Environmental and External Factors in the Genesis of Tropical Cyclone Nargis in April 2008 over the Bay of Bengal
Environmental and External Factors in the Genesis of Tropical Cyclone Nargis in April 2008 over the Bay of Bengal
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DOI：
10.2151/jmsj.2010-310
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发表时间：
2010-06
影响因子：
3.1
通讯作者：
S. Yokoi;Y. Takayabu
中科院分区：
文献类型：
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作者：
S. Yokoi;Y. Takayabu
2008 年 4 月下旬，热带气旋纳尔吉斯在孟加拉湾 (BoB) 上空产生，对缅甸沿海地区造成了严重破坏。本研究揭示了其成因的环境和外部因素。发现成因点周围的大范围环境条件普遍有利于气旋发生。对流层低层相对涡度呈正值，水平风垂直切变较弱，这是2008年4月气候学中所没有的显着特征。正如气候学中一样，海面温度和大气热力学剖面也有利于气旋发生。直到形成前六天，对流层中层的湿度都非常低且不利；似乎引发成因的大气扰动是吹入成因点的对流层低层东风涌流。与活跃对流相关的浪涌顶部的水平辐合被认为是触发气旋发生的外部强迫辐合。此外，活跃的对流似乎有助于对对流层中部湿度的预处理。这次东风潮与欧亚大陆东部沿海地区的寒潮有关，是4月份寒潮的典型特征。
Tropical cyclone Nargis was generated over the Bay of Bengal (BoB) in late April 2008, and it devastated the coastal area of Myanmar. This study reveals the environmental and external factors in its genesis.It is found that large-scale environmental conditions around the genesis point were generally favorable for cyclogenesis. Positive lower-tropospheric relative vorticity and the weak vertical shear of horizontal wind were observed, which were distinctive features of April 2008 that are not seen in April climatology. Sea surface temperature and atmospheric thermodynamic profile were also favorable for cyclogenesis, as in climatology. Mid-tropospheric humidity was significantly low and unfavorable until six days before the genesis; however, it increased abruptly to become favorable just before the genesis.The atmospheric disturbance that seemed to trigger the genesis was lower-tropospheric easterly surge blowing into the genesis point. Horizontal convergence at the head of the surge associated with active convection was considered as an External Forced Convergence that triggered cyclogenesis. In addition, the active convection seemed to contribute to the preconditioning of mid-tropospheric humidity. The easterly surge was associated with a cold surge in the eastern coastal area of the Eurasian continent, which is a typical feature of cold surges in April.