The Air Masses of Japan (Continued)

[摘要] 1) The polar continental air-mass originates in Manchuria and Siberia and comes to the Japan proper as the Northwest Monsoon and further reaches the Philippines as the Northeast Monsoon. The tropical air flowing out from the Pacific High Pressure comes to the Japan proper as the southerly tropical air and reaches the Philippines as the northeast trade wind. The SW Monsoon appears on the stage from April on even to November and December in the Philippines. Doubts may arise as to the exact propriety of the word “monsoon”, but in this paper we will use it with Deppermann to include all the air coming to the region apparently from the southern hemisphere.There are really such three air-masses in the equatorial or tropical region. Deppermann(1) named the front between the SW-Monsoon and the trade wind or the northers as the “Equatorial Front.” The front between the tropical air and the northers is naturally the polar front after J. Bjerknes.A'most all the typhoons originate at the Equatorial Front. They first travel westwards along the front, until they reach the “Dreimasseneck”(2), at which we find intense interaction between the SW-Monsoon, Tropical air and the Polar air. After a little beyond this point, they often recurve and travel to the northeast along the polar front. Very often they steadily travel to westwards beyond the said point along the Equatorial Front between the northers and the SW Monsoon.The location of the Pacific fronts is determined on the ground that the axis of the region of greatest cyclone frequency indicates the mean position of the front (Fig. 1). The smoothed isarithms on this map represent total typhonic frequency during the 5-year period ending 1936. These frequencies were tabulated for bimonthly intervals (September-October) and were plotted for each 2° square of latitude and longitude. The original data were obtained from the weather maps analysed by the Central Meteorological Observatory, Tôkyô, Japan. The marked relation between fronts and two types of typhoon's track, of which it often seems to be difficult to get a clear mental picture, is illustrated by Fig. 1 in quite satisfactory manners. Figure 2, depicting yearly air masses and fronts in the North Pacific, is a graphic representation of the said conclusions derived from examination of the maps of requency of typhoons.2) Typhoons in the North Pacific sometimes recurve in the vicinity of the tropic or a little beyond it During the recurving they increase in strength and their progressive movement slackens. After the recurving they rapidly travel eastwards but decreases in strength, Depressions in the North Pacific generally recurve in the vicinity of Aleutian Islands. During the recurving they increase in strength. After the recurving they die out in the stage of occlusion. Fig. 3 is based on the model employed by the author and illustrates the application of his theory, whose underlying principle is the Kinematical Analysis of the Field of Pressure(1).3) There are two classes of phenomena of föhn for which the aid of Ficker's theory must be invoked. On the southeastern side of the Japan proper (Pacific coasts), the föhn of relatively cold winds are observable in the colder half of the year during which the northwesterly monsoons prevail. On the northwestern side of the Japan proper, the föhn of very warm, dry winds are observable in summer during which the southerly monsoons prevail. By the usual theory of föhn, it can hardly be possible to explain the extreme hotness 40.8°C observed at the Yamagata Observatory on July 25, 1933. In order to discuss this phenomena, aerological materials on the windward side (Fig. 6) are carefully analysed. It is concluded that in the upper atmosphere a marked inversion had been observed in the layer which extends from 500 metres.

[学科分类] 大气科学