Journal of Arid Meteorology ›› 2022, Vol. 40 ›› Issue (1): 62-72.DOI: 10.11755/j.issn.1006-7639(2022)-01-0062

• Articles • Previous Articles     Next Articles

Analysis of trigger mechanism of a mesoscale covective system in western mountainous area of Fujian

FENG Jinqin1,2(), LU Yunyun3, LAI Qiaozhen1, CAI Jing1   

  1. 1. Longyan Meteorological Bureau of Fujian Province, Longyan 364000, Fujian, China
    2. Fujian Key Laboratory of Severe Weather, Fuzhou 350001, China
    3. Xinluo Meteorological Bureau of Fujian Province, Xinluo 364000, Fujian, China
  • Received:2021-04-06 Revised:2021-08-06 Online:2022-02-28 Published:2022-02-28

福建西部山区一次中尺度对流系统触发机制分析

冯晋勤1,2(), 卢芸芸3, 赖巧珍1, 蔡菁1   

  1. 1.福建省龙岩市气象局,福建 龙岩 364000
    2.福建省灾害天气重点实验室,福建 福州 350001
    3.福建省新罗区气象局,福建 新罗 364000
  • 作者简介:冯晋勤(1977— ),女,正研级高级工程师,主要从事天气预报工作. E-mail: lyfjq@hotmail.com
  • 基金资助:
    福建省自然科学基金项目(2019J01099);福建省自然科学基金项目(2020J01099);福建省自然科学基金项目(2021J01450);福建省气象局开放式基金共同资助(2018K01)

Abstract:

Based on the conventional observation data, automatic weather station data, wind-profiling radar and CINRAD-SA Doppler radar data as well as ERA-Interim 0.125°×0.125° 6 h reanalysis data, the extreme severe rain occurring in the west area of Fujian on 19 May 2015 was analyzed. The results show that the extreme severe rain process included two stages: warm area precipitation and frontal precipitation. The heavy rain area located in the left of south-west jet. Sufficient water vapor, the confluence of cold and warm air, the strengthening of unsteady convective stratification, decrease of lifting condensation and free convection height and moderate vertical wind shear over the rainstorm-hit area were all favorable to the development of MCS. During the warm area precipitation, southwest airflow was converged on the southwest side of rainfall area. The air with sufficient water vapor and high energy was lifted by the cold outflow air near the mesoscale boundary. New convective cells generated continuously. The convective cells moved to the east-northeast and formed a short rain belt. Several NE-SW short oriented rainbands established on the north side of the outflow boundary, moving eastward slowly and affecting the rainfall area repeatedly. Convergence line and wind speed convergence over the rainstorm area provided a good dynamic lifting condition for precipitation. The convective cells were strengthened by the valley topography opening to the southwest. The continuous back-building of convective cells and several NE-SW oriented rainbands were two major developing modes of MCS. During the frontal precipitation, with the shear of low-level vortex moving eastward and southward, new convective cells were born in the region of wind speed convergence, water vapor and high energy and moved southeast. Northwest wind of middle and high level showed forward tilting feature. The vertical wind shear increased. The confluence of cold and warm air caused rainfall strengthening and maintenance. Backward prorogation and eastward moving of convective cells forming train effect was the main developing mode of MCS.

Key words: Fujian, extreme severe rain, mesoscale characteristics, mesoscale boundary, forward tilting feature, train effect

摘要:

利用常规天气资料及地面自动站、风廓线雷达、新一代天气雷达资料和ERA-Interim逐6 h 0.125°×0.125°再分析资料,分析2015年5月19日福建西部山区一次极端降水的中尺度特征。结果表明:(1)极端降水分为锋前暖区降水和锋面降水两个阶段,暴雨区位于低空西南急流轴左侧,水汽充足,冷暖空气交汇,不稳定能量大,抬升凝结高度和自由对流高度低,大气可降水量大及中等强度的垂直风切变形成有利于中尺度对流系统(mesoscale covective system, MCS)发展的环境条件。(2)锋前暖区降水期间,西南气流携带高能量和水汽充足的空气移入暴雨区被中尺度边界附近的冷出流空气抬升,不断产生新的对流单体,对流单体向东北偏东方向移动,排列形成短雨带;若干条东北—西南向长度不等的短雨带在中尺度出流边界北侧建立,缓慢向东移动,依次重复影响关键区;暴雨关键区存在辐合线和风速辐合,为降水提供了良好的动力抬升条件;向西南开口的河谷地形加强了对流的发展;对流单体不断后部建立和东北西南向多个短雨带重复影响同一地区的列车效应是此阶段MCS主要发展方式。(3)锋面降水期间,对流单体在低涡切变南侧风速辐合、水汽和能量大值区发展东移南压,中高层先于低层转偏北气流,表现出前倾特征,垂直风切变加大,冷空气从中高层先扩散南下,与低层暖湿空气交汇使对流加强,冷暖气流的交汇叠加风速辐合使得强降水加强并维持。对流单体后向传播向东移动产生的列车效应是此阶段MCS主要发展方式。

关键词: 福建, 极端降水, 中尺度特征, 中尺度出流边界, 前倾特征, 列车效应

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