气象   2020, Vol. 46 Issue (1): 98-107.  DOI: 10.7519/j.issn.1000-0526.2020.01.010

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WANG Kai, LIANG Yitong, LIU Min, 2020. Field Investigation and Analysis of Wind Disaster and Estimation of Disaster Wind Speed of the Capsizing Accident of Cruise Ship "Oriental Star"[J]. Meteorological Monthly, 46(1): 98-107. DOI: 10.7519/j.issn.1000-0526.2020.01.010.
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2018年8月1日收稿
2019年3月27日收修定稿
“东方之星”翻沉事件风灾现场调查分析与致灾风速估算

Field Investigation and Analysis of Wind Disaster and Estimation of Disaster Wind Speed of the Capsizing Accident of Cruise Ship "Oriental Star"
WANG Kai, LIANG Yitong, LIU Min
Wuhan Regional Climate Center, Wuhan 430074
Abstract: Take the capsizing accident of cruise ship "Oriental Star" as an example. The analysis of the previous study and the field investigation shows that on 1 June 2015, from 21:00 BT to 21:15 BT, severe weather such as thunderstorms, strong winds, heavy rains and tornadoes hit the investigation area. The duration was about 30 minutes. The disaster process was characterized by the most severe windstorms, with spatial discontinuities and small scales. The survey results show that there were vertical shear and horizontal shear in the wind field along the Yangtze River in the accident area. Radar monitoring showed that the mesocyclone moved from the west bank of the Yangtze River to the east bank, having vortex cha-racteristics. This process was mainly based on windstorms. The severely affected area was concentrated within the range 8 km north of the accident, the Sitai village on the east bank of the Yangtze River, which is about 4 km away from the accident, was the most seriously affected, This region had strong wind shear and signs of divergence.The main affected objects were trees, crops, houses, boats, etc., causing the most damage to trees, a total of 31 disaster sites, accounting for 72.1% of the total survey sites. In the accident area, the trees on the west bank of the Yangtze River were broken or the direction of lodging was mainly southeastward, the trees on the east bank was mainly eastward. So, the direction of the trees dumping was clearly consistent. However, there were horizontal shears on both sides of the Yangtze Ri-ver, and the wind direction was deflected by nearly 90°. The quantitative evaluation method of wind disaster was explored by combining actual disaster with mechanical model. Take the severely affected poplar as an example, the anti-overturning moment calculation method was used to estimate the disaster rate. The results show that strong wind was one of the important causes of the accident. The wind speed of the di-saster was 28.7 m·s-1, reaching Grade 10 or above.
Key words: field investigation    disaster wind speed    estimation

20世纪以来，中国大陆共发生三起大型海难，分别为，“江亚号”沉没事件、“大舜号”沉没事件，以及“东方之星”翻沉事件。“东方之星”翻沉事件是长江航运史上影响最大的一次事件，发生在2015年6月1日21：30左右，重庆东方轮船公司所属“东方之星”游轮上行至长江水域湖北荆州市监利县大马洲水道44号过河标水域处翻沉，导致442人遇难。6月2—14日期间，湖北省气象局多次派出调查组，联合中国气象局调查组赴监利县、岳阳市等地在辖区长江两岸开展实地调查。与郑永光等(2016a)通过现场天气调查分析并结合其他气象观测资料来揭示此次导致大风天气的原因和大气运动的复杂性以及多尺度性的调查目的不同，本文旨在从具体灾情出发，通过前期研判、影像拍摄、外围走访等手段确定大风天气的发生时间和地点、具体灾情和行经路径等，并结合个例分析，估算致灾风速，还原灾情实况；通过与郑永光等(2016a)的调查结果比较，验证该估算方法的准确性，为缺少实测数据的地区开展风灾定量化评估提供参考。

1 事件发生天气概况

2 事件调查情况 2.1 调查时间

2015年6月2—11日先后3次开展现场调查，详见表 1

2.2 调查范围

 图 1 调查区域基本情况 (RG为区域的英文缩写，数字为序号) Fig. 1 Basic situation of the survey area (RG: the region, numbers: serial numbers)

2.3 调查结果

 图 2 区域1与区域2调查范围及灾情基本情况 (箭头长短代表受灾体与调查点中心位置的距离，根据基准长度按比例放大，与比例尺无关，下同) Fig. 2 Survey scope and basic situation of disaster in Area 1 and Area 2 (Length of the arrow represents the distance between the disaster victim and the center of investigation point; length of the arrow is scaled up according to the reference length, regardless of the scale, the following is the same)

 图 3 区域3调查范围及灾情基本情况 Fig. 3 Survey scope and basic situation of disaster in Area 3

 图 4 区域4调查范围及灾情基本情况 Fig. 4 Survey scope and basic situation of disaster in Area 4

 图 5 2#(a)、34#~37#(b)、14#(c)和7#(d)调查点区域内农田、林地倒伏方向 Fig. 5 The lodging direction of farmland and woodland in the areas (a) 2# survey point, (b) 34#-37# survey point, (c) 14# survey point, (d) 7# survey point

 图 6 根据中气旋移动轨迹和现场灾情调查结果还原的事发过程地面风场实况 Fig. 6 Restoring the ground wind field during the accident with small and medium-scale cyclone movement trajectory and the results of the on-site disaster investigation
3 致灾风速的估算方法 3.1 受灾体基本情况

3.2 致灾风速估算

 图 7 抗倾覆估算示意图 Fig. 7 Anti-overturning estimation
 $M_{o}=W P \cdot S \cdot C F \cdot\left(H_{0}-H_{1} / 2-H_{2}\right)$ (1)

 $M_{a}=\tau \cdot 2 R \cdot D \cdot\left(D / 2+H_{2}\right)$ (2)

 $W P=0.5 \rho v^{2}$ (3)

Mo=Ma时，树木受力平衡，当Mo>Ma时，树木在风力作用下将会折断，将式(3)带入式(1)、(2)中，即得临界致灾风速Vc

 $V_{c}=\sqrt{\frac{2 \cdot \tau \cdot 2 R \cdot D \cdot\left(D / 2+H_{2}\right)}{\rho \cdot S \cdot C F \cdot\left(H_{0}-H_{1} / 2-H_{2}\right)}}$ (4)

 图 8 风速随水平夹角变化曲线 Fig. 8 Wind speed curve with horizontal angle
4 结论

“东方之星”翻沉事件发生区域内存在强对流天气系统，导致事发区域内出现雷暴、大风、暴雨等灾害性天气。

(1) 在事发地点半径12 km范围内开展现场调查，发现42处受灾点，调查结果表明：事发区域长江东岸受灾更为严重，其中顺星村、老台深水码头等地受风灾影响最重。沿江两岸风场同时存在垂直切变和水平切变，近地面西岸以偏西风为主，受河道、植被等下垫面影响，过江至东岸转北，变为西南风，局地存在辐散迹象。

(2) 现场调查显示受灾点分布分散，基本出现在雷达探测到的天气系统移动路径上，受灾点与其移动中心距离在1~3 km，且过境历时不足30 min，由此显示风灾具有空间分布不连续和小尺度的特征。

(3) 72.1%受灾点以杨树为主, 强风是树木倒伏或折断的主要原因，伴随强降水影响，渍涝严重，使得压弯、倒伏甚至折断现象更易发生。以杨树为研究对象，估算致灾风速，结果显示，致灾风速为28.7 m·s-1，即风力等级10级以上，与郑永光等(2016a)的调查结果基本吻合。由此可见，强风是造成此次事件的重要原因之一。