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气象:2022,48(6):677-690
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副热带高压控制下河北局地强降水触发与维持机制分析
杨晓亮,王秀明,杨敏,朱刚
(河北省气象台,石家庄 050021;河北省气象与生态环境重点实验室,石家庄 050021;中国气象局气象干部培训学院,北京 100081;河北省气象行政技术服务中心,石家庄 050021)
The Trigger and Maintenance Mechanism of Local Flash Heavy Rain Under the Control of Subtropical High in Hebei
YANG Xiaoliang,WANG Xiuming,YANG Min,ZHU Gang
(Hebei Meteorological Observatory, Shijiazhuang 050021;Hebei Laboratory for Meteorological and Eco-Environment, Shijiazhuang 050021;China Meteorological Administration Training Centre, Beijing 100081;Heibei Meteorological Administrative and Technical Service Center, Shijiazhuang 050021)
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投稿时间:2021-08-12    修订日期:2022-04-01
中文摘要: 2018年8月5日晚上,河北中部局地强降水引发山洪并造成2人死亡。利用常规观测资料、地面自动站资料、NCEP再分析资料、VDRAS资料、风云四号气象卫星和多普勒天气雷达资料等,分析了强降水发生的环流背景及触发与维持机制。结果表明:强降水发生在500 hPa偏强偏北的西太平洋副热带高压控制之下,受北上台风云雀影响,河北上空水汽含量异常充沛:地面露点温度高达28~29℃,大气可降水量偏离气候平均达4σ以上,同时对流有效位能CAPE很大,0~6 km 深层垂直风切变很弱,环境条件有利于产生强降水。河北中部三处强降水形成的物理过程各不相同:保定东南部强降水的触发和增强系统为阵风锋,阵风锋向南、向东推进形成中尺度辐合中心,雷暴单体经过辐合中心合并增强、后向传播形成准静止雨带;保定西部强降水由边界层增强的偏东气流在太行山前迎风坡抬升触发,降水形成的冷池与偏东风对峙使回波在山前维持;保定东北部强降水经历了南北向对流云带和东西向对流云带两个阶段,是夜间最强降水阶段。6日01时保定东侧低空(距地1 500 m)加强的东南气流与其西侧正南气流形成的南北向辐合线使得南北向回波发展,随着东南气流转为正南气流,其与北侧偏东气流形成的准东西向暖式切变线使得回波转为东西向,夜间增强的低空偏南气流主导了保定东北部强降水回波的加强和维持,是决定强降水落区的关键因子。
Abstract:A local flash heavy rain process occurred in central Hebei Province in the evening of August 5, 2018, causing a flash flood and death of two people. The trigger and maintenance mechanisms of the flash heavy rain are analyzed using conventional observation data, ground automatic station data, NCEP reanalysis data, VDRAS data, FY-4 meteorological satellite and Doppler weather radar data. The results show that the flash heavy rain occurred under the control of the Western Pacific subtropical high at 500 hPa which was stronger and more northward than usual. Affected by the inverted trough of Typhoon Jongdari landing northward, the water vapor content above Hebei was abnormally abundant. The surface dew point temperature was as high as 28~29℃, and the atmospheric precipitable water deviated from the mean value by more than 4σ. In addition, the atmosphere was unstable and the environmental wind was weak, so the environmental conditions were conducive to the heavy rain. The physical processes leading to the torrential rain in three places in central Hebei were different. In the southeast of Bao-ding, the heavy rain was caused by the gust front moving southward and eastward to form a mesoscale convergence center, where thunderstorm cells merged, enhanced and propagated backward forming a quasi-stationary rain belt. The flash heavy rain in the west of Baoding was triggered by the enhancing easterly airflow in the boundary layer lifted by the windward slope of Taihang Mountain, where the echo maintained as a result of the cold pool formed by precipitation confronting with the easterly wind. The flash heavy rain in the northeast of Baoding experienced two stages: the north-south convective cloud belt and the east-west convective cloud belt, which was the heaviest precipitation at night. At 01:00 BT 6 August, the north-south convergence line formed by the south airflow strengthened at a low altitude (1500 m above the ground) on the east side of Baoding and the south airflow on the west side caused the north-south radar echo to develop. As the southeast airflow turned into a southerly airflow, the quasi-east-west-oriented warm shear line formed with the northeast airflow caused the echo to turn to east-west direction. The enhanced low-level south airflow at night dominated the strengthening and maintenance of the heavy rainfall echo in the northeastern part of Baoding, which was the key factor in determining the location of the flash heavy rain.
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基金项目:国家重点研发计划(2018YFC1507606)、中国气象局创新发展专项(CXFZ2021J029)和河北省重点研发计划项目(21375404D)共同资助
引用文本:
杨晓亮,王秀明,杨敏,朱刚,2022.副热带高压控制下河北局地强降水触发与维持机制分析[J].气象,48(6):677-690.
YANG Xiaoliang,WANG Xiuming,YANG Min,ZHU Gang,2022.The Trigger and Maintenance Mechanism of Local Flash Heavy Rain Under the Control of Subtropical High in Hebei[J].Meteor Mon,48(6):677-690.