he normal heat sources and sinks in the lower troposphere over the northern hemisphere for January and July are estimated by two independent methods. One is the dynamical method based on the thermodynamic equation and the other is the physical method or the heat-balance method. As for the dynamical method, two layer model under the quasigeostrophic assumption is used in this paper and the results for January, April, July and October are presented and discussed. The results obtained by the two methods show a general agreement qualitatively in the features of large-scale pattern. However, some important discrepancies are found from the more detailed comparison. For example, the heating field obtained by the dynamical method has a more close correspondence with the upper flow pattern than with the surface pressure pattern, while the heating field by the physical method fairly corresponds well with the surface pressure pattern. These discrepancies are thought to be caused by neglect of eddy thermal advection and an incomplete treatment in calculating the vertical velocity in our simplified dynamical method. Throughout the discussion, a more appropriate procedure to estimate the atmospheric heat sources and sinks are suggested.
he behavior of cumulus convection in a prevailing wind with vertical shear is studied by integrating a set of dynamic equations numerically. The motion is considered under the solenoidal condition in a vertical two dimensional plane. Aside from the eddy exchange, the pseudo-adiabatic process is assumed in which the motion is moist adiabatic in saturated ascending air and dry adiabatic in the remaining air. The comparison between both cases, with and without vertical shear, is made concerning the time dependent evolution of convections and their energy conversion. In a prevailing wind field with vertical shear, the axial symmetry of the convection is destroyed and the axis of the convection cell tilts downwind with height. This results in the interaction between the convective motion and the prevailing wind which transforms the kinetic energy of the convection into that of the prevailing wind. Therefore, vertical wind shear tends to suppress the development of the convection in the vertical plane parallel to the wind.Moreover, the discrepancy which develops between the central axes of updraft and the warm regions of the convection decreases the conversion of potential to kinetic energyone which contributes to the development of the convection.
he problem of development of the relatively small scale cyclone (whose characteristic horizontal scale has the order of magnitude of hundred kilometers) is investigated from the standpoint of the effect of latent heat released by condensation through the process of convective action. The appearance of region of hyperbolicity in the so-called ω-equation in balance system or predominancy of very small waves in the solution of primitive equations of motion is avoided by treating the contribution of non-adiabatic heating as a force from outside for ω-equation as proposed by Ooyama (1963). The growth rate of disturbance is obtained analytically in the case of linear problem and also by means of numerical method as a non-linear problem. Comparisons between the growth rates in both cases and discussions on the results are given. Both results indicate that the most favorable wave lengths for development are found in several hundred kilometers. The problem of supply of water vapor from outside is studied, although the dissipation at ground is not taken into account. Suggestion to the control of development of low is proposed and examined in connection with the supply of water vapor.
Blowing dust (Fuhjin) and to a lesser degree dust devils occur with a fairly high degree of regularity each year in the Kanto Plains of Japan during late winter and early spring. The occurrence of blowing dust is in general a post cold front problem, during periods of little or no precipitation.
In order to clarify theoretically the accuracy of method for posing a computational boundary condition at an outflow point in numerical time integration of advective equation by means of the centered finite difference scheme in space, we use the analytical method adopted by Matsuno (1964) who computed and examined the amplitude of reflective computational mode occurred at the boundary to satisfiy the artificial condition by the physical progressive wave. The result shows that the amplitudes of reflective waves in preferred methods which are tested numerically and proposed by the author in the previous paper (1962) are one order of magnitude or more less than those in other methods.