不同性質梅雨鋒面系統之大尺度環流特徵

Variations of Large-Scale Circulations Associated with Mei-Yu Fronts of Different Types

陳泰然(George Tai-Jen Chen) ； 周仲島(Ben Jong-Dao Jou)

《大氣科學》 16卷3期 (1988/09) Pp. 309-322

摘要

本文針對東亞梅雨之鋒面系統與大尺度環流進行觀測資料之診斷分析研究，利用1981~1984年5~6月綜觀天氣圖、衛星雲圖與NCAR網格點資料，以分析梅雨鋒面之大尺度環流結構與不同性質梅雨鋒面系統間之大尺度環流差異。結果發現，決定個別鋒面系統位置偏北或偏南之因子為環流強度與位置而非季節，偏南與偏北鋒面分別由中緯與低緯環流主宰。對流活躍之條件為低對流層源自孟加拉灣之較強西南氣流，較不活躍者則伴隨太平洋高壓環流之東南或西南氣流。此外發現鋒面低壓穩定者中緯均有阻塞，不穩定者則大部分無阻塞；鋒面東西走向者亦均有阻塞且太平洋高壓與季風低壓均較強，東北－西南走向者則無此特徵。

關鍵字

梅雨鋒面 ； 西南氣流 ； 阻塞

並列摘要

A diagnostic study of Mei-Yu frontal systems and large-scale circulations during the East Asia Mei-Yu season was carried out. Synoptic charts. GMS IR pictures and NCAR grid-point data in May-June 1981-1984 were used to study the similarities and the differences of large-scale circulations for various types of frontal systems.Results showed that the primary factor for determining the more northern or more southern position of an individual frontal system was the intensity and location of large-scale circulations rather than the season. The more northern location and the more southern location of a frontal system was primarily controlled by the low-latitude and mid-latitude circulations, respectively. It was found that the low-tropospheric air responsible for more the actively convective cases was the stronger southwesterlies originated from the Bay of Bengal. For the inactive convection case, the low-troposphere was dominated by the southeasterlies or southwesterlies of the subtropical Pacific high. The mid-latitude circulations were quite different for the frontal systems with stable and unstable frontal waves. Blocking was observed for all the stable cases, while no blocking was observed for most of the unstable cases. Existence of a blocking and a stronger Pacific high and a stronger monsoon low were observed for all the E-W oriented frontal systems. This was not observed for the NE-SW oriented ones.

並列關鍵字

Mei-Yu front ； southwesterly flow ； blocking