TAMEX期間高低層噴流的耦合情形

The Coupling of Upper-Level and Low-Level Jet Streaks during TAMEX Period

蔡清彥(Ching-Yen Tsay)

《大氣科學》 19卷1期 (1991/03) Pp. 67-87

摘要

本文選擇1987年TAMEX期間IOP2 IOP3a及IOP8三個梅雨個案，分析高層噴流與低層噴流的耦合情形，並討論所伴隨之垂直環流情形，以及整體環流對台灣地區降雨的影響。綜合Tsay and Kau（1989）及本文的研究，我們發現在台灣地區的梅雨期間有兩類整體環流可能發生。第一類整體環流包括高層噴流，位於高層噴流（Upper-Level Jet，簡稱ULJ）入區南方，並平行之低層噴流（Low-Level Jet，簡稱LLJ），位於兩噴流間之上升運動及伴隨之兩胞環流。當此類整體環流東移，LLJ抵達台灣北端時將造成台灣地區之降雨。第二類整體環流則有兩支高層噴流，南支ULJ與LLJ成X形相交，在交點北方則有上升運動並伴隨熱力間接環流。當此類整體環流東移後，南支ULJ將與北支ULJ合併，此類整體環流就將演變為第一類整體環流。若能在抵達台灣地區前演變成為完整之第一類整體環流系統，則仍可帶給台灣地區大雨，否則將成為少雨的梅雨個案。

關鍵字

高層噴流 ； 低層噴流 ； 梅雨

並列摘要

Three cases including IOP2 IOP3a and IOP8 in 1987 TAMEX period have been selected for this study. The coupling of the upper-level and low-level jet streaks and the accompanying vertical circulation system have been analyzed. The influence of the overall circulation system to the precipitation in Taiwan were then discussed.According to Tsay and Kau (1989) and present study, we find that two kinds of circulation systems may occur during Taiwan Mei-yu period. The first kind of circulation system includes upper-level jet (ULJ). Low-level jet (LLJ) paralleled and located to the south of entrance portion of ULJ, upward motions in the area between these two jet streaks and accompanying two-cell vertical circulations. This kind of circulation has been discussed by Chen (1982). The total system will move eastward after developed in southeast mainland China. Precipitation in Taiwan will start when LLJ reaches the northern tip of Taiwan island.The second kind of circulation system will have two upper-level jets. The southern ULJ is oriented in WNW to ESE direction, while LLJ is oriented in SW to NE direction. The southern ULJ and LLJ form an X-cross. Upward motion is located to the north of the crossing point. A direct circulation cell is accompanied with the upward motion. This kind of circulation system is similar to the system in north America discussed by Uccellini and Johnson (1979).The second kind of circulation system will also move eastward. After the center of upward motion moving to the east of 115°E, the southern ULJ will have sudden northward jump and merge with the northern ULJ. The circulation system will change to the pattern of the first kind of circulation system. If the development of this new first kind of circulation pattern is completed before arriving Taiwan, Taiwan will have heavy rainfall. Otherwise it will be a less rainfall case.

並列關鍵字

Upper-level Jet ； Low-level Jet ； TAMEX ； Mei-Yu