Inhabitants in Japan suffer f rom strong winds and heavy rainfalls in the typhoon almost every year. Investigations on typhoons and depressions have been sedulously made by the investigators in the Central Meteorological Observatory and in the geophysical institutes of universities. In recent years, the development in the observational techniques with Radiosonde and Rawin has made it possible to obtain reliable observational materials in an area of typhoon and even close to or even in the eye of a typhoon. In the typhoon season of 1951, the Central Meteorological Observatory of Japan started the Typhoon Research Project which included the aerological and extraordinary surface observations. In this synthetic paper the author intends to report on the recent researches on typhoons in Japan.
Pyramidal waves in the “ eye ” of typhoons are described in many meteorological texts. Numerous exmples are given indicating that the most dangerous, pyramidal, mountainous and confused seas are those found in the right or dangerous semi-circle of typhoons and not those found in the calm center.
The following stability criterion of a motion of a circular vortex embedded in a geostrophic general current is evaluated by means of the parcel method, i. e.: where RN is the Richardson Number, λ the Coriolis parameter and υθg, the tangential component of a geostrophic general current. This stability criterion is evaluated for the case that the cyclonic circulation of circular vortex develops. This shows that the conditions for the formation of tropical cyclones can be described as the combined effect of the vertical shear and the static and dynamic stability. It is emphasized that the barotropic state of the upper atmosphere is very favorable for the formation of tropical cyclones in the atmosphere of static instability. An example on August 1950 is also discussed.
The geostrophic angular momentum transfer vector on the 500 mb level is calculated over the Far East. The angular momentum convergence in a sector of 10 degrees in latitude and 30 degrees in longitude is compared with the local zonal-index tendency in the same area. Good relation is found between them on the variation with a period of several days, but only 30% of the horizontal convergence of angular momentum appears in the local change. Also,45-day mean angular momentum transfer vector is calculated. Its horizontal convergence shows a remarkable locality having such a value as suffices to cause the zonal velocity change 6 m⋅sec-1 in a day. The eddy transfer has northward component almost everywhere in our region, but is smaller than the transfer due to mean wind.
The purpose of the present paper is to examine the possibility of numerical prediction by Fourier Series and to analyse the atmospheric structure. Let us multiply the vorticity equation by a periodic function and integrate it from 0 to 2π (along a latitude circle), and we can obtain certain equations. Namely, the following results could be derived from numerical calculation on the barotropic model, i. e. 1) Numerical prediction is possible by the Fourier Series with the harmonics from n=1 to n=9. 2) Correlation between the zonal flow of component-wave vorticitv by the mean flow and the meridional flow of absolute mean flow vorticity by that component wave is negative at middle latitudes from 55°N to 40°N, and positive at 60°N. 3) The same relation as in 2) can be found in the interaction between the component waves. 4) The non-linear effect at lower latitudes than 55°N is reverse to that at 60°N, which, coupled with that shown in 2) and 3), tells us that 55°N latitude circle, roughly speaking, forms a kind of nodal line. 5) Magnitude of time change of amplitudes of long waves can not be explained by the barotropic and non-divergent model, perhaps due to the upward motion and horizontal stability changes caused by the topography.
In our previous reports, stochastical studies were tried for the fluctuations of monthly mean temperature and pressure for August at the various stations in the neighbourhood of Japan. Significant periodic fluctuations of about 7-years were detected then. Such periodicity was distinct in the middle latitudes and was presented in the zonal oscillation of North Pacific High. In this paper, we have tried the statistical investigation for the periodicity in monthly mean situation in the Northern Hemisphere. The results obtained are as follows. 1) The periodicity of about 7-years for the monthly mean pressure and temperature for August are stochastically significant in Central and Southern Europe, and for August mean pressure in Southern India, Java and Sumatra.2) The periodic fluctuations of 7-years for August mean pressure in Europe are everywhere in phase, but for the temperature, they are inverse between Greenwich and Alexandria.3) The periodic fluctuations of 7-years for August mean pressure in Europe and India are also in phase.4) The periodic fluctuations of 7-years for August. mean pressure in Europe are ahead of Japan for several years.
Two large scale experiments on cloud seeding were made in the summer of 1952 along the present author's suggestion that silver iodide smoke should be released in less turbulent wind at a high level by the seeding operation on the top of a high mountain. In the experiment of Tokyo Electric Power Company the charcoal burners of silver iodide were employed, and in the experiment of Chubu Electric Power Company the improved light oil furnace type smoke generators after the present author's design were employed. The seedings were more or less effectual in many cases. Two excellent results are illustrated. The lateral and vertical spreadings of silver iodide smoke by turbulent diffusion in the air were known to some extent from the results of the experiments.
The amount of atmospheric ozone was measured at Tokyo during the period from January 1951 to September 1952, using a chromium phototube and glass filters. The ozone amount showed a marked seasonal variation having the maximum value in late spring (about 0.28 cm) and the minimum in autumn (about 0.22 cm). Relations between the deviation from the mean annual variation of the ozone amount and surface high or low pressure were studied. Positive deviations were found near and in front of travelling anticyclonic centers, while negative ones were generally found near the centers of surface low. It seems that a close correlation exists between the ozone amount deviation and wind direction or air temperature in the lower stratosphere. Downward motion of the air in the lower stratosphere, which is supposed to occur above the front side of a trough at 500 mb level, will result in positive deviation, and upward Motion above the rear side of a trough cause negative deviation.
According to test resultso btained in March 1953, an actual Speedovane is equipped with electric heaters of total capacity of ca.700 watts and tested for nine days in April 1954 on the summit of Mt. Fuji (station height,3,773 rn above sea level). The heater capacity is confirmed sufficient for the anti-freezing purpose in ordinary icing conditions to be encountered at weather stations in Japan.