Observations of the growth and the vertical distribution of natural snow crystals were made in the Mt. Teine region, Hokkaido, in the winter of 1963. Simultaneous radiosonde observations were carried out on the windward side and on the leeward side of the snow crystal observation point. By comparing the condition expected from the type of snow crystals observed with that obtained by radiosonde, some discrepancies were found between them not only in humidity but also in temperature, especially when spatial dendritic snow crystals were observed. The discrepancies may be explained by the difference in meteorological conditions between the falling path of snow crystals sampled and the ascending path of the radiosondes released.
To clasify a seasonal decay of the Ogasawara anticyclone, or the Western Pacific anticyclone, from summer to autumn in the troposphere, the variation of certain isothickness lines, 5, 700 and 5, 800gpm lines, on the 5-day mean thickness chart (1, 000-500mb), was used. It was found that the line of 5, 700gpm is located in the northern part from Japan, and the area surrounded by a certain line of 5, 800gpm covers widely in summer over the Western Pacific on which the Ogasawara anticyclone develops, but in autumn, the line of 5, 700gpm moves toward the south, and reaches the Japan Islands, and then 5, 800gpm line retrogresses to the China Continent, and doesn't come over the Western Pacific again. To study the situation in the stratosphere corresponding to such a tropospheric seasonal transition, the phenomenon of the disappearance of a polar anticyclone surrounded by a certain contour, 31, 760gpm, on the 10mb level, was considered. It was found that the disappearance occurs approximately 25 days prior to the decay of the Ogasawara anticyclone in the troposphere. It was found, moreover that the first day of the disappearance or weakening of a polar anticyclone on the 10mb level corresponds to the date on which the closed high surrounded by a certain contour on the 100mb level located in the eastern part of the anticyclone over Southern Asia begins to stagnate over near Japan, and the Ogasawara anticyclone suddenly decays when the closed high cell starts to move eastward.
In the winters of 1960 and 1961 respectively, two kinds of simultaneous observations andmeasurements were carried out in order to get some data as to the main factors such as the surface electric potential gradient, the charge on snow particles, the falling rate of snow and the forms of snow particles. First, these four factors were measured at two stations installed about 1.2km separated each other along a line on which a shower-cloud often passes. Enough satisfactory data, however, could not be obtained at these two stations, so the surface electric potential gradient and the charge on snow particles were simultaneously measured at another two stations at different altitude, that is, at the Cloud Physics Observatory on the top of Mt. Teine (1023.7 m M.S.L.) and the Paradise Hut about 500m lower than the top. Through these observations, the following points were noted : (1) the origin of the inverse relation between the sign of the surface electric potential gradient and that of the charge on precipitations (2) the space charge effect of the charge on precipitations on the surface electric potential gradient (3) the difference of electrification of shower- and thunderclouds (4) the existence of the difference between the conclusions obtained at the lower and the higher part of the mountain From these observations some interesting results were obtained.
Numerical calculation was carried out to pursue loci of ten circles that had momentum after placed in the closed space. The velocity distribution of them approached to the Maxwellian distribution curve. The distribution of free paths also agreed with the theoretical curve derived from the kinetic theory of gases. Then the “phases” of circles, namely the gaseous phase and the solid phase were defined and transition rules between the two phases were assumed. The growth of a solid cluster could be simulated with statistically reproducible properties that were independent of trials in statistically same conditions. But it was impossible to simulate temperature-dependent properties of nucleation process because of the simplicity of the authors' model.
Westward-moving wave disturbances in the westerlies of the equatorial lower stratosphere recently found by Yanai and Maruyama (1966) are studied in detail by using the data of the special observations over the Marshall Islands area during spring and summer in 1958. Vertical time-sections of upper winds show that the wind direction at about 18 to 24 km height oscillates between southwest and northwest with a period of four to five days. Synoptic analysis shows the existence of the large-scale wave disturbances moving westward against the westerly flow at a speed of about 2,000 km/day. The wave-length may be as long as 10,000 km. The phase lines tilt westward with increasing height. Power spectral analysis of meridional wind component indicates that the oscillation is prevailing in the lower stratosphere confined close to the equator. By removing the basic flow through a simple procedure, the disturbances are found to take the form of eddies centered on the equator. Pronounced eddies observed in April 1958 are investigated in particular to determine threedimensional structure of the disturbances. The west ward propagation of the disturbances is apparently owing to the 13-effect. The phase velocity and the flow-height pattern of the disturbances are compared with those of the theoretical barotropic-divergent equatorial waves discussed by Rosenthal (1965) and Matsuno (1966).
Stability properties of the stratospheric polar vortex deformed under the influence of external forces are examined by use of the barotropic vorticity equation and energy equation. Time integration of perturbation equation as an initial value problem shows that a barotropic instability corresponding to deformed vortex exists and this instability increases when the vortex is more deformed. Comparison of stability properties between the northern and southern hemispheric polar vortex is shown by numerical model, and the results of computations show that the northern hemispheric type polar vortex with wave number 2 is more unstable than the southern hemispheric type vortex with wave number 1, and the breakdown is shown for the former case. Some theoretical considerations are also given concerning the kinetic energy equations for our model. It is found that total kinetic energy much increases when the phase of perturbations is L/4 (L: wave length) different from that of the basic flow.
The vertical structure of the stratospheric temperature field and its time variations were analyzed throughout the period of the sudden warming phenomenon by use of the daily synoptic weather maps published by Free University of Berlin. The sudden warming in January 1963, which was observed over southeastern Canada, was the chief study with further analyses of the sudden warmings of January 1958 and March 1965. The vertical cross sections of temperature and its time variations were shown along the western semi-circle at 50°N in the five levels from 300mb up to 10mb. It is found from these analyses that the vertical trough line is strongly tilted westward above the 50mb level with increasing height, where isotherms are nearly parallel to the tilted trough line, and this disturbance, as a whole, moves westward (or northwestward) when the warming reaches its maximum. As the result of the westward movement of the tilted axis, the vertical time-section at one station shows that the warming first occurred in the upper level and moved downward. On the contrary, vertical cross sections of the time change of temperature show that the warming appears first at the 100mb or 50mb level and then it propagates upward with a phase speed of about 10mb/day. The upward propagation of the warming is also verified by the vertical cross sections along longitude 50°W from the North pole to 20°N. Thus the sudden warming phenomenon is considered to consist of two stages, i, e., the intensification stage in which the disturbance propagates upward from lower to the upper stratosphere, and the migratory stage in which it moves westward in connection with the breakdown of the polar vortex. These features of the warming phenomenon are common at least to these three cases.