抄録
In the Central Meteorological Observatory of Japan in Tokyo (φ35° 41' N, λ139° 46' E) the registration of direct solar radiation had been in the regular program of observations in the interval between January 1930 and April 1932. In the present report, the variation of the dust content of the atmosphere in the middle part of Tokyo is studied statistically using the method given by A. Ångström (Geografiska Annaler Bd. 12, s. 130, 1930).
The maximum and minimum values of monthly means of the amount of dust content β were occurred in July and February respectively. As for the diurnal variation no conspicuous change was perceived, although in the morning of summer months the dust content were larger than those of the afternoon. In the morning of winter months, on the contrary, the values of β were smaller than those of afternoon. It is worth to be remarked that the dust content, in general, varies with the velocity and direction of wind, and the relation seems to be especially prominent in the case of northerly wind with velocity of more than 5m/sec.
