The atmospheric electric conductivity and potential gradient were measured aboard the Icebreaker “Fuji”, an antarctic observation ship, during her test cruise around the Japan Islands in October 1966. The electric conductivity was found to vary with distance from the coastline, reflecting the effect of atmospheric pollution extending from land sources over the ocean by diffusion. Analysis of the data obtained shows that the conductivity was determined almost uniquely as a function of distance from the coastline when the weather was clear.
According to Mullins and Sekerka's perturbation method, shape instability of ice crystals growing in a cold chamber was calculated under more general and more proper conditions for ice crystal growth in a vapor phase. The sublimation coefficient was taken into consideration. Result of the calculation was compared with experimental results on shapes of small ice crystals (the order of the size was tens of microns or less) in air under low pressure, small ice crystals in the atmospheres of hydrogen, carbon dioxide and argon-helium mixture. Shapes of carbon dioxide crystals and ammonia crystals were also compared with the calculation. It has been pointed that difference between shapes of ice crystals grown in various atmospheres is mainly attributable to difference in the diffusion coefficients of water vapor under conditions of small value of the sublimation coefficient, and partly attributable to difference in the thermal conductivities of the gases. Difference between shapes of crystals of ice, carbon dioxide, and ammonia is probably attributable to difference in degree of supersaturation and surface tensions.
A measurement was made on the fall velocity of ice crystals at Asahikawa, Hokkaido, in February 1968. The ice crystals were freely falling and drifting in supercooled fog at temperatures of about -20°C. Prevailing forms of the ice crystals were the minute assemblage of plates, the germ of skeleton form and the irregular germ. The fall velocity was measured by the photographs of their trajectories and by the simultaneous observation of wind speed, and it was found that the ice crystals with a mean size of 103 microns fell, as a whole, with vertical speed of 10.7cm•sec-1. This value was compared with the calculated fall velocities of a sphere and a circular disk of the same diameter as the ice crystals observed.
A stability of axisymmetric flows in the rotating fluid annulus with respect to the wave perturbations is studied by the numerical time integration of linearized hydrodynamic equations. Firstly, two steady axisymmetric flows are established by integrating nonlinear Boussinesq equations. One (Case (C)) is supposed to be located in the upper symmetric regime and the other (Case (B)) in the wave regime. Then, the stability of the two axisymmetric flows with respect to the wave disturbance with an assumed zonal wave number is examined by integrating a system of linearized perturbation equations as an initial value problem. The axisymmetric flow for Case (B) is shown to be unstable with respect to the disturbance with a wave number 8. The developed wave is essentially similar to the classical Eady wave. Near the upper and lower boundaries, the structure of the wave is modified to form the Ekman layer balance. Energetics of the developed wave is also discussed.
The stability of medium scale disturbances is discussed taking into account the latitudinal variation of the perturbations. In connection with this problem, we introduce three parameters, i.e., the Richardson number Ri and the Rossby numbers Rx and Ry in the longitudinal and latitudinal directions respectively. Theoretical consideration shows that according to RiRx2_??_Ry2 (1- Ri) the baroclinic or shearing instability predominates and it is also shown that the growth rate of disturbances in the latter case is larger than that in the former case. Numerical experiments are also performed in two cases where Ri≈2 and Ri≈1/2 in the lower atmosphere. The case where Ri≈1/2 presents the similar situation with the rapid cyclogenesis of medium scale disturbances along the surface front.
An attempt is made to separate large-scale equatorial waves into the ODD-mode and the EVEN-mode waves using time series data of four Pacific stations which are located nearly symmetrically on both sides of the equator. At least eight distinct waves are isolated by the spectrum analysis of symmetric and antisymmetric components of winds with respect to the equator. Most of the ODD-mode waves propagate eastward and exhibit only zonal wind oscillations indicatingthat they are Kelvin waves. There are two ODD-mode waves that may be identified with Rossby waves, because they show westward propagation relative to the air. All the EVEN-mode waves (seemingly the mixed Rossby-gravity waves) including the 4- to 5-day waves found by Yanai and Maruyama (1966) move westward. The vertical amplitude distribution and the vertical phase propagation are examined for each of the isolated waves. All the waves show maximum spectral density at about 12-14 km levels and the inclination of phase lines indicates upward propagation of wave energy above the level of maximum spectral density and downward energy propagation below the level. Some waves have very large inclination of phase lines, i. e., very short vertical wavelengths. The observed horizontal wavelength by use of two pairs of stations is compared with the calculation using the frequency equation of Matsuno (1966) and Lindzen (1967) based on the observed period and vertical wavelength.
We studied the contributions of eddies with various time scale to the covariances of the zonal wind component, temperature and geopotential height with the meridional wind component in the tropical troposphere by the spectral analysis of time series data of Pacific stations for April-July 1962. In the equatorial region disturbances with periods near 4 days play an important role in the covariances. On the other hand, disturbances with period near 6 days and those with periods longer than 10 days mostly contribute to the covariances in sub-tropical latitudes (near 20°N). Average horizontal transports of zonal momentum, sensible heat and potential energy due to transient eddies and partial contributions of disturbances with periods near 4 days to the transports are examined as functions of latitude and altitude. Strong energy fluxes due to disturbances with periods longer than 6 days enter into the tropics from higher latitudes. This results agrees with that obtained theoretically by Mak (1969). Equatorward heat fluxes exist in the lower and the middle troposphere. Large poleward heat fluxes are observed in the upper troposphere. In higher latitudes, contributions of disturbances with periods near 4 days to the horizontal transports are small, but in the equatorial region these become large. A partial estimate of the energy transformation process of eddies contained between the equator and 15°N. Large energy fluxes (pressure work) from higher latitudes converge in the equatorial region. The eddy kinetic energy is transformed to the zonal kinetic energy and the eddy available potential energy is transformed to the zonal potential energy. The convergence of energy flux from higher latitudes is one order of magnitude larger than both energy conversions from eddy to zonal energy and from eddy to zonal available potential energy.
The mean monthly brightness values pertaining to India and neighbourhood (50°E to 100°E and 20°S to 40°N) as available from ESSA III and ESSA V satellite global data for the period February 1967 to January 1968, have been analysed and studied. The zone of maximum brightness, which indicates the region of most intense clouding in the lower latitudes, has been found centred at 7.5°S from February to April, shifted progressively northward reaching 22.5°N during July-August and then retrieved southward. The patterns of brightness distribution considered season-wise have shown remarkable continuity from latitude to latidute. The findings help suggest that the basic flow of the Indian summer monsoon stems from regions south of the equator.