On the Contents of Condensation Nuclei and Uncharged Nuclei on the Pacific Ocean and the Japan Sea

[摘要] Continuous measurements of the concentration of condensation nuclei and uncharged nuclei were made from August 2 to 9, 1948 on board the observation boat cruising about point (153°OO'E, 39°OO'N) on the Pacific Ocean. Observation was made with an improved Aitken nucleus counter with an electrical condenser. Observations of a similar kind were also made at the seaside of the Rebun Island (141°OO'E, 45°21'N) on the Japan Sea from May 5 to 12, 1948.The results are briefly compiled as follows:(1) The average content of nuclei is shown in the table.The value obtained on the Pacific Ocean, on an average, shows the smallest value ever obtained on the oceans. Such small content seems to imply that the nucleus content in pure maritime air is mainly affected by the life history of the air. The longer the air remains on the ocean the fewer the nucleus content in pure maritime air may become.(2) The diurnal change of the nuclei content was not found in the air on the Pacific Ocean. On the contrary, some diurnal changes, i. e. contents inc_??_easing in midday, were observed at the sea-side of the Japan Sea. It seems that the change occurs on a clear day, but it is not clear whether this change is caused by the new formation of nuclei at the ses-side or by the mixing of dusty inland-air with the sea-air carried by the sea winds.(3) A sudden decrease of nucleus content was observed on the Pacific Ocean. This change seemed to indicate a line of discontinuity in the maritime air mass passed by. Corresponding to this change of nucleus content, vapour pressure of the air also shows a slight increase, the change being more sluggish than that of nucleus content.It is interesting to note that the boundary layer with respect to vapour content is thicker than that with respect to nucleus content.(4) The ratio of charged nuclei of plus or minus sign to uncharged nuclei (N/N±) was 1.9 (aver. of 39 obs.) on the Pacific Ccean and 1.5 (aver. of 108 obs.) on the Japan Sea. The ratio shows a diurnal change, decreasing in midday (by the local time at 135E), both on the Pacific Ocean and Japan Sea. It is interesting that the time of occurrence of the change coincides with that which was observed by Torreson at Washington D. C., in both cases decreasing between about 0 and 10h (G. M. T.) after reducing the time of both observations to Greenwich mean tiem.(5) No changes in nucleus content were observed which were caused by the change of wind velocity in all the cases of observation. Assuming various vertical distributions of nucleus content and various values of “Austausch” coefficients, it was calculated that the nuclei formed at the surface of the sea water should be less then 10 per cm2/see on the case of the Pacific Ocean. Thus it was concluded that the ocean should not be said to be a main producer of nuclei under the conditions that the wind velocity observed on a ship was less than about 10m/s. (September 1949)

[学科分类] 大气科学