Typhoon of summer can be considered in good approximation to move by the general current, hence the path of typhoon will be predicted by removing the cyclonic current due to typhoon itself from the actual field of air current. Assuming that the velocity distribution in typhoon is given by the field of general current was constructed numerically from the observation of upper air current for some actual examples, and the suggestion was confirmed.
Synoptic charts are classified according to the path of typhoon and it was investigated whether the path of typhoon is affected by rainfall or not. It was found that the typhoon travels on rainy region which is explained by the frontal zone betweep Ogasawara and Siberian air-masses.
This paper describes the results of wind-tan-nel test and smoke test which were made to study the relation between snow-fence and snow-drift. It is found that the position and amount of snow-drift are closely related to the change of streamlines of wind due to the setting of snow-fence.
H. v. Helmholtz introduced an important idea of air-mass ring into the field of dynamical meteorology and discussed the equilibrium condition of two air-mass rings in juxtaposition. The author intends to develop this theory and to investigate the stability of the atmosphere in a rather generalized form. The equation of pressure adopted by Helmholtz is as follows: where θ is potential temperature, ω absolute angular velocity of the air, ω0 angular velocity of the earth's rotation, ρ distance from the polar axis, r distance from the earth's center, G acceleration of gravity, a radius of the earth, and q, π are certain functions of pressure alone. C is an integrating constant and may be discarded in this problem. Considering two points (r, ρ) and (r+Δr, ρ+Δρ) respectively, as in Fig. 1, the condition of stability is given schematically as follows. If the pressure (in Helmholtz's sense) at (r, ρ) is larger than that at (r+Δr, ρ+Δρ), the atmosphere is unstable for the displacement from the former point to the latter, and stable for the reverse displacement. If the magnitude of pressure is reverse, the above condition of stability becomes also reverse. Thus, the following relation may be adopted as the critical condition of stability: pressure at (r, ρ)=pressure at (r+Δr, ρ+Δρ). (2) Denoting the quantities at (r+Δr, ρ+Δρ) by θ+Δθ, ω+Δω and regarding Δ as very small, the following equation is obtained: Here φ is latitude and Δr is replaced by Δz. Adopting the approximation that ω_??_ω0, ρ_??_a cosφ, ρΔω=Δr, and taking the limit as Δ→0, the final result is as follows: where tan α=dz/adφ. Eq. (4a) is an alternative form of Eq. (4b), and the both are essentially the same. In case of α=90°, Eq. (4a) is reduced to the from: which is the equation of the vertical stability of the atmosphere, while in case of α=0°, Eq. (4b) becomes: which is the equation of the horizontal stability. In case of G=dθ/dz=dθ/dφ=0, the above equations become: respectively, and they coincide with those derived from the circulation theorem of a homogeneous atmosphere (Astrophys. Norveg. 1, No.6, p. 218, 1936).
The coefficients of correlation between the yield of wheat and the weather factors (monthly mean temperature, monthly amount of rainfall and monthly total hours of sunshine) have been calculated by the method previously reported in this journal, for each prefecture in Japan and each month during the cultivating period. The correlation coefficients calculated are shown in tables 1, 2 and 3. 1. The correlation between the yield of wheat and the temperature is positive in the northern district and negative in the southern district. 2. The coefficients of correlations of the yield with rainfall and with sunshine indicate obviously that the rainless, sunny weather throughout the cultivating period is favourable for wheat culture. 3. The correlation of the yield with rainfall is closer than that with any of other weather factors.
Assuming that an upper air current obeys the law of gradient wind and the horizontal temperature gradient of each layer is uniform, the hodograph formed by the upper wind vectors must be nearly a straight line, because the lenght of the hodograph mainly relates to the temperature and the values of the horizontal temperature gradients, and closely to the acceleration of vertical circulation in the baroclinic field. The area enclosed by the wind vectors and the hodograph relates also closely to the movement of the energy and acceleration of horizontal circulations of the air. Under the idea above mentioned we investigated the hodograph of the upper air current and explatined its application.
In this paper it is reported that in winter the normal amount of cloud is large in the region where the value of_??_h⋅∇hT, _??_h and ∇hT being the horizontal component of wind and the air temperature gradient respectively, is negative, and vice versa. Some exceptions, however, may be seen over the sea.