风切变

Multi tool use
風切變(wind shear),又稱風剪,是指大氣中不同兩點之間的風速或風向的劇烈變化。
概要
根据两点高度之间的差异,风切变可分为水平和垂直两大类。
垂直风切变
是指垂直於地表方向上風速或風向隨高度的劇烈變化,強烈的垂直风切变的存在會對橋樑、高層建築、航空飛行等造成強烈的破壞作用,可造成橋樑樓房坍塌、飛機墜毀等惡性事故,給人類生活造成嚴重影響。
水平风切变
則指與地面平行的方向上風向的急速轉變。
影響
人類
风切变對航空飛行的危害極大。在起飛和降落的過程中,由於飛行速度低,风切变能夠對航空器空速產生很大的影響,致使航空器的姿態和高度發生突然變化,在低高度上其結果有時是災難性的。
1985年,美國達美航空191號班機於達拉斯-沃斯堡國際機場墜毀,造成137人死亡。從此,风切变被當作一項國際課題開始研究。據美國博爾德全國大氣研究中心的負責人科爾曼說,1985年以後,美國所有的飛機都安裝了风切变檢測儀。加拿大1990年代開始安裝。
2009年3月23日,联邦快递80号班机在日本成田国际机场降落时,因风切变坠毁,2名驾驶员遇难。
自然
垂直风切变強烈,除了影響令熱帶氣旋難以生成外,亦可迅速破壞成熟的熱帶氣旋,甚至令其消散,可謂是熱帶氣旋的大敵。
在東南太平洋和南大西洋地區,即南美洲東面和西面的海域,因該兩區皆有強烈的垂直风切变,使得熱帶氣旋無法在當地區域形成。也因如此,有不少寒流都可以在該兩區的低緯度地區容易產生,使南美洲北部和非洲西南部的氣溫也相對地低。
外部連結
一個監察垂直風切變的網站
相關條目
微下擊暴流 - 以順風方向吹流經飛行器的局部性下沉氣流,使飛行器升力大減
- 熱帶氣旋
- 溫帶氣旋
- 蒲福氏風級
- 風能
- 風
- 中華航空642號班機
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