2015年“东方之星”翻沉事件和2016年阜宁EF4级龙卷对流风暴环境条件、结构特征和机理  

Environmental Conditions, Structures, and Mechanisms of Convective Storms of 2015 “Oriental Star” Capsizing Event and 2016 Funing EF4 Tornado

作　　者：郑永光[1] 朱文剑 田付友 Zheng Yongguang;Zhu Wenjian;Tian Fuyou(National Meteorological Centre, China Meteorological Administraion, Beijing 100081)

机构地区：[1]国家气象中心,中国气象局,北京100081

出　　处：《气象科技进展》2018年第2期44-54,共11页Advances in Meteorological Science and Technology

基　　金：国家自然科学基金项目(41375051);国家重点研发计划(2017YFC1502003)

摘　　要：2015年"东方之星"翻沉事件(简称2015年事件)和2016年阜宁EF4级龙卷(简称2016年事件)都是极其罕见的极端强对流大风事件。利用多种观测资料、综合应用"配料法"的分析思路对比分析了两次事件的环流背景、环境条件、对流风暴的结构特征和地面大风与龙卷的形成机制。结果表明,两次事件虽然发生在有些类似的环流背景下,但环境条件存在很大差异。2015年事件对流层中层的显著干层使得大气具有较大下沉对流有效位能是有利于地面大风的重要环境条件,而0~6km垂直风切变强度则为中等;2016年事件则具备了有利于中气旋龙卷的所有有利环境条件。2015年对流风暴为一个主要伴随负地闪、质心低、最大反射率因子约50d Bz的β中尺度弓形线状对流系统;而产生2016年龙卷的则为一个主要伴随正地闪、质心高、最大反射率因子超过65d Bz的β中尺度经典超级单体对流风暴。2015年对流风暴存在多个微下击暴流区,约5km高度的中层附近存在强后侧入流区和中涡旋结构;而2016年超级单体风暴存在底高低于1km、自下向上、向东北方向倾斜的强中气旋和龙卷涡旋特征,以及钩状回波和回波悬垂等特征,并在高分辨率静止气象卫星可见光图像上有明显的旋转特征。2016年超级单体风暴冷出流与环境地表大气温度差小于4℃,显著弱于2015年对流风暴,这种不太强的下沉气流是该超级单体风暴能够产生龙卷的重要原因之一。The “Oriental Star” capsizing event in 2015 （Hereafter 2015 event） and the Funing EF4 tornado event in 2016 （Hereafter 2016 event） are extremely rare damaging wind events caused by severe convective storms. Based on multi-source data, this paper applied the “ingredients-based” method to compare the atmospheric circulation backgrounds, environmental conditions, structure and mechanisms between these two events of convective storms. Results show that both these events occurred in partially similar circulation backgrounds, but there are considerable differences in the environmental conditions. For the 2015 event, the most important environmental conditions conducive to high surface winds are the signifcantly dry layer in the middle troposphere that makes a larger downdraft convective available potential energy, and 0-6 km vertical wind shear has only a medium intensity. For the 2016 event, all the environmental conditions are very favorable for mesocyclone tornado. The 2015 convective storm was a meso-β scale bow-shaped quasi-linear convective system with significant negative lightning flash, low mass center of refectivity, and about 50 dBz of the maximum refectivity. However, the 2016 convective storm was a meso-β scale classical supercell with signifcant positive lightning fash, high mass center of refectivity, and about 65 dBz of the maximum refectivity. There were multiple shallow downbursts in the low troposphere, and strong rear infows and a mesovortex at about 5 km altitude in 2015 convective storm. Nevertheless, the 2016 supercell storm had a strong mesocyclone with base height less than 1 km and tilting northeastwards from bottom to top, and a tornadic vortex signature, and hook echo and overhang echo signatures; besides, it appeared rotating on the high-resolution visible images observed from geostationary meteorological satellites. The surface air temperature differences between the cold outfow of the 2016 supercell storm and the environment was less than 4℃, and they were weaker than

关 键 词：龙卷 极端大风 下击暴流 中气旋 

分 类 号：P445[天文地球—大气科学及气象学]