Abstract
It is well known that a polar continental airmass becomes unstable when it travels over warm sea. The cloudy weather of Formosa and the snowfall on the coast of Japan Sea in winter are explained by such transformation of the air-mass which is brought by the monsoon from the Asiatic continent. In this paper, such transformation of the cold and dry air-mass by traveling over warm sea is numerically calculated by the help of adiabatic charts under the following assumptions.
1) The temperature of sea water is constant.
2) The process in the atmosphere is adiabatic.
3) The air-mass has no vapour when it starts from the continent.
4) The lower layer of the atmosphere becomes unstable up to some height by the heating from the sea, so that astrong convection is expected, and hence mixing ratio and equivalent potential temperature become constant in that layer.
5) The amount of evaporation per unit time per unit area from the sea is given by dm/dt=A(E-e), where A is a constant, E maximum vapour tension at the temperature of the sea water, e vapour tension in the air.
6) the amount of heat supply per unit time per unit area from the sea is given by dQ/dt=B(Ts-Ta).
The results obtained are as follows.
1) Clouds begin to form in the air-mass at a certain distance from the continent and the cloud height becomes lower and its thickness becomes larger as the air-mass travels over the sea.
2) When the temperature difference between the air-mass and the sea water is large, clouds are easily formed and their thickness is large.
3) The temperature of the air riese with the traveling, by the heating from the sea. However, the temperature difference between air and sea is comparatively large, say 6°C, even after a pretty long journey over the sea.
