“杜苏芮”(2023)台风外雨带闪电活动特征及与强降水微物理结构的关系

Lightning activity in the outer rainbands of typhoon Doksuri (2023) and its relationship with heavy rainfall microphysical structure

  • 摘要: 基于三维闪电定位和双偏振组网雷达精细观测资料,结合FY-4A 卫星TBB数据、地面自动站、台风资料、风廓线雷达及ERA5再分析资料等,运用统计及诊断方法分析了2023年台风“杜苏芮”雨带的对流性降水特征和闪电活动特征,详细分析了闪电活动与外雨带中尺度对流系统MCS(Mesoscale Convective System)上不同组织结构的强降水微物理特征的关系。结果表明:“杜苏芮”登陆过程中,台风眼壁及内外雨带均产生高效率的对流降水,外雨带对流降水在强度、影响范围及持续时间上较眼壁及内雨带降水显著。闪电活动在台风眼壁及内雨带频次较低。外雨带闪电频次最高,主要密集分布在外雨带的MCS上,且以负极性地闪活动为主。外雨带MCS成熟期存在不同组织结构的强雷暴云,其闪电活动空间差异大,闽东北沿海地区闪电稀少,而闽中沿海地区闪电频次高。利用双偏振雷达多参量的垂直结构反演结果,发现强降水-闪电不活跃区的强回波主体对流质心低,由高浓度的液态大雨滴组成,地面强降水为强烈的暖雨过程。相比而言,强降水-闪电活跃区的强回波主体对流质心更高,0℃层以上高度的冰相粒子含量更高、尺寸更大,0℃层以下有活跃的高浓度大雨滴也有冰相粒子,导致闪电活动活跃。0℃层以下,强降水-闪电活跃区具有深厚强上升气流,而强降水-闪电不活跃区以液相粒子为主,强上升气流层较浅薄。研究结果为台风外雨带闪电活动特征及与强降水微物理结构的关系提供了参考依据。

     

    Abstract: Base on observations of three-dimensional lightning location network, dual polarization weather radars, ground automatic stations and wind profile radars as well as FY-4A satellite TBB data, typhoon data, and ERA5 reanalysis data, convective precipitation features and characteristics of lightning activities within the rainbands of typhoon Duksuri that occurred in 2023 are analyzed. The relationship between lightning activities and microphysical characteristics of thunderstorm clouds with different organizational structures in the Mesoscale Convective System (MCS) within the outer rainband are analyzed in detail by using statistical and diagnostic methods. The results show that during Duksuri's landfall, both typhoon eyewall and the inner and outer rainbands produced convective precipitation with high efficiency. The convective precipitation in the outer rainband was more significant in terms of intensity, impact range and duration compared to that in the eyewall and inner rainband. Lightning activities had a lower frequency in the eyewall and inner rainband and the highest frequency was found in the outer rainband. Lightnings were mainly distributed in the MCS in the outer rainband, with negative cloud-to-ground flash being the main type. During the mature stage of MCS in the outer rainband, there were thunderstorm clouds with different convective structures, which produced significant differences in lightning frequency. Lightning frequency was lower in the coastal areas of northeastern Fujian, while it was much higher in the coastal areas of central Fujian. Based on vertical structure inversion results of dual polarization weather radar and multiple parameters, it is found that the strong thunderstorm clouds in the heavy rainfall-inactive lightning area had a low convective center of the main echo, which was composed of high-concentration liquid raindrops. Therefore, the heavy rainfall was caused by a strong warm rain process. In contrast, the main convective center of the strong echo in the heavy rainfall- active lightning area was higher, and the content and size of ice-phase particles on the melting layer were also higher. Below 0℃ layer, there were active high raindrops and ice phase particles, which led to the occurrence of intense lightning activity. Below 0℃ layer, there was deep and strong updraft in the mixed phase zone in the heavy rainfall-active lightning area, while the heavy rainfall-inactive lightning area was dominated by liquid phase particles, and the strong updraft layer was shallow. The above results provide a reference basis for the characteristics of lightning activities in the rain bands outside typhoons and their relationship with the microphysical structure of heavy rainfall.

     

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