Abstract
Observation of cloud condensation nuclei was carried out at Syowa Station (69°00'S, 39°35'E), Antarctica from the beginning of February to the end of December, 1968 using a chemical diffusion chamber. Supersaturation adopted were in five grades of 0, 0.05, 0.1, 0.5 and 1% at the same time. As a result the mean number concentrations of 0 and 1% supersaturations at the station were 3×102 and 8×102 particles per cm3, respectively. The maximum concentrations of 0 and 1% were 3×103 and 4×103, and in only one case 9×103 particles per cm3 at 1% was seen. The minimum concentrations of both supersaturations were nil, but in general they were approximately in an order of 1×102 particles at 1% supersaturation. The high concentrations were observed in the range of the wind direction from ESE to S and they were related to the wind direction rather than wind velocity. The spectra of the number concentration in the range from 0 to 1% supersaturations showed two distinct patterns. One showed nearly flat spectra, namely 2-3×103 and the other showed steep gradients of 1-5×102 and 2-4×103 particles per cm3 at 0 and 1% supersaturations, respectively. The nuclei spectra showing steep gradients were considered to be from a man-made source judging from the shapes of the spectra and by the wind directions at the station. The nuclei showing a flat pattern were surmized to be of an oceanic source. An examination of the washout effect of cloud condensation nuclei in "before", "during" and "after" solid precipitation was carried out. As a result, the value of the number concentration of cloud condensation nuclei in "during" precipitation was less approximately 30% than that of "before" precipitation, and the value of the concentration in "after" precipitation was greater 200% than that of "during" precipitation in both 0 and 1% supersaturations.
