doi:  10.3878/j.issn.1006-9895.1711.17135
台风Morakot(0908)过台湾岛缓慢西行成因分析

On the slow movement of Typhoon Morakot (0908) crossing Taiwan Island
摘要点击 2081  全文点击 257  投稿时间:2017-03-14  修订日期:2017-11-27
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基金:  国家重点基础研究发展计划(973计划)项目2015CB452804,国家自然科学基金项目41475055,41675044,科技基础性工作专项2013FY112400。,国家自然科学基金,国家重点基础研究发展计划
中文关键词:  台风  缓慢移动  诱生低压  非对称结构
英文关键词:  Typhoon  slow movement  terrain-induced low  asymmetric structure
           
作者中文名作者英文名单位
龚月婷GONG Yueting中国气象科学研究院灾害天气国家重点实验室
李英LI Ying中国气象科学研究院灾害天气国家重点实验室
高迎新GAO Yingxin北京市气象局
徐洪雄Xu hongxiong中国气象科学研究院
引用:龚月婷,李英,高迎新,徐洪雄.2018.台风Morakot(0908)过台湾岛缓慢西行成因分析[J].大气科学
Citation:GONG Yueting,LI Ying,GAO Yingxin,Xu hongxiong.2018.On the slow movement of Typhoon Morakot (0908) crossing Taiwan Island[J].Chinese Journal of Atmospheric Sciences (in Chinese)
中文摘要:
      0908号台风“莫拉克”(Morakot)在台湾岛引发了24h超过1000mm的强烈降水,与其缓慢西行过岛密切相关。本文利用NCEP - GFS 实时分析场资料(0.5°×0.5°)、我国台湾中央气象局台风资料库地面气压场资料和中尺度数值模式WRF模拟结果,分析了台风Morakot在台湾岛附近缓慢西行成因。结果表明,1)西太平洋副热带高压减弱东退、与台风“天鹅”(Goni,0907)的“藤原效应”是Morakot在台湾岛附近移速减慢的环境因素,而台风结构变化也是其缓慢过岛西行的一个主要原因。2)台风过岛过程中,由于地形作用,Morakot环流内诱生低压活跃,先后或同时出现在岛屿东西两侧,使台风环流出现非对称松散结构。3)在台湾岛西侧诱生低压中心取代东侧原台风中心形成不连续路径过程中,台风经历了低层环流从分裂到重组,正垂直涡度柱从垂直到倾斜再恢复垂直的变化过程。这是Morakot过台湾岛缓慢西行的一个重要原因。4)Morakot西行登岛过程中环境引导气流主要是偏南气流,而包含诱生低压的扰动引导气流则为偏东气流。扰动引导气流虽是小量,但其纬向分量占环境引导气流纬向分量的比率从7% 增至26%,较好地指示了Morakot的西行趋势,也说明地形诱生低压导致的台风结构变化是其过岛西行和缓慢移动的一个重要原因。
Abstract:
      The heavy 24-h rainfall over 1000mm in Taiwan, China caused by Typhoon Morakot (0908) is closely related to its slow moving speed. Using real-time NCEP - GFS global analysis data (0.5°×0.5°), synoptic charts of surface observations in Taiwan area from Central Weather Bureau (CWB) Typhoon Data Base and numerical simulation output from the Weather Research and Forecasting Model (WRF), the causes of the slow westward movement of Typhoon Morakot around Taiwan Island is investigated. Results show that the weakening and eastward withdrawing of the western Pacific subtropical high and the Fujiwara effect interacting with Typhoon Goni (0907) are the main environmental factors for Morakot’s slow movement. The structure change of Morakot is also an important cause resulting in its slow westward movement. It is found that the terrain of Taiwan Island could induce several lows within typhoon circulation to increase its asymmetry. The terrain-induced low developing on the west side of Central Mountain Range replaces the original Morakot center on the east side, resulting in a westward discrete track. During this process, Morakot structure experiences a complex change with its positive vertical vorticity column recovering vertical from tilting and its lower layer circulation re-organizing from splitting with a slower moving speed. The impact of these mesoscale vortexes on the environmental steering flow is further investigated using Barnes filter method. It is found that the mesoscale disturbance is favorable to increase the westward steering flow although as a small amount. However its percentage accounting for the total environmental steering flow increases from 7% to 26% when crossing Taiwan Island, indicating the important role of structure change related to terrain in Morakot’s slow westward movement.
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