In the early summer or “Baiu” season of 1954, Japan was dominated by abnormal coolness and persistent rain for nearly two months. In the present study, this abnormal weather condition is investigated based primarily on the 5-day mean and 30-day mean 500mb charts with a view to explain it in relation to the hemispherical pressure distribution. As a result, a world-wide stagnation of pressure pattern with a ridge over the Sea of Okhotsk is found to be responsible to the abnormality in the Far Eastern weather. Furthermore, it is shown that the “North High” situation which characterizes the weather in the Baiu season is closely related to the anticyclogenesis over certain climatologically defined localities and also to the position of the jet stream relative to the Himalayas. The findings for 1954 are then compared with the normal climatological statistics and their applicability to the Baiu season in general is proved. Finally, a hypothesis on the mechanism of the Baiu is proposed.
Solving barotropic vorticity equation, the motion of a disturbance of typhoon-type is treated. First, solving barotropic vorticity equation, the deformation of an initially circular disturbance in a changing basic flow with constant shear is treated. Second, the velocity components are given by U+εy0+β/C, V, where U and V are uniform basic flow, ε is constant shear of the basic field, y0 is the northward component of the coordinates of the centre, β is the latitudinal variation of Coriolis factor, C is a negative constant concerned with the scale of the disturbance. Third, equations of motion of the disturbance are obtained. Fifth, the calculated periods and amplitudes of meandering motion are compared with those of actual typhoons.
The system of hydrodynamic equations on the rotating earth, which are the equations of motion, the continuity equation of mass and the thermo-dynamical equation, is derived from the variational principle for the field of the meteorological motion. Another conservative quantities of the absolute vorticity are discussed as a whole on the foundation of variational principle which shall become to be available for the numerical prediction. The merit of the numerical prediction based on Hamilton's canonical equations of the “meteorological field” may be exceedingly remarkable in the long range forecasting. There are some technical “uncertainty” in the long range forecasting. Then, it is necessary to eliminate the small scale disturbances which cause the technical “uncertainty property”. We show the graphical method of numerical prediction based on the Hamilton's canonical equations which take initially space average of the vorticities around the each vortex centre to eliminate the small scale disturbances, as the fundamental study for the extended and long range forecasting.
The inactivation of ultraviolet ray on silver iodide as a sublimation nuclei was examined experimentally, using natural (solar) and artificial (mercury arc) light sources. The silver iodide particles produced at the temperature of 600-700°C were introduced into the diffusing boxes which were equipped by three different kinds of filter, i.e. cutting off the light of wave-length shorter than about λ-240mμ, λ-345mμ and λ-415mμ respectively. Then they were irradiated by ultraviolet ray of natural or artificial source. In order to examine the nucleating properties of silver iodide particles, the small part of them were sampled by a syringe at proper time intervals and then injected into the cold box at the temperature of -14_??_-16°C. Then the number of ice crystals formed in the cold box was counted by visual observation. The logarithm of counted number was plotted against time (minutes) and the decay constant was determined graphically from the slope. On the other hand, the effective energy distribution of ultraviolet radiation which actually exerted on the silver iodide particles in each diffusing boxes was computed, using the properties of filter transmissions and the light source. Thus the decay constant for the light of unit energy in different ranges of wave-length was finally determined. According to these results, the efficiency of inactivation became better, as the wave-length of ultraviolet ray irradiated became shorter. But in the case of solar radiation the intensity of radiation shorter than λ-350mμ was so weak that the actual effect was almost due to the longer side of the radiations. The rate of decay was about 1/500per hour when irradiated through the cellophane-filter by natural light on a clear day.
The Fjørtoft's graphical method of integrating the barotropic vorticity equation is developed under some approximate assumptions. By this method, the relaxation procedure or the Fjørtoft's approximate integration formulae for solving the Poisson type equation are not necessary. And farther, as the changes in Fjørtoft's “quasi-permanent velocity field” are considered by this method, the results of prediction may be improved and time intervals of prediction may be prolonged than the Fjørtoft's method. A graphical procedure for the numerical weather forecast is derived and the results of its application for 12hrs, 24hrs and 48hrs forecast are also shown.
During the period from february 17 to April 10 in 1955 the observations of large haze particles were made at several stations in Asahigawa. The results of observations are as followe: (1) The size distribution of particles in the air is expressed by the formulae dN/dr=const. r-3.6 for 0.5<r<10μ, dN/dr=const. r-4.7 for 10<r40μ and dN/dr=const. r-7.5 for r>40μ, where r is the radii of the particles. (2) The mean density of non-hygroscopic particles is about 0.15. (3) Most of the particles are non-hygroscopic and the ratio of the concentration of non-hygroscopic particles to the of hygroscopic particles increases with particle size.