The author studied the relation between diurnal variation of cloud amount in Japan and various meteorological elements, such as, daily mean humidity, daily mean lapse rate of lower atmosphere, daily mean wind speed, daily most frequent wind direction, and daily change of pressure. Thus he found the following types. a) After passage of a trough and when the air is dry:- one maximum of cloud amount in the afternoon. b) After passage of a trough:- main maximum in evening and secondary maximums at just before noon and midnight, and distinct minimum in early morning. c) When wind force is very weak:- similar as above, but a very sharp maximum at midnight. d) Northerly or northeasterly winds:- two maximums in morning and afternoon. e) Southerly or southeasterly:- maximum in morning and minimum in evening, hence a typical morning overcast occurs. f) Low approaching:- similar as above, but one maximum before noon and minimum in night time. g) Wind force strong:- four maximums at about 6h, 12h, 18h and 24h, hence cloud amount is variable. h) Stratus or fogs:- minimum in day time and maximum at night.
In this paper absorption coefficient of water vapour in the near infra-red region between, 1.2 μ and 3.5 μ was calculated by the same method which was employed by us in calculating absorption coefficient of water vapour in the far infra-red region beyond 5 μ. (G. Yamamoto & G. Onishi, Sei. Reports Tohoku Univ. Ser. 5, 1, p. 5 (1949)). In the near infra-red region there are three absorption bands, i. e., 1.4 μ band, 1.8 μ band and the strongest 2.7 μ band which is extending between 2.5 μ and 3.5 μ. For each band the generalized absorption coefficients of Elsasser were calculated basing on the analysed data of Nielsen. The result of calculation was compared with the measurement of Hettner. The comparison shows that in each band Hettner's values are greater than our calculated values and the former values are extending broader to the margin of each band than the latter values. But it must be remembered that Hettner's measurements were carried out on water vapour of 1 atmospheric pressure and 400°A, so that under the temperature of our calculation Hettner's values must be reduced to about 1/4 of their original values. Then it will be said concludingly that both Hettner's measurement and our calculation nearly agree in magnitude in the central part of each band and that measured bands by Hettner are far broader than our calculation. The detailed description in English of this investigation will be published on Sci. Rep, of Tôhoku Univ. Ser. 5 Vol. 2 soon.
The vertical distribution of water vapour can be considered to consist of two factors, the one concerning with the distribution of saturated vapour pressure and the other, with that of humidity or degree of nonsaturation. The former can be calculated theoretically if the vertical distribution of temperature is given, but the latter cannot be calculated theoretically at present. If we assume that humidity decreases exponentially with height, admitting some error, we have for the vertical distribution of e in the polytropic atmosphere, where γ is the lapse rate in degree/km, T_??_ surface air temperature in absolute degree, z height in km. The values of e calculated by the formula agree with the observed values of e at Sendai and Hukuoka within the errors of 12% up to 6km high.
The auto-correlation coefficient for the purely random sequence was already studied by G. U. Yule and S. Moriguti, but by auto-correlation coefficient for the difference stationary time series is scarcely studied. The author treats them statistically, inducing the correlation coefficient, and investigates their property for some special cases. The auto-correlation coefficient of the 1st difference is given by in general, the auto-correlation coefficient of the r-th difference is given by where (2r/r-τ-p)=2rCτ-p-p (equals to combination). For random sequence, we have the following relations. and finally, we referred to the relation for the sinusoidal limit theorem we obtained the following result. The necessary and sufficient conditions that the difference stationary time series is to be a simple Markoff process are that the difference sequence is a singular stationary process.
In Winter the dust storms occur frequently at Honjo and they disturb the electric field of the atmosphere. At the Honjo Observatory the Bendorf's Electrometer has been set since November 1948, and we obtained many interesting records of dust storms. From November 1948 to April 1949 we observed the dust storms 7 times, and two of them caused the variation of positive potential gradient and others negative. The maximum departures of the potential gradient were 3500 V/m and -2600V/m. When the dust storms do not occur at the station and they occur at distant places or we can find them nowhere, the electrometer records the disturbance of the potential gradient in windy days. Its characteristics resemble the variation caused by the dust storms. We also observed the space charge of the atmosphere. The instrument is wire-netting cube and at the centre of this cube polonium collector is supported. The collector is connected to the leaf electrometer. When the potential gradient is positive (or negative) at the dust storms, the space charge is also positive (or negative). The value. of the space charge in the dust storms is 8 times as large as that of the calm days. We made further an experiment on the charge of the dust particles. We used three kinds of sand or soil. The result of the experiment shows that the larger particles have positive charge and smaller particles have negative charge by the friction between dust particles.