“12·14雷打雪”过程的闪电特征及成因
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冯桂力,男,博士,正高级工程师,主要从事强对流天气及闪电活动研究,fenggl@lzb.ac.cn。

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P446;P412.25

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山东省自然科学基金项目(ZR2023MD025);山东省气象局科研项目(2022sdqxz8)


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Lightning characteristics and causes of “12·14” thundersnow process
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    摘要:

    2023年12月14日在山西和河北南部、河南北部、山东西部出现一次大到暴雪过程,并伴随频繁的闪电活动。利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代大气再分析(ECMWF Reanalysis v5,ERA5)资料以及闪电、大气电场仪、双偏振多普勒天气雷达等观测资料对此次“雷打雪”天气过程进行详细分析,得到以下研究结果:(1)此次“雷打雪”是一次明显的高架对流天气过程,低层一直存在逆温层,850~600 hPa为显著的暖湿平流,925 hPa以下近地面东北风形成的“冷垫”楔入到条件性对称不稳定层结下方,抬升暖湿空气,触发对流天气,释放不稳定能量,产生较强的上升运动。(2)降雪过程的雷电活动比较活跃,闪电频数高达99次·(10 min)-1,云闪和地闪比例为1.7∶1,正地闪的占比为19.4%。此次“雷打雪”天气过程的闪电空间分布和走向与强降雪落区表现出良好的一致性,闪电密集区域对应强降雪区域,74%的暴雪站周围30 km范围内出现闪电,100%的大暴雪站周围30 km内发生了闪电。(3)高空正KDP区域与地面降水率的增大密切相关。总闪电与6 km等高层雷达回波的空间一致性很好,基本分布在大于20 dBZ的云区内,闪电落区的回波顶高几乎都在5 km以上。雷达发现在5~8 km的高度范围出现ZDRKDP的正值区,揭示云内存在明显的垂直上升运动和过冷却液态水,存在良好云内起电条件,结合地面电场观测资料和闪电资料,推测此次降雪云系的电荷结构为上正下负的电荷结构。

    Abstract:

    On 14 December 2023, a heavy snowstorm occurred in the areas including southern Shanxi, southern Hebei, northern Henan, and western Shandong, accompanied by frequent lightning flashes. The ECMWF (European Centre for Medium-Range Weather Forecasts) Reanalysis v5 (ERA5) and the data of lightning, atmospheric electric field, dual-polarization radars are used to analyze the thundersnow process in detail, and the following results are obtained. (1) The thundersnow event is an obvious snowstorm system with elevated convection. In the snow area, there has been a temperature inversion layer at the lower troposphere, and significant warm and wet advection exists between 850 and 600 hPa. The northeasterly below 925 hPa forms a “cold pad” wedging into the conditional symmetric instable layer, where the warm and wet air is lifted to trigger convection and release instable energy, consequently producing relatively strong updraft. (2) The lightning activities during the snowfall are relatively active with the peak flash frequency of 99 times·(10 min)-1. The ratio of intracloud flashes to cloud-to-ground lightning activities is 1.7∶1 and the positive cloud-to-ground lightning activities account for 19.4%. The spatial distribution and trend of total lightning flashes in the thundersnow event show a good consistency with the snowfall area, and the area with dense lightning activities corresponds exactly to the heavy snowfall area. Lightning flashes are reported within 30 km around 74% of the weather stations with heavy snow (snowfall amount p≥10 mm), while lightning flashes occur within 30 km around 100% of the stations with heavy blizzard (p≥20 mm). (3) The positive KDP area aloft is closely related to the increase of surface precipitation rate. The spatial consistency between total lightning activities and radar reflectivity at high altitudes such as 6 km is very well because the total lightning activities are basically distributed in the cloud area with reflectivity larger than 20 dBZ, and the echo top height of the lightning falling area is almost above 5 km. It is found that the electrification conditions are good in the cloud where the presence of obviously strong updraft and supercooled liquid water is revealed by positive ZDR and KDP in the aloft layer of 5-8 km. Combined with the observations of surface electric field and lightning information, it is speculated that the charge structure of the cloud system during the snowfall may be a normal dipole pattern with positive above negative charge region.

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冯桂力,邢如峰,夏凡,朱文刚,于怀征.“12·14雷打雪”过程的闪电特征及成因[J].海洋气象学报,2024,(2):42-54.

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  • 收稿日期:2024-03-30
  • 最后修改日期:2024-04-26
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  • 在线发布日期: 2024-06-07
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