海風環流與陸地對流邊界層交互影響之數值研究

A Numerical Study on Sea Breeze and Its Interaction with Inland Boundary-layer Large Eddies

許武榮(Wu-Ron Hsu) ； 侯昭平(Jou-Ping Hou)

《大氣科學》 25卷3期 (1997/09) Pp. 397-418

摘要

海風環流與陸地邊界層之間的交互影響往往是十分顯著的，白天陸地邊界層的發展在海岸地區引發了海風環流，海風環流向內陸伸展時又改變了陸地邊界層的結構，同時海風鋒面在遭遇陸地邊界層內的對流胞時，也因為此兩種不同尺度運動交互作用而產生週期性的變化。本研究以一非靜力，高解析度模式探討此一交互影響過程。本研究所模擬的海風環流相當完整，並且存在著海風風速較強，厚度較薄，且集中在低層，而迴流風速較弱，但厚度較深厚的特性，和一般觀測相符。對流邊界層內大渦流的尺度大小也和實際觀測相當接近。模擬結果顯示了海風冷平流效應是抑制陸上對流的主要機制，也指出海風鋒面強度變化的週期恰為海風鋒面移行通過一內陸對流胞所需的時間。

關鍵字

海風 ； 對流邊界層 ； 海風鋒面 ； 大渦流模擬

並列摘要

Sea breezes are triggered by the convective boundary layer developed over coastal areas during the day. The horizontal spatial scale of the circulation is on the order of 10 km while the scale of the dominant large eddies inside the convective boundary layer over land is about 1km. When sea breeze penetrates inland, it collides with the large eddies and the structures of the two systems of different spatial scale change. The effect of cold advection brought by sea breeze suppresses the thermal convection over land, while the leading edge of the sea breeze circulation undulates due to interaction with the large eddies.We use a numerical model to examine this phenomenon. The model is two-dimensional and non-hydrostatic. It is free of artificial smoothing commonly used in numerical models and can still maintain numerical stability. The results show consistency with observations as regards to structures of both sea breeze and inland boundary layer. Our study demonstrates the importance of the advection process and explains the periodic behavior of the intensity of sea breeze fronts.

並列關鍵字

Sea breeze ； Convective boundary layer ； Sea breeze front ； Large-eddy simulation