A three-dimensional numerical model of the land and sea breezes allowing mountain effect was developed. The system of governing equations is so-callde Boussinesq hydrostatic one, using z*-coordinate system as a vertical coordinate which refers the lower and upper boundaries to the ground surface and the upper surface of the model, respectively.The model atmosphere with a vertical scale of 2800 m and a horizontal scale of 217.5 km is divided vertically into 12 layers and horizontally into 30*30 grids with 7.5 km mesh.It is assumed that the surface temperature on sea is constant but that on land changes sinusoidally with a constant diurnal range around the mean temperature at each level. Temperature contrast induced by the above mechanism causes the land and sea breezes and the mountain and valley winds. By using this model, some experiments were carried out for studying the influence of mountains on the land and sea breezes in the case of the Kanto district.In mountain-free model, the most prominent sea breeze circulation was restricted within about 40 km from sea shore. The local circulations simulated by the model including mountain effects are in good agreement with observation in the Kanto district. The experimental results show that the mountain and valley winds appear earlier than the appearance of the land and sea breeze circulation.But this phenomenon is not yet confirmed by observation.

The nocturnal low level jet, which appears over the southeastern part of the Kanto Plain, is simulated using a three-dimensional numerical model of the local winds. The results agree well with observations of the horizontal and vertical distribuitons of the jet. The diurnal variation of the jet generally agrees with the observation.However, the amplitude of the diurnal variation is a little smaller and the maximum wind velocity appears a few hours earlier than the observation.From some additional numerical experiments, e.g., without the thermal effect of the ground, it is found that the primary factor of the low level jet formation is the mechanical effect of the mountains in central Japan upon the large scale wind. The thermal effect of the mountains enhances the low level jet and produces a diurnal variation. The turbulent stress is also important to the diurnal variation of the jet, but the inertia oscillation, which is generated by the large scale wind and the diurnal variation of the stress, is unlikely to be a primary factor of the jet formation.

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Using observed results, the some characters of the fall winds and the Dashikaze (i.e. winds that blow out of the narrow valley) are described, and the existence of an inversion layer above is emphasized.On the basis of these facts an averaged system of equations of air flow under the inversion is derived and then the natures of steady flow in the channel with variable width and height of the bottom are studied.As a result the flows over the mountain and through the narrow valley are found to be affected in the same way, and if the difference in the inversion height exists between windward and lee of these obstacles, then the violent wind may arise in the lee side (or exit part) . It is shown that the above theoretical results agree qualitatively very well with some observed

The system of partial differential equations which shows the one-dimensional unsteady airflow over the mountains under the inversion layer is hyperbolic type, and has two families of characteristic lines. Using this nature, the system of basic equations is integrated numerically along each characteristic line. The following three initial conditions are given : (1) subcritical flow for all intervals, (2) subcritical flow for all intervals, but critical flow at the mountain crest, and (3) supercritical flow for all intervals.In all cases the bight of the inversion increases on the windward side and decreases on lee side. And a jump arises on the lee side after some time-steps.The higher the initial speed, the farther downward the jump appears, which suggests the possibility of a fall wind. That the swell is higher with increasing initial speed explains the abnormal pressure difference between the windward and the lee side. In order to determine the position of the lee side jump, a method for extending the characteristic lines through the jump region is devised and described. Some characteristics of propagation of the jump or drop whose shape is unchanged are discussed analytically.These analytical results can explain the propagation of the disturbances observed in numerical solutions.