The Structure of General Circulation over Continent of Asia in Summer

[摘要]  In this article, an analysis is made on the structure of the mean flow field at 5000, 10000 im one 20000 ft level in July over the continent of Asia during the year 1950-1955 and the mean wind contours at 200 mb over Asia for July and August, 1956. The vertical cross-sections of the mean flow and temperature fields along 75°E, 90°E, 105°E and 120°E for July and August, 1956 have been constructed. The three-dimensional structure of flow over continent of Asia is constituted of the following three basic currents: (1) the westerlies of middle latitudes,(2) the upper level tropical and subtropical easterlies, and (3) the south-westerly monsoon under the upper level tropical and subtropical easterlies. Moreover, the changes of the general circulation over Asia in the transitional period between that a leaping change of the general circulation over Asia occurs during this period. The upper level subtropical westerly jet-stream to the south of Himalaya retreated northward and a subtropical ridge was established over the latitude of Tibet, and over south Asia (to the south of 12°N) an high level easterly jet-stream India and the “Meiyu” (plum rain) season of the Yangtze Valley set in. The authors also found that the northward displacement of the rain belt is closely related to the northward retreat and the accompanying weakening in intensity of the westerlies over China main land.

[学科分类] 大气科学