In section 2, the physical significance of the time-averaged equations of motion is discussed. In the time averaged vorticity equation, the terms expressing the vertical transport of vorticity, the dissipation of vorticity due to friction, and so on, become important in their magnitude. As for the time-averaged thermodynamic equation, the magnitude of the term expressing the heat transfer due to horizontal disturbances is about the same order as that due to mean horizontal velocity. On the contrary, the heat transfer due to vertical disturbances is extremely small as compared with that due to mean vertical velocity. In section 3, we compute the mean vertical velocity and the mean supply of heat during the rainy season. An interesting feature in the patterns is the existence of a marked zone of cooling and of a pronounced downward motion near the so-called Okhotsk high. In section 4, the mean stream function and the mean velocity potential are obtained. Utilizing the mean velocity potential, the vertical distributions of divergence at the southwestern part of the Okhotsk high are analyzed.
The behaviour of the truncation errors in the numerical prediction using grid points, is discussed taking into account the scale of the perturbations. When we forecast by the ordinary numerical prediction method the path of the relatively small cyclone such as the typhoon, the velocity of the center is known to become smaller than the observed value. We conclude that this fact can be explained by the behaviour of the truncation errors.
Records of daily total of solar radiation measured on a horizontal surface for consecutive three to seven years are available for about forty stations in Japan. Using these data, yearly and seasonal mean isopleths of solar radiation are drawn. In the results the following features are to be pointed out: 1) The distributions are affected by the meteorological fa c tors rather than by latitude.2) The amount of solar radiation is larger in the inland district than near the sea.3) The minima of solar radiation in the Tokyo and Osaka districts are remarkable.4) The seasonal variation of the amount of solar radiation is largest in summer and then in spring, autumn and winter in the order of magnitude.5) The annual variations of solar radiation are mainly brought about by the conditions in summer.
Showa-Shinzan, one of th e Belonite-Volcanoes, born (1943-1945)in the eastern part of the Volcano Usu (in the South-western part of Hokkaido, Japan) is famous in the history of volcanoes in the world. This volcano erupted in a farm-land and further developed a lava dome (Spine) in the central part. It is a Pelée-type one, and its developing process was clearly observed for the whole period. Some remarkable earthquake swarms occurred during the volcanic activity, and the major ones among them were recorded by seismographs even at a station about 800 km apart from the volcano. The author investigated the relations betwee n the occurrence of earthquakes and the formation of Showa-Shinzan and tried to find some clues to the volcanic mechanism. In this first paper, after an investigation of the characteristics of earthquake swarms recorded on the seismographs in Muroran, Mori and Sapporo (epicentral distance: 25-69 km) and the relation of the volcanic activity therewith, some interesting results were obtained: 1) Daily earthquake frequency diagram for the whole period of twenty three months were prepared for the first time. 2) These earthquakes were clearly divided into the following three stages: ( i ) Pre-volcanic stage: In this stage there was no eruption, and remarkable earthquakes occurred around Volcano Usu frequently. The relation between the maximum amplitude (A) in these earthquake swarms and their frequency (N) was expressed by NAm = const. where m is about 1.8, similar to that of the tectonic earthquake. Moreover, the migration of the hypocentres of these earthquakes showed an intimate connection with the course of the magma intrusion. (ii) Stage of eruptive activity: A violent eruption occurred in the central part of the rising area. The extremely shallow earthquakes during the period of six months including just before and through the eruptive activity were proved to have been originated at the area adjacent to the newly formed crater. (iii) Birth and developmen t of lava dome (spine): The lava dome grew and developed without eruption, accompanied with numerous earthquakes. The earthquakes, which differed greatly from those at the former two stages, began to occur almost simultaneously with the end of the eruption and the frequencies of the earthquakes during the following twelve months corresponded closely to the speed of the development of the lava dome. The value of m in this case was 3.5. 3) Process of magma intrusion, increase of magma viscosity a n d their relationship with the feature change of earthquake swarms were investigated. The possibility of predicting volcanic activity Volcano Usu by seismograph at stations up to approximately sixty or seventy kilometers from the volcano is suggested.