梅雨季台灣地區平均雲頂溫度之時空分布特徵探討

Study on the Characteristics of Temporal and Spatial Distribution of Cloud Top Temperature over Taiwan Area during Mei-Yu Season

紀水上(Shui-Shang Chi) ； 陳泰然(George Tai-Jen Chen) ； 郭世昌(Shi-Chang Kuo)

《大氣科學》 26卷1期 (1998/03) Pp. 1-17

摘要

本文利用每小時GMS數據化紅外線資料及台灣西南部測站地面風場資料，探討梅雨期台灣與鄰近地區平均雲頂溫度之時空分布特徵與盛行風和局部環流及彼此間之交互作用。結果顯示，台灣西南部陸上對流於海風及╱或上坡風出現後開始發展，於下午發展成熟後向西南移動，或由對流下衝流與盛行風和海風產生局部輻合，激發新對流向盛行風上游發展。陸風與盛行風可於西南部海上產生局部輻合以激發對流，使西南部海上對流於夜間陸風發生後開始發展，並持續至次日清晨。平均雲頂溫度之南北和東西時間剖面分析顯示，對流發展呈現顯著的日夜變化，呈午後最強與清晨次強之雙高峰形式。白天對流於中央高山或西部山坡先行發展，之後西移進入西部沿海或由原對流之下衝流與盛行風和海風產生局部輻合使新對流向西發展。顯然局部環流與盛行風之交互作用以及海風或上坡風與地形之交互作用在激發對流發展扮演重要角色。

關鍵字

雲頂溫度 ； 日夜變化 ； 雙高峰 ； 局部輻合 ； 局部環流 ； 海風 ； 陸風

並列摘要

Hourly GMS digital IR data and the surface wind observations over southwestern Taiwan were used to study the characteristics of temporal and spatial distribution of the cloud top temperature. The relationship among the cloud top temperature, the prevailing wind, local circulations and their interactions were also investigated. Results show that the land convection over southwestern Taiwan began to develop right after the sea breeze and/or upslope wind started. Results suggested that the convective system either moved southwestwards in the late afternoon, or new convection was triggered by the local convergence presumably due to the interaction between the convective downdraft and the prevailing wind as well as the sea breeze and thus developed upstream. Local convergence induced over the sea due to the prevailing wind and the land breeze in the night time could trigger the convection. Therefore, the convection over the sea to the southwest Taiwan developed after the land breeze occurred and persisted until the next morning.Results of the north-south and east-west time cross-section revealed that the development of convection possessed double peaks. The primary peak occurred in the late afternoon, and the secondary peak occurred in the early morning. The daytime convection seemed to start over Central Mountain Range or its western slope. It then moved westwards to the western coast of Taiwan, or the new convection was triggered by the convergence due to downdraft of existing convection and the prevailing wind as well as the sea breeze and then developed upstream. Apparently, the interaction between the local circulations and prevailing winds along with the interaction between the sea breeze or upslope wind with topography played an important role on triggering the convection.

並列關鍵字

Cloud top temperature ； Diurnal variation ； Double peak ； Local convergence ； Local circulation ； Sea breeze ； Land breeze