectrum, but changed to a bimodal distribution near the top of the cloud.