Characteristic features of mountain and valley winds are investigated by two-dimensional numerical model. It is found that the mountain and valley winds on the series of plain, slope and plateau with scale of 50-100km consist of two systems. One is a circulation caused by differential heating between the air above the plain and that on the plateau, and the other is a slope wind.
In the daytime, the dominant flow is a plain-to-plateau flow. Its front penetrates about 100km into the plateau. The intensity of the flow is well correlated to the temperature difference between the air above the plain and that on the plateau. If the horizontal scale of a slope is smaller than, or equal to that of the plain and of the plateau, the up-slope wind modifies the plain-to-plateau flow in two ways: A slight increase of the maximum wind velocity in the case of high plateau, and a slower penetration of the flow onto the plateau in the case of low plateau.
In the night time, the down-slope wind is strong and confined to the thin layer on the slope. The cooling over the plateau results in a weaker plateau-to-plain flow. The intensity of this flow is also related to the temperature difference between the air above they plain and that on the plateau. The intensity of the down-slope wind is well explained by the linear theory by Prandtl (1942) (see Sutton (1953)).