Air Mas_??_es of Japan

[摘要] This memoir is essentially a sequel to one which I published recently in this journal with the same title. The following articles are studied:-(1) Atmospheric cross sections. A picture of atmospheric conditions in the vertical is urgently needed to supplement the present practice of representing the separate aerological soundin_??_s individually on one forms of diagrams. For such a cross section we choose a line, along which there lies a maximum number of airplane stations, as the base line i.e., the line of intersection of the vertical plane with the ground surface. In the long east-west section, we have Kasumigaura, Tatikawa, Yôkaichi, Oomura and Nanking. As for example, we illustrated the atmospheric cross section of the modified polar continental air mass, which los_??_s its original col'ness and dryness in the lower layers and is usually characterised by marked inversions, probably due to subsidence, above which the accumulated pollution and moisture cannot rise. The surfaces of subsidence inversion are extensive domes which may at times re_??_ch beyond 4 km level and often practically intersect the ground surf_??_ce along their pberiphery in rear of the polar continental air mass.(11) Atmospheric turbidity. In Fig. 10, the turbiditiesfor Ootomari, Zinsen, Morioka, Siomisaki, Hôkotô, Ogasawara, and Palao have been arranged. At all stations the polar continental air has the lowest turbidity but the turbidity increases rapidly as the polar air proceeds to the south-wards. And at all stations the tropical maritime air has the highest turbidity and the turbidity is nearly constant everywhere. These results are in agreement with our knowledge concerning the source regions and vertical structure of the air masses.Again the all stations show a seasonal trend in turbidity. The polar air has the lowest turbidity in the winter and highest turbidity in early spring, probably due to originating and moving over comparatively bared ground surface regions.(111) Potential gradient (Atmospheric electricity.) The polar continental air has generally higher potential gradient and the maritime air lower potential gradient. But the po_??_ential gradient show a marked seasonal change, so that the above conclusion can not be applied for indivisinl cases. It is found that the polar continental air has the highest potential gradient in winter, during which the NW-ly monsoons prevail over the Japan proper. And the maritime air has the highest potential gradient in summer, during which the tropical maritime air masses prevail over the Japan proper.Generally the potential gradients observed show a gradual increase as a front or a cyclone passes away, corresponding to the transformation othe air mass type from the fresh one to the mof dified one. This phenomena is remarkable in the colder half of the year. As the Polar continental air is modified, it is characterized by marked inversions below which the pollution and moisture is accumulated. Probably the gradual increase of the potential gradient is due to the existence of such haze layer.

[学科分类] 大气科学