Evolution of radar reflectivity and total lightning characteristics of the 21 April 2006 mesoscale convective system over Texas
Evolution of radar reflectivity and total lightning characteristics of the 21 April 2006 mesoscale convective system over Texas
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DOI：
10.1016/j.atmosres.2008.01.007
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发表时间：
2008-07
影响因子：
5.5
通讯作者：
C. L. Hodapp;L. Carey;R. Orville
中科院分区：
文献类型：
--
作者：
C. L. Hodapp;L. Carey;R. Orville
2006年4月21日，一个中尺度对流系统（MCS）在休斯顿（KHGX）运行天气监视雷达-1988多普勒（WSR-88 D，S波段）和休斯顿闪电探测和测距（LDAR）网络的范围内通过，该网络测量总闪电或云内闪电（IC）和云对地闪电（CG）的时间和三维位置。本研究记录了2006年4月21日德克萨斯州MCS的总闪电和雷达反射率的演变，重点是层状区域和对流区域中可能影响层状区域发展的过程。当MCS穿过LDAR网络时，系统慢慢成熟，对流线减弱，层状区域和雷达亮带发展。层状降水的面积增加了一个数量级，在雷达亮带及其上方的混合相区（0° ~ −10 °C），平均层状雷达反射率增加了7-8 dB。随着层状区域的成熟，总的闪电路径从对流线的后部向后和向下倾斜，进入层状区域。在早期，通道水平向后延伸40至50公里，进入10至12公里高度的层状区域。分析时间段结束时，总的闪电路径向后倾斜40公里，向下6公里，通过过渡区，然后在5至7公里的高度的层状区域延伸40至50公里。倾斜的路径可能是由于带电的冰粒平流从对流线的风暴相对前到后流，而水平路径进一步延伸到层状区域可能是由电荷平流和当地原位充电。随着层状云的发育，层状云总闪电率增加，总闪电高度减小。起源于层状区域的层状闪电占总闪电的百分比从10%显著增加到45%。层状云区的正地闪数也有所增加，其中73%起源于对流或过渡区。这两个原位充电机制的中尺度上升气流的发展和电荷平流的前到后流可能有助于增加带电和总闪电生产的层状区域。
On 21 April 2006 a mesoscale convective system (MCS) passed within range of the Houston (KHGX) operational Weather Surveillance Radar — 1988 Doppler (WSR-88D, S-band) and the Houston Lightning Detection and Ranging (LDAR) network, which measures the time and three-dimensional location of total, or both intracloud (IC) and cloud-to-ground (CG), lightning. This study documents the evolution of total lightning and radar reflectivity for the 21 April 2006 MCS over Texas, with emphasis on the stratiform region and those processes in the convection region that likely influence stratiform region development. As the MCS traverses the LDAR network, the system slowly matures with a weakening convective line and a developing stratiform region and radar bright band. The area of stratiform precipitation increases by an order of magnitude and mean stratiform radar reflectivity increases by 7–8 dB in the radar bright band and mixed-phase zone (0° to −10 °C) just above it. As the stratiform region matures, the total lightning pathway slopes rearward and downward from the back of the convective line and into the stratiform region. At early times, the pathway extends horizontally rearward 40 to 50 km into the stratiform region at an altitude of 10 to 12 km. Near the end of the analysis time period, the total lightning pathway slopes rearward 40 km and downward 6 km through the transition zone before extending 40 to 50 km in the stratiform region at an altitude of 5 to 7 km. The sloping pathway likely results from charged ice particles advected from the convective line by storm relative front to rear flow while the level pathway extending further into the stratiform region is likely caused by both charge advection and local in-situ charging. As the stratiform region matures, the stratiform region total lightning flash rate increases and total lightning heights decrease. The percentage of stratiform total lightning flashes originating in the stratiform region increases significantly from 10% to 45%. The number of positive CG flashes in the stratiform region also increases with 73% originating in the convective or transition regions. Both in-situ charging mechanisms created by the development of the mesoscale updraft and charge advection by the front to rear flow likely contribute to the increased electrification and total lightning production of the stratiform region.