Abstract
Various natures of summer weather in Far East Asia were investigated for the purpose of short and long range weather forecasting, and the results are summarized as follows.
1) The alternation of weather is slow and the diurnal variation of various meteorological elements is quite distinct. Hence, daily weather is predicted by air-mass analysis of morning observation.
2) One of the most important factor which controles the weather is Ogasawara high. Most depressions in summer, say, typhoon, one of the most distructive storm of the world, travel clockwise around Ogasawara high. If there is no depression about Ogasawara high, tropical maritime air-mass is brought from Ogasawara and usually continues fair weather.
3) On an average, six depressions lie around the Ogasawara high, and 5 days periodicity of pressure is explained by the drift of the depression due to the upper wind.
4) The velocity distribution at the surface in Ogasawara high is given by provided that circular symmetry of Ogasawara high is assumed, where V is velocity, r distance from the center, Vo, ro are constants. Such a distribution agrees with the distribution of pressure as it should be and the descending current in Ogasawara high is estimated to be about 2.5mm/sec.
5) Thermodynamical nature of Ogasawara air-mass is calculated from the condition of the equilibrium of energy transfer of various kinds and the lapse rate of temperature is calculated to be about 0.5°C/100m.
6) When the cold air of high latitude invades in low latitude, say, about N 40°, rainy weather is expected at northern part of the main island of Japan.
7) Water vapor which evaporates from sea in the domain of Ogasawara high can be considered to diffuse in all directions and the coefficient of diffusivity is calculated to be about 3×1009cm2/sec
8) Thunder storms in the season are classified into two kinds; one is the outbreak of instability due to invasion of cold air, the other due to ascending current caused by insulation, and they have different structure. It is shown further that every strong heat thunder storm has warm sector like a polar front depression which is important for the practice of the prediction of heat thunder storm.
