Dynamic Climatology of Atmospheric Circulation over East Asia centered in Japa n

• Published in: Papers in Meteorology and Geophysics Vol. 19; no. 1; pp. 1 - 68
• Main Author: Asakura, Tadashi
• Format: Journal Article
• Language: English; Japanese
• Published: Japan Meteorological Agency / Meteorological Research Institute 01.01.1968
• Subjects: Blocking; Climatology; Deformation; East Asia; Rain; Ridges; Seasons; Summer; INW, Okhotsk Sea; Japan; China, People's Rep., Xizang, Tibetan Plateau; ISW, India; North America; ANE, Europe; INW, Japan
• ISSN: 0031-126X; 1880-6643
• DOI: 10.2467/mripapers1950.19.1_1

The present paper studies; (i) the relationship between the weather in Japan and the upper-air circulations in East Asia which are classified into six flo w types (Part I) (ii) the syn optic processes and causes of the formation of blocking flow pattern in East Asia (part II) (iii) the causes of Baiu in East Asia relating to the atmospheric circulation and the heat source near the Tibetan Plateau (part III) The upper-air flow patterns in East Asia are classified into s ix kinds. They are high index zonal flow, trough flow, summer flow types (which bring about high temperature in Japan) and low index zonal flow, wave flow, blocking flow types (which bring about low temperature in Japan). In general, high index zonal flow, trough flow and blocking flow types bring about much rain, wave flow and low index zonal flow types little rain in Japan. And abnormal weathers in Japan are generally accompanied with the blocking flow pattern in East Asia. Next, the synoptic processes that for m a blocking flow pattern in the Shfirin and winter seasons are analysed. The former is responsible for the rainy season in Japan in early autum and the latter for the cold NWmonsoon. A blocking flow pattern in the Shtirin season is initiated by the deformation of westerly flow which is given by a typhoon invasion into a westerly flow. This deformation is transferred downstream with a group velocity, resulting in the splitting of the westerly flow into two branches when the Shtirin season starts. Another blocking flow type in winter is caused by a large-scale heat exchange which is initiated by the development of a ridge over the Atlantic Ocean. With the development of this ridge, the polar air breaks out to Europe and America, resulting in the reinforcement of the ridges over the Asiatic Continent and the west coast of North America. These two ridges progress toward each other and finally fuse into one strong ridge, forming a blocking flow pattern in East Asia. In early summer, Japan is visited by the Baiu season with a blocking flow pattern. The beginning of this season and the SW monsoon in India have a close parallelism, and the stronger the monsoon low the stronger the Okhotsk sea high. Furthermore, the stronger the anticyclone over the Tibetan Plateau in early summer, the more predominant the blocking flow in East Asia. These statistical relationships are reexamined by anumerical experiment incorporating the effect of the atmospheric hea t source and sink in early summer.