On the Size Distribution of Submicron Aerosols in the North Pacific Air

Ito Tomoyuki

doi:10.2151/jmsj1965.58.1_81

The size distributions of Submicron aerosols were measured at Minamitorishima Is. (Marcus Is., 24°N, 154°E) and the Ogasawara islands (Bonin Is., 27°N, 142°E) during two weeks in the autumns of 1975 and 1976 respectively. The purpose of these measurements was to get information about the concentrations and size distributions of aerosols in the North Pacific maritime atmosphere.<br>To get the continuous records of the size distribution of natural aerosols, we employed the diffusion decay technique and an improved Pollak type condensation nucleus counter. From the set of decay rates of concentration of aerosols passing through the diffusion batteries, the size distribution of aerosol particles with radii between 0.002 and 0.2μm was determined by use of a response matrix method.<br>The most important finding in the present work is that there is a notable difference in the size distributions and total concentrations of aerosols depending upon the origin of the air mass. In an air mass which has come from the main island of Japan, the total number concentration of aerosols is of the order of 1, 000 to 2, 000cm-3 and their size distribution tends to have a narrow range with a main peak between 0.02 and 0.07μm in radius. On the other hand in an air mass of mid-latitude maritime origin, the total number concentration of aerosols is of the order of 250cm-3, which is comparable to the background concentra- tion in these oceanic regions. The size distribution of aerosols in such an air mass tends to have a rather broad range with a main peak at around 0.02μm and a second peak, though not always detected, at around 0.004μm in radius.<br>Present results suggest the possibility of the aerosols transported from land affecting the background concentration of the cloud condensation nuclei in the clean oceanic atmosphere.

On the Size Distribution of Submicron Aerosols in the North Pacific Air

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