The conception of the artificial control of retrogressive ultra-long waves, as shown by Wiin-Nielsen, is applied to the entire heights of the atmosphere, and then the essential condition to control the retrogression is obtained. The condition is that the variation of the isobaric height must vanish at the top of the atmosphere, if the static stability is proportional to p-2. Using this upper boundary assumption, the simplest 3-level model is constructed and is compared with Wiin-Nielsen's model. These are similar in the result, but some ambiguities of the so-called μ term are excluded in our model. Lastly the physical meanings of the upper boundary assumption are considered. As the result, it is inferred that such a condition exists in the stratosphere.
The downdraft in Convective shower-cloud is simulated by numerical integration of hydrodynamic and thermodynamic equations, the fall of raindrops being included. The behaviors of downdraft in two cases are computed : in the first case, atmosphere is initially at rest and in the second case, horizontal air-flow with vertical shear initially exists. The results of computation show that though upcurrents follow the preceding downdraft in both cases without and with wind shear, the upcurrent in the latter case differs from that in the former case in the following respects. In the case without wind shear, the upcurrents of weaker intensity take place in both sides of the cloud only as compensating current and gravitational oscillation. In the case with wind shear, stronger upcurrent is formed in front of the cloud. This upcurrent is forced by stronger convergence due to both diverging current originated from the downdraft and the larger horizontal momentum which the downdraft transports from upper. It is concluded from computations that vertical wind shear organizes the release of instability energy in convective system, though the conversion rate of potential energy into kinetic one in the whole region is less than that in the case without wind shear.
In this paper are presented the results of detailed analyses of remarkable pre-frontal precipitation zones* during a winter season. The analyses are then compared to prefrontal squall-line situations. Then the general aspects of pre-frontal precipitation zones are described in some detail. It is concluded that in the United States to the east of Rocky Mountains, formation of an extensive precipitation zone in a warm sector of a cyclone is a typical phenomenon. It is shown that formations of such extensive pre-frontal precipitation zones are related to regular synoptic scale disturbances aloft rather than a local mechanism which exists only very near to the ground. Roles of static stability are examined and found to be not so important for formations of such organized precipitation systems. It is also pointed out that interaction between the cold frontal surface and the precipitation system may be no more than a secondary importance.
The electric charge on falling snow crystals was measured in the process of their melting. The results of measurements showed that the snow crystals obtained positive charge of an order of 10-4 esu on the average and the majority of snow crystals changed their sign of charge from negative to positive. It was observed that numerous air bubbles were produced in melting snow crystals with a subsequent erruption from their melting surface. It was also confirmed that the more complex the crystal shape, the more positive charge the crystal acquired in the melting state. From the results of the measurement, it was suggested that snow crystals obtained positive charge in the course of melting when air bubbles errupted from the melting snow crystals, carrying off negative charge.
From the experimental and observational results to date (Magono and Kikuchi, 1963, 1965), it has been known that snow crystals and ice specimens acquire some positive charge during their melting process. As it is thought that air bubbles which contained in snow crystals and ice specimens have some role to the mechanism of charge generation in their melting process, especially in this paper, the relationship between air bubble concentration in ice specimen and positive charge generation in the specimen during the process was confirmed experimentally. As a result, it was found that the positive charge acquired in the melting process was approximately proportional to the air bubble concentration contained in the ice specimen, and it was noted that the charge depended not only on the total volume of air bubbles in the specimen but also on the size of each bubble. In this experiment, the diameters which contribute to the mechanism of this charge generation ranged from several μ to 150μ with the mean volume diameter of 52μ. And big air bubbles which the equivalent volume diameter is larger than 1 mm did not contribute to the mechanism. Accordingly, it was noted that a great number of small air bubbles are important in the charge generation in the melting process.
Following the previous papers (Magono and Kikuchi, 1963, 1965; Kikuchi, 1965), studies on positive electrification associated with the melting of the ice specimen were carried out by experimental method. During the experiment, it was observed that a number of droplets burst from the melting surface of ice specimen. And it was observed that these droplets carried negative charge, and the magnitude of the negative charge was in the order of 10-7 to 10-5 esu. On the basis of this result, the relationship between air bubble concentration and positive charge in melting ice (Kikuchi, 1965) was clarified.
Ice crystal growth from vapour was studied using a small, diffusion cold-box composed of thermoelectric cooling panels. Within a range of -40 to -90°C, the crystals have a prismatic habit of growth, either in solid prisms or in hollow sheaths, depending upon the saturation ratio of the vapour. Long prisms and whiskers are often observed at low supersaturation, between -45 and -50°C. Pyramidal faces appear at the end of prisms between -50 and -90°C. At very high supersaturation, around -90°C, the growth of a peculiar type of dendritic crystals are observed.