A large cloud chamber of about 15 meter high made possible to observe ice crystals grown in free fall. During the experiments carried out by using several seeding methods it was found that the seeding method to use a cold body produced not only usual ice crystals of hexagonal shape but also several kinds of very interesting skeleton ice crystals of non-hexagonal shape. As a cold body a metal rod chilled by liquid nitrogen or by dry ice was used. The temperature range at which those crystals were found were -1.9--11.1°C and <-20°C. These ice crystals are thought started their growth at the special initial conditions of extraordinary high super-saturation. Their growth modes are mainly determined by air temperature as shown by the fact that those grown at high temperature (-1.9--11.1°C) and those grown at low temperature (<-20°C) were very different in appearance. From a crystallographic point of view the formation of these skeleton ice crystals of nonhexagonal shape presents the three important facts as follows. One is that initial condition of ice crystal formation is possible to affect the later growth habit seriously, another is that an ice dendrite growing in the ‹112ι› direction is possible to be understood as a growth along skeleton arm and the other is that the growth of both inside plane and pyramidal plane are possible. (The definitions of skeleton arm and inside plane are presented in section 3)
Examinaticn of basal plane surface areas of sectorlike, stellar and dendritic ice crystals found in natural clouds was made. Empirical relationships describing basal plane surface area and diameter have been developed. The results suggest that the surface area of the basal face for certain crystals is nearly constant, and thus independent of the crystal size.
The observations at the city and the suburbs of Asahikawa disclosed the areal distributions of supercooled dense fog and ice fog. At the central part of the city a supercooled dense fog seemed to be converted to an ice fog by artificial ice nuclei even at -14--17°C, when in the suburbs sometimes stable supercooled fog was observed at -26°C. It was also confirmed that ice crystals near the vapor sources grew sometimes so large that they might be called snow crystals.
Convective patterns of silicone oil in a plane Couette flow were observed for various vertical shears and at various Rayleigh numbers. A circular channel with a rotating upper disk was used to produce a shear flow and convective motions were generated by heating the bottom and cooling the top of the channel. The result indicates that there are three convective regimes: cellular patterns which appear at large Rayleigh numbers and for small vertical shears, longitudinal rolls which appear at small Rayleigh numbers and for large vertical shears and intermediate convective patterns in the domain between the cellular and longitudinal-roll regimes. The critical shear which separates longitudinal rolls from cellular patterns increases with the Rayleigh number. The transverse rolls were not observed in the range of the vertical shear considered here. The phase velocity of the convective cells was found to be about one half of the velocity of the upper disk. The transition of convective patterns was observed using a modified channel which has irregularities at the bottom surface to enhance the occurrence of the transverse rolls. It was found that the critical shear is increased by the presence of the bottom irregularities and that existence of transverse rolls with a large amplitude at the initial state did not change characteristics of the convective regimes.
In order to investigate the response of the Ekman boundary layer of the ocean to fluctuating wind stress, we solved analytically the time dependent equations of motion as an initial value problem by extending the Fredholm's solution. The frequency distribution of the time average value of the surface horizontal velocity is numerically estimated from the analytical solution. The calculated amplitude of response is compared with that due to the steady wind stress. It is shown that in general the responded amplitude of the Ekman boundary layer to the transitory wind stress is smaller than that to the steady wind stress except the case where the frequency of the forcing wind stress ω equals to the inertial frequency ƒ. For ω which is close to, but not exactly equals to zero, one would overestimate the amplitude if one averages it over a shorter time interval than the period of the forcing, 2π/ω. For ω=ƒ, the magnitude of the oscillatory velocity component increases proportionally to the square root of the time elapsed.
During the period of the second Experiment of the Severe Rainstorm Research Project, July 3-July 10, 1969, the “Baiu” front with continual heavy rainfall lay almost steadily over the Japan Islands. The total amount of rainfall over the central and southern Kyushu during this period exceeded 500 mm. Some characteristic features of the "Baiu" front are revealed by analysis of averaged fields of various meteorological elements over the one-week period. Although the Baiu front is formed along the boundary between the monsoon and the continental polar air masses, its structure is characterized not by any remarkable concentration of horizontal temperature gradient but by the existence of supergeostrophic low-level jet stream. The strong southerly flux of water vapor toward the front seems to be deeply related with the convective activity and therefore with the heavy precipitation in the vicinity of the low-level jet stream. It is suggested that downward transfer of horizontal momentum by cumulus convection maintains the low-level jet stream. A mid-tropospheric warm and moist belt, found above the low-level jet, seems to be resulted from the convective vertical transfer of heat and water vapor. Intermediate-scale disturbances developed successively in the northern side of the low-level jet stream, where the cyclonic wind shear is strong and the thermal stratification is nearly neutral. The kinetic energy of intermediate-scale disturbances is concentrated within the lower troposphere with a maximum energy density at about 800 mb just to the north of the low-level jet axis.
Typhoon Cora, 1969, took the extratropical appearance over the Japanese Islands. This aspect is analyzed from the view-point that Cora is the compound system of tropical and extratropical cyclones. The synoptic analyses show that the participant extratropical cyclone pre-existed independently far from Cora and approached Cora to form the compound system with her, and that it usurped Cora at last, resulting in her apparent extratropical transformation. This aspect is different from those, previously investigated as the complex system, in which the participant extratropical cyclone is induced on the pre-existing front which invades into the inner region of typhoon area. The synoptic behavior of participant extratropical cyclone of the compound system is brought into focus to confirm the condition favorable for its deve'opment.
The problem of diffuse reflection and transmission of the solar radiation by the earth's atmosphere is discussed taking into account the effects of polarization and inhomogeneity of the atmosphere. Firstly, we discuss the formulation of basic equations for the reflection and transmission matrices which describe the intensity and state of polarization of the diffusely reflected and transmitted radiation. Some revisions on the equations for a homogneous atmosphere derived by Chandrasekhar and Sekera have been made. The symmetry relationships for the reflection and transmission matrices are also examined and presented in a more general form than that given by Hovenier. We then develop a method for the numerical solution by extending the matrix method proposed by Towmey et al. to include the effects of polarization and inhomogeneity of the atmosphere. After some modifications of the reflection and transmission matrices, algebraic equations satisfied by these modified matrices are derived. These derived equations enable us to compute the properties of thick layers by building them up from thinner sublayers. Discussion is also made on reduction of the solution from that of the problem with underlying surface which reflects the incident radiation to that of the standard problem without reflecting surface.