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气象:2022,48(3):345-356
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秦巴山脉“4·23”区域性暴雨的若干异常特征
王晓芳,李山山,汪小康,李超,杨浩,崔春光,祁海霞
(中国气象局武汉暴雨研究所暴雨监测预警湖北省重点实验室,武汉 430205)
Anomalous Characteristics of Regional Torrential Rain in Qinling and Daba Mountains on 23 April 2021
WANG Xiaofang,LI Shanshan,WANG Xiaokang,LI Chao,YANG Hao,CUI Chunguang,QI Haixia
(Hubei Key Laboratory of Heavy Rain Monitoring Warning Research, Institue of Heavy Rain, CMA, Wuhan 430205)
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投稿时间:2021-06-20    修订日期:2021-09-30
中文摘要: 利用逐小时降水、雷达、FY-4A卫星等观测资料及ERA5逐时再分析资料,分析了2021年4月23日秦巴山脉大范围区域性暴雨过程的中尺度特征、水汽和环流异常特征,结果表明,该次暴雨过程范围大,多站降水量突破历史同期极值,且大巴山区出现了山地突发性暴雨事件。500 hPa秦巴山脉异常的“东高西低”环流形势维持使得青藏高原至陕西间的气压梯度力增大,中层西风气流增强。中低层多尺度天气系统的叠加作用是造成该次暴雨的背景动力条件,西南低涡前方的东南气流一方面与北侧偏东风形成的切变线为暴雨发生提供了环境场的辐合上升运动,另一方面将西南气流和偏南气流带来的水汽输送到秦巴山脉汇聚。同期近海台风和东北冷涡活动相关联的环流导致东北路径的水汽输送异常强(贡献达到30%),成为本次暴雨过程水汽来源的独特之处。与历史同期比,偏南通道和东北通道的水汽路径上比湿都是异常的正距平,说明暴雨期水汽来源丰沛。暴雨过程主要由西南低涡前方的一个中尺度对流系统活动造成,大巴山区迎风坡对气流的地形抬升与环境场偏南气流的辐合上升叠加,对流活动强,降水强度大且突发性强;而秦岭山区近地面是偏东风在山前辐合抬升,中层为西南引导气流的环境场上升运动,比大巴山区降水期的上升运动弱,主要以层云降水为主,但持续时间长,累计降水量大。异常环流条件下多尺度系统相互作用、异常水汽输送结合地形影响是秦巴山脉暴雨发生的主要原因。
Abstract:Using hourly precipitation, radar, FY-4A satellite and other observational data, and ERA5 hourly reanalysis data, this paper analyzes the mesoscale characteristics, moisture and circulation anomalies of the large-scale regional torrential rain process in the Qinling and Daba Mountains on 23 April 2021. The results showed that the heavy rain occurred in a large area, and the precipitation at many stations broke through the historical extreme values. Meanwhile abrupt extreme torrential rain attacked the Daba Mountains. At 500 hPa, the abnormal “high in the east and low in the west” circulation situation over the Qinling and Daba Mountainous area increased the pressure gradient between Shaanxi and the western Qinghai-Tibet Plateau, causing the mid-level westerly airflow to have increased. At the same time, the superimposition of the mid- and low-level multi-scale weather systems provided the background dynamic condition for the torrential rain. The southeast airflow in front of the southwest vortex and the easterly wind on the north side formed a shear line that caused the convergence ascending motion of the environmental field while the other side transported the water vapor brought by the southwesterly airflow and the southerly airflow to the Qinling and Daba Mountains to converge. The circulation associated with the long-distance typhoon and the northeast cold vortex activity in the same period caused the abnormal water vapor transportation (30%) of the northeast path to be the unique source of water vapor for this torrential rain process. Compared with the same period in history, the specific humidity on the water vapor path of the south passage and the northeast passage was abnormally positive, indicating that there was abundant water vapor during the torrential rain period. The torrential rain process was mainly caused by the activity of a mesoscale convective system (MCS) in front of the southwest vortex. The topographical uplift of the windward slope of the Daba Mountains and the convergent ascending of the southerly airflow in the environmental field were superimposed. Sufficient water vapor at the lower level was transported vertically to the upper level by strong ascending motion, with strong convective activity, severe hourly rainfall and strong abruptness. However in the Qinling Mountains, the easterly wind converged and rose in front of the mountain, and the ascending movement of the environment field with southwestern airflow in the middle layer was weaker than that in the Daba Mountainous area during the severe precipitation period, and was dominated by stratiform precipitation. But the severe precipitation lasted for a long time, so the accumulated precipitation was a lot. In a word, multi-scale system interactions, abnormal water vapor transport combined with topographical influence under abnormal circulation conditions are the main reasons for the occurrence of this torrential rain process in the Qinling and Daba Mountains.
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基金项目:国家重点研发计划(2018YFC1507200)、国家自然科学基金项目(41975058、41620104009、91637211)和湖北省气象局科技发展基金项目(2019Z03,2021Q04)共同资助
引用文本:
王晓芳,李山山,汪小康,李超,杨浩,崔春光,祁海霞,2022.秦巴山脉“4·23”区域性暴雨的若干异常特征[J].气象,48(3):345-356.
WANG Xiaofang,LI Shanshan,WANG Xiaokang,LI Chao,YANG Hao,CUI Chunguang,QI Haixia,2022.Anomalous Characteristics of Regional Torrential Rain in Qinling and Daba Mountains on 23 April 2021[J].Meteor Mon,48(3):345-356.