A Numerical Study of the Terrain Effects on a Squall Line

地形對颮線影響的數值研究

陳景森(Ching-Sen Chen)

《Terrestrial, Atmospheric and Oceanic Sciences》 1卷1期 (1990/03) Pp. 73-90

摘要

觀測顯示有一些降水系統如颮線從台灣海峽東移到台灣山區，會受到地形的影響而減低其強度，然後消散。顯然地形效應相當重要，吾人利用一有地形座標的雲雨模式來探討地形對颮線的影響，在模式內，山頂假設1或2公里高，模式中的颮線在平原產生後，能繼續發展。這是因為在颮線前綠能繼續不斷地產生新生對流併入颮線，維持颮線的強度，但是等到颮線進入山區，移動速度減慢，而且強度減弱，減弱的原因，是由於新生對流變弱，而新生對流的強度衰退，是由於在山區流入颮線的水汔減少。另外模擬結果顯示山的高度愈高，抑制颮線發展的效應也愈大。

並列摘要

Observations indicate that some squall line systems moving from the Taiwan Strait towards the mountains would decrease in intensity and dissipate. Obviously the terrain effects on the squall lines are very important. A two-dimensional terrain following coordinated cloud model was used to study geographical effects on a squall line. In the model the mountain peak was assumed to be 1 or 2 km in height with the squall line forming over the plain area and propagating towards the mountains. In the plain area new convection continually formed on the forward side of the squall line so that the squall line could maintain itself. When the squall line moved over mountainous areas it slowed down and began decreasing its intensity due to the weakness of new convection. The decrease in intensity resulted from less moisture flowing into the squall line at the higher altitude. The terrain effect on the restriction of the development of the squall line was more evident the higher the mountain.