摘要
利用常规气象观测资料、风廓线资料、北京观象台多普勒天气雷达产品、多普勒雷达变分同化分析系统(VDRAS)的反演资料和地面自动气象站客观分析资料,对2016年7月27日北京地区出现的一次雷暴大风天气的环境条件特征、风暴结构特征及演变机制进行了分析。结果显示:本次雷暴大风天气过程出现在弱天气尺度强迫环境中,较好的热力不稳定增强机制促使线状对流发展为弓形回波,形成雷暴大风天气。探空曲线中低层接近于干绝热的环境温度直减率和下沉对流有效位能突增等现象,对预报大风天气有较好的指示意义。上游雷暴的冷池出流与山前偏南暖湿气流在北京西部形成了明显的风向辐合,在强烈的扰动温度梯度和地形抬升的共同作用下,位于地面辐合抬升最强处触发新生单体并迅速发展。新生单体与风暴主体合并下山过程中,由于地形作用抬升了冷池出流高度,与平原地区偏南暖湿气流形成显著的不稳定层结,产生显著的扰动温度梯度,触发不稳定能量使雷暴在下山过程中强度增强。多普勒雷达产品上也表现为强的反射率因子核,并出现回波悬垂和有界弱回波区等特征,速度产品上可看到一对明显的端点涡旋。在冷池不断加强和端点涡旋对后入气流不断加速的共同作用下,后侧入流气流加强成为后侧入流急流,在低仰角速度产品上表现为显著的大风区。后侧入流气流将环境中的干冷空气夹卷进入云体,通过蒸发作用产生负浮力,使冷空气加速下沉,加之降水粒子的拖曳作用,最终造成剧烈的地面大风。
To investigate the environmental characteristics, storm structures and formation mechanism of the thunderstorm that occurred on 27 July 2016 in Beijing Area, the data of conventional observation, wind profile, Doppler weather radar, Variational Doppler Radar Analysis System (VDRAS) and automatic weather station (AWS) data are analyzed. The case analysis shows that this windstorm developed under a weak synoptic forcing background. The unstable thermodynamic condition enhanced the development of linear convection into bow echo, resulting in thunderstorm. The characteristic in sounding data such as the temperature laps rate in the lower troposphere was almost equal to the dry adiabatanda sudden increase of DCAPE, which are indicative of windstorm weather. The cold pool outflow and warm moist southerly flow at front of the mountain formed a convergence zone in the western region of Beijing. Under the combined action of significant disturbance temperature gradient and topographic forcing new thunderstorms were triggered. Because of the uplift of mountain area, the lifting of thunderstorm cold pool outflow caused significant disturbance temperature gradient, contributing to the development of the thermal instability, and triggered unstable energy, enhancing thunderstorm intensity in the process of coming down the hill. The Doppler radar product also showed a strong reflectivity core, an overhanging echo, boundary weak echo range and a book end vortex in radial velocity images. Under the combined action of the intensive cold pool and the book end vortex, the rear inflow was intensified, becoming rear inflow jet, which was characterized by a strong wind zone in the low elevation radial velocity images. The dry and cold air were trapped into the cloud by the rear inflow, creating a negative buoyancy through evaporation. Combined with the dragging of precipitation particles, eventually, strong surface winds were formed.
作者
程月星
孙继松
戴高菊
张慧洁
CHENG Yuexing;SUN Jisong;DAI Gaoju;ZHANG Huijie(Chaoyang Meteorological Office of Beijing, Beijing 100016;State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081)
出处
《气象》
CSCD
北大核心
2018年第12期1529-1541,共13页
Meteorological Monthly
基金
公益性行业(气象)科研专项(GYIIY201506009和GYIIY201506006)
中国气象局强对流预报专家创新团队
北京市气象局强对流天气机理研究创新团队共同资助
关键词
雷暴大风
雷暴增强
冷池
地形抬升
VDRAS
thunderstorm gale
storm intensification
cold pool
topographical lifting
Variational Doppler Radar Analysis System (VDRAS)
