極東亜熱帯湿潤気候区の低気圧にともなう豪雨

Abstract

On June 27, 1972, torrential rains fell over the southwestern Kyushu, the western part of Japan, when a weak frontal depression passed to the north of Kyushu. The large-scale characteristics of heavy rainfalls in the Asian subtropical-humid region are represented through the case study on this heavy rainfall.Synoptic and subsynoptic-scale analyses indicate that 1) the heavy rainfalls occurred within the subtropical air mass to the south of the subtropical jet stream's axis; 2) destabilization of the stratification on the heavy rainfall area was not caused by the cold air intrusion aloft but mainly by the intrusion of the tropical air mass in the lower layer; 3) the extremely moist tropical air mass was transported toward the depression from the south along the western periphery of the Pacific subtropical anticyclone.We also give our attention on the differences between the large-scale features of the heavy rainfalls in the Asian subtropical-humid region and these of severe storms in the subtropical-humid region of U.S.A. In essence, the heavy rainfalls are the convective phenomena within the subtropical air mass occurred under the condition of the intrusion of tropical air, while the severe storms are those within the subtropical air mass occurred under the condition of strong cold advection aloft.