雅安地区一次暖区暴雨过程的对流触发机制分析  

Analysis of the Convective Triggering Mechanism of A Warm-Sector Rainstorm in the Ya’an Region

作　　者：竹利 蒋兴文[1,2] 卢萍[1,2] 师锐 ZHU Li;JIANG Xingwen;LU Ping;SHI Rui(Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province,Institute of Tibetan Plateau Meteorology,China Meteorological Administration,Chengdu 6100722 Institute of Tibetan Plateau Meteorology,Chinese Academy of Meteorological Sciences,Beijing 100081)

机构地区：[1]中国气象局成都高原气象研究所/高原与盆地暴雨旱涝灾害四川省重点实验室,成都610072 [2]中国气象科学研究院/青藏高原气象研究院,北京100081

出　　处：《大气科学》2024年第5期1693-1710,共18页Chinese Journal of Atmospheric Sciences

基　　金：四川省科技计划重点研究项目2022YFS0540;四川省自然科学基金项目2022NSFSC0021;国家重点研发计划项2022YFC3003902;灾害天气国家重点实验室开放课题项目2021LASW-A06;中国气象局西南区域气象中心创新团队基金XNQYCXTD-202202;高原与盆地暴雨旱涝灾害四川省重点实验室项目SCQXKJYJXMS202208。

摘　　要：本文利用多源高分辨率资料,对2021年8月4日四川雅安地区大暴雨过程中对流发展最为旺盛的第二阶段的对流触发机制进行了分析,结论如下:(1)对流层中层的中尺度低压系统为过程第二阶段的对流触发和发展提供了有利的动力和热力条件。(2)冷池出流作用下形成的地面辐合线可直接触发对流,而下坡风及地形绕流作用下形成的地面辐合线难以直接触发对流,需边界层中上层存在“二次抬升机制”配合才容易触发对流,“二次抬升机制”包括环境大气辐合抬升、高海拔地形强迫抬升、移动的残余弱对流系统前侧上升气流耦合抬升机制。(3)在地形机械强迫作用下峨眉山东北侧形成的正涡度区有利于对流加强发展,强对流系统激发的低空急流北移与龙门山南下的冷池出流相遇后触发“高架对流”,该对流触发机制与峨眉山及附近的高海拔山地有密切关系,可能为青藏高原东坡地带特有的一种对流触发机制。(4)不同触发机制作用下,升力形成与对流启动的时差和距离有所不同,其中下坡风及地形绕流作用下的时差更长,距离更远。In this paper,multisource high-resolution data are used to analyze the triggering mechanism of convection at the second stage of the most vigorous development of convection during the heavy rain in Ya’an,Sichuan,on August 4,2021.The conclusions from this study are as follows.(1)The mesoscale disturbance system in the middle and upper troposphere provides favorable dynamic and thermodynamic conditions for the trigger and development of convection in the second stage of this heavy rain(2)The surface convergence line formed by the cold pool outflow can directly trigger convection,whereas that formed by mountain-to-plain flows and topographic circumfluence cannot directly trigger convection.Convection can be easily triggered only when there is a“secondary uplift mechanism”in the upper and middle layers of the boundary layer.This“secondary uplift mechanism”includes the coupling uplift mechanism of the ambient atmospheric convergence and uplift,forced uplift of high-altitude terrain,and upstream updraft in front of the moving residual weak convection system.(3)The positive vorticity zone formed on the northeast side of Mount Emei under the mechanical forcing of terrains is conducive to the strengthening and development of convection.Furthermore,the low-level jet generated by the strong convective system moves northward and meets the cold pool outflow south of Mount Longmen,triggering the“elevated convection.”This convection triggering mechanism is closely related to Mount Emei and nearby high-altitude mountains and may be a unique convection triggering mechanism in the eastern slope of the Qinghai–Tibet Plateau.(4)Under the action of different triggering mechanisms,the time difference and relative position of lift formation and convection initiation vary.Compared with the cold pool outflow and terrain uplift,the time difference is longer and the distance is farther under the influence of downhill wind and terrain flow.

关 键 词：对流触发机制 地面辐合线 对流初生 冷池 

分 类 号：P458[天文地球—大气科学及气象学]