台湾地形对1011号台风“凡亚比”影响的数值试验

A numerical experiment for the effect of Taiwan island terrain on super typhoon Fanapi(1011)

利用WRF-ARW 3.2.1模式,对台湾岛地形对2010年第11号超强台风"凡亚比"的路径、降水及结构的影响进行了数值模拟和敏感性试验。结果表明:台风登陆台湾岛前,迎风坡地形低压作用使台风中心南落并出现逆时针打转;背风坡地形低压和台风西北侧台湾海峡出现弧状正涡度带,使台风进入台湾海峡时出现"V"型异常路径;台湾岛地形作用使台风西北侧水汽辐合和正涡度减小,而使其东侧、南侧水汽辐合和正涡度增加,台风出现西北弱、东南强的不对称结构和降水不均匀分布;台湾中部山脉地形对台风低层流场的阻挡抬升作用对台风降水具有明显的增幅作用,造成台湾岛降水分布呈南部、东部强而西北部弱的不对称分布。

Numerical simulations and sensitivity experiments for the effect of Taiwan island terrain on track, precipitation and structure of super typhoon Fanapi （1011） were performed with the WRF-ARW 3.2.1 model. The results indicate that owing to effect of the topographic low pressure at windward slope, the typhoon moved southward and had a motion in the counter-clockwise direction before it landed on the Taiwan island. The topographic low pressure at leeward slope and the bow-shaped positive vorticity zone in northwest side of the typhoon make it move in a V-type track when it was in the Taiwan Straits. The obstruct by Taiwan island terrain makes the water vapor convergence and the positive vorticity decreased in northwest side of the typhoon, but increased in east and south side of the typhoon. The typhoon presents an asymmetric structure of weak in northwest and strong in southeast in its intensity and an inhomogeneous distribute of precipitation. The Ter-rain effects of mountains in the central Taiwan regions on typhoon flow field in the low-level leads to increase of precipitation and an asym-metric precipitation distribution being strong in south and east and weak in northwest Taiwan regions.