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绍兴南部山地雷暴大风特征与地形作用研究

Study on the characteristics and terrain effect of thunderstorm gale in the southern mountainous area of Shaoxing

  • 摘要: 基于2017—2021年绍兴及周边地区714个国家、区域气象观测站和雷电观测、ERA5再分析以及台风路径等资料,分析了绍兴及周边地区雷暴大风的时空分布特征以及南部山地不同天气型雷暴大风的环流特征,并利用ERA5资料计算的对流参数研究了三次雷暴大风天气过程中山地地形的作用。结果表明: (1) 绍兴及周边地区雷暴大风年平均次数空间分布不均,两个明显高发区位于南部山地会稽山脉西侧和四明山脉西南侧。(2) 绍兴南部山地雷暴大风主要出现在3—9月的下午至前半夜,日变化峰值较为显著,后半夜至上午也常发生;平原地区后半夜至上午很少发生雷暴大风。(3) 绍兴南部山地雷暴大风的天气型有三类:高空冷平流强迫型、低层暖平流强迫型和准正压型,其中准正压型最多(66.3%),此型中副热带高压作用显著。(4) 绍兴南部山地地形对雷暴大风作用分为两类:一是动力作用,山地导致迎风坡气流抬升,加强上升运动;二是热力作用,山地的存在使得自由对流高度和下垫面的高度差随海拔高度的增加而减小,对流更容易产生,其作用主要发生在午后时段。

     

    Abstract:
    Based on data from 714 national and regional weather observation stations, lightning observations, ERA5 reanalysis, and typhoon tracks from 2017 to 2021, this study analyzed 1) the spatiotemporal distributions of thunderstorm gale in Shaoxing and surrounding areas, 2) circulation characteristics of the different weather types of thunderstorm gale in the southern mountainous regions, and 3) investigated the role of terrain in three thunderstorm gale events using convection parameters by the EAR5 data. The results are as follows. (1) The spatial distribution of the annual average frequency of thunderstorm gale shows two obvious high incidence areas near the southern mountainous terrain in Shaoxing, namely the westside of the Kuaiji Mountains and the southwest side of the Siming Mountains. (2) Thunderstorms gale in the southern mountainous areas of Shaoxing mainly occur from the afternoon to the early half of the night with significant daily peak variation from March to September. It also often appears in morning and the late half of the night, rarely occurs in the plain areas in morning and the late half of the night. (3) There are three typical weather types for thunderstorms gale in the southern mountainous areas of Shaoxing with different forcing: a) cold advection, b) warm advection, and c) quasi-barotropic. Among them, the quasi-barotropic category is the most common (66.3%), in which the subtropical high pressure plays a significant role. (4) There are two formation mechanisms of thunderstorm gale in the southern mountains: First, mountain terrain leads to the airflow uplift and strengthen the upward movement; Second, the existence of mountain reduces the height difference between the free convection height and the underlying surface with increasing altitude, making convection more likely to occur. However, thermal effects mainly occur in the afternoon
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