杨波,孙继松,刘鑫华. 2019. 两类不同风灾个例超级单体特征对比分析[J]. 气象学报, (0):-, doi:10.11676/qxxb2019.021
两类不同风灾个例超级单体特征对比分析
Comparative analyses of two supercells with different types of disastrously convective winds
投稿时间:2018-04-17  修订日期:2018-07-10
DOI:10.11676/qxxb2019.021
中文关键词:  大风灾害  超级单体 龙卷  下击暴流
英文关键词:disastrously  convective wind, supercell, tornado, downburst
基金项目:公益性行业(气象)科研项目(GYHY201506006),国家科技支撑计划项目(2015BAC03B04),国家重点研发计划(2017YFC1502003)
作者单位E-mail
杨波 国家气象中心 yangbo7625@163.com 
孙继松 国家气象中心 sunjs_0314@sina.com 
刘鑫华 国家气象中心 liuxh@cma.gov.cn 
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中文摘要:
      采用分钟级加密自动站,盐城、淮安和岳阳、荆州雷达数据,以及ECMWF高分辨率的ERA-Interim全球再分析数据,对比分析了2016年6月23日江苏阜宁龙卷灾害和2015年6月1日湖北监利下击暴流大风灾害的环境特征与超级单体的结构特征。结果表明:(1)两次强对流大风灾害发生在相似的低空环流背景下:风灾发生在低空急流出口区左侧的暖区内、850hPa低涡中心东侧6-7个经距的位置;环境大气的对流有效位能大于2000J/kg。但是风灾的类型不同,江苏阜宁大风灾害主要由超级单体龙卷造成,监利“东方之星”沉船事故主要是超级单体触发的下击暴流造成。短时强降水中心与风灾中心的相对位置不同:阜宁龙卷移动方向的左侧伴随着最强短时强降水;湖北监利沉船事件发生期间,风灾中心与短时强降水中心基本重合。鉴于不同性质的对流大风位置与超级单体母体的中心位置对应关系上存在差异,通过比较地面观测的瞬时大风与瞬时强降水中心的相对位置可能有助于区分强对流大风的性质。(2)环境垂直切变强度对对流风暴结构、发展、维持有重要影响:阜宁龙卷发生时,其上空0-6km垂直风切变达4×10-3 /s,超级单体有明显的向前倾斜结构,形成有界弱回波区;而监利强对流沉船位置0-6km垂直风切变只有2.3×10-3/s左右,风暴单体中的上升气流近乎于垂直。阜宁超级单体中气旋,首先出现在0-1.5km垂直风切变和0-3km风暴相对螺旋度带状大值区,在向抬升凝结高度更低的环境移动过程中,其底部不断下降,形成龙卷;而在监利沉船区,中低层风切变和风暴相对螺旋度相对要弱得多,对应风暴单体中的中气旋强度、持续性较弱,中气旋底部高度维持在1.6km左右。(3)环境湿度垂直结构特征不同可能是风暴单体形成不同类型灾害大风的重要环境因子。监利下击暴流造成的风灾发生时,在地面气温迅速下降过程中,气压变化呈现快速跳升又快速下降的“尖锥”形,气压峰值比降水峰值提前4分钟出现。它与对流层中高层环境大气中较为深厚的干空气卷入对流风暴中造成水物质强烈蒸发冷却过程有关。而阜宁风灾过程中,环境大气中层仅存在非常浅薄的干层,加之低层较为深厚的饱和大气环境,对应的地面冷池效应相对较弱。
英文摘要:
      Surface data with minute-resolution from automatic weather stations, weather radar data from Yancheng, Huaian, Yueyang and Jingzhou and ECMWF ERA-Interim global high resolution reanalysis data are used in this study. The characteristics of the circulation environment and the structure of two supercells are comparative analyzed. One supercell induced a tornado on 23th June 2016 and the other triggered downburst on 1st June 2015. The results are as follows. 1) The convective disasters occur in similar circulation environment. The supercells with disastrously convective winds appeared on the east side of the 850hPa low vortex and the left warm zone of low level jet. The distance between the center of low vortex and disaster area is about 600 to 700 km. There is also a small difference in the CAPE(more than 2000J/kg ). However, their features of the wind disaster are different, frightful disaster in Funing is mainly caused by tornado, and the accident of the "Eastern Star" on the Yangtze River is directly connected with downburst. The relative positions between maximum flash precipitation and windy disaster are different during the two convective activities. The maximum flash heavy precipitation,corresponding with supercell center, is on the left side of the moving direction of the Funing tornado. The ship capsizing accident is located at center of heavy precipitation during the severe convective weather. The relative position of the wind disaster against the instantaneous strong precipitation center is favorable to distinguishing downburst or tornado caused by supercell. 2) The vertical wind shear of the environment has an important influence on the structure, development and maintenance of convective storm. The environmental vertical wind shear of 0-6 km reached 24 m/s just before Funing tornado. The structure of the supercell is tilt forward with height, corresponding to a strong inclined updraft and bounded weak echo region (BWER). However, the environmental vertical wind shear is only about 14m/s in Jianli, and the updraft of the storm cell is almost vertical. Before the Funing tornado happened, the supercell with mesocyclone was first monitored in northwest of Jiangshu province, corresponding to environment with stronger vertical wind shear under 1.5km and large storm relative helix of 0-3km. As the storm move toward east with lower LCL (lifting condensation level), the bottom of the mesocyclone decreases gradually, and the tornado appeared finally. However, the 0-3km relative storm helix and 0-1.5 km vertical wind shear along Jianli storm moving direction are much weaker than that during the Funing tornado. The bottom level of the mesocyclone in the storm is not lower than 1.6 km, together with weaker intensity and more unstable duration of the mesocyclone. 3) The vertical structure characteristic of environmental humidity is an important factor to distinguish types of disastrously convective wind. During the storm activity in Jianli, Corresponding to observation records at automatic weather station, the pressure evolution is a cone-shape that quickly jumps up and drops rapidly with temperature decreasing. The pressure peak appeared 4 minutes earlier than the precipitation peak. It possibly indicates that the down speed of the airflow in the thunderstorm is significantly faster than that of raindrops, and is connected with strong evaporation of the water material when the deep environmental dry air in the mid-troposphere is involved in the convective storm. In Funing disaster, cool pool effect in surface is relative weak, corresponding with a very shallow dry layer in the middle layer and a deep saturated atmosphere in the low level of the environmental atmosphere.
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