- 作者： 陳泰然; 周仲島; 李瑞麟
- 作者服務機構： 國立臺灣大學大氣科學研究所
- 中文摘要： 本文利用1975－1984年臺灣梅雨期（5月15日－6月15日）NCAR客觀分析之網格點資料及天氣圖分析，研究東亞長期平均之大尺度環流形式與鋒面活動之特徵。利用觀測風計算氣流函數及速度位，以分析東亞旋轉風場與輻散風場之分佈。 梅雨鋒生區與先前研究結果一致，發生於35°N以南之華中／華南。鋒面南伸及緩慢南移，主要顯係由中緯環流系統及華南地形阻擋效應主宰。臺灣梅雨期，西伯利亞東部有一微弱阻塞且北印度季風環流系統已經建立。同時，東亞主槽及西太平洋高壓脊之弦度及位置均屬5月至6月之過渡型。 季風低壓與梅雨鋒面區之對流產生之高層輻散外流，顯然構成東亞兩個區域性哈得里胞之高層支流。由梅雨區輻散分流軸向中緯之高層顯著輻散流顯示，副熱帶梅雨活動可能影響中緯環流系統。
- 英文摘要：
Long-term means of large-scale circulation patterns and corresponding frontal events over East
Asia during Taiwan's Mei-Yu season (May 15 - June 15) of 1975-1984 were examined by using NCAR
objectively-analyzed grid point data and synoptic weather charts. Streamfunction and velocity potential
were calculated by using observed winds to depict the rotational and divergent components of the winds
over East Asia.
In consistency with previous studies, it is found that the genesis area of the Mei-Yu front is located
to the south of 35?N in subtropical China. Also, the slowness of southward movement and the southward
penetration of the Mei-Yu front seem to be mostly controlled by the midlatitude circulation systems and
the hindrance effect of terrain over subtropical China. During Taiwan's Mei-Yu season, a weak blocking
over eastern Siberia and a well-established monsoon system over northern India are found in the long-term
time-mean circulations. Meanwhile, the intensity and position for both the East Asian coast major trough
and the western Pacific subtropical high show a transition type between the intensity and position in May
and June.
The upper-level divergent outflows produced by the convections over the monsoon low and the Mei-
Yu frontal area apparently constitute the upper-level branches of the two local Hadley circulations over
East Asia. The pronounced upper-level divergent outflows from the diffluent axis over the Mei-Yu area to
the midlatitudes suggest that the Mei-Yu activity in the subtropical area may play some roles in affecting
midlatitude circulation systems.
s - 中文關鍵字： large-scale circulation; Mei-Yu front; monsoon circulation system; divergent outflow
- 英文關鍵字： --
