| 摘要: |
| 利用广州S波段双偏振雷达观测数据和低频电场探测阵列三维闪电定位数据，分析了2017年5月4日和5月8日华南地区两次飑线过程中闪电起始和通道位置处的雷达偏振参量和降水粒子特征。两次飑线中约80%的闪电起始和通道（统称闪电放电）定位于对流区。对流区闪电放电位置处的雷达反射率（ZH）要比层云区平均大4~5 dBZ，其它偏振参量的平均值较为接近。闪电放电位置处的ZH中值随高度增加而减小，但差分反射率（ZDR）、差分传播相移率（KDP）和共极化相关系数（CC）在?10 ℃层以上随高度变化不大；?10 ℃层以下，对流区闪电放电位置对应ZDR和KDP随高度下降明显增大。闪电起始位置的平均ZH比闪电通道位置处的平均ZH大1~2 dBZ，但前者在对流区内对应ZH分布峰值区间为25~30 dBZ，弱于后者的30~35 dBZ；同时，它们的对比关系在?20 ℃层上下不同。对流区内闪电放电位置处的主导性粒子是霰和冰晶，它们的区域占比接近。在层云区内，闪电放电位置主要是干雪和冰晶，干雪区域的占比显著大于冰晶。 |
| 关键词: 飑线 三维闪电 闪电起始 闪电通道 双偏振雷达参量 降水粒子 |
| DOI：10.16032/j.issn.1004-4965.2021.035 |
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| CHARACTERISTICS OF CLOUD MICROPHYSICS AT POSITIONS WITH FLASH INITIATIONS AND CHANNELS IN CONVECTION AND STRATIFORM AREAS OF TWO SQUALL LINES |
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ZHAO Chuanhong1,2, ZHENG Dong3, ZHANG Yijun4, LIU Xiantong5, ZHANG Yang6, YAO Wen4, ZHANG Wenjua4
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1. Department of Atmospheric and Oceanic Sciences& Institute of Atmospheric Sciences, Fudan University, Shanghai 200438, China;2. State Key Laboratory of Severe Weather/ Laboratory of Lightning Physics and Protection Engineering, Chinese Academy of Meteorological Sciences, Beijing 100081, China;3.Suzhou Meteorology Bureau, Suzhou 215131, China;4.State Key Laboratory of Severe Weather/ Laboratory of Lightning Physics and Protection Engineering, Chinese Academy of Meteorological Sciences, Beijing 100081, China;5.Department of Atmospheric and Oceanic Sciences& Institute of Atmospheric Sciences, Fudan University, Shanghai 200438, China;6.Guangzhou Institute of Tropical and Marine Meteorology, China Meteorological Administration, Guangzhou 510641, China
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| Abstract: |
| Using data from polarimetric radars and three-dimensional lightning detection, we investigate the characteristics of polarimetric variables and hydrometeors at positions with flash initiations and channels in two squall lines that occurred over Southern China on 4 and 8 May 2017, respectively. It is found that the located lightning pulse discharge events associated with flash initiations and channels (they are collectively called lightning discharges (LDs)) in the convection areas both account for approximately 80% of their respective samples. The average horizontal reflectivity (ZH) at the radar grid boxes with LDs in the convection areas is about 4~5 dBZ larger than that in the stratiform area, while the average values of other polarimetric variables (differential reflectivity (ZDR), specific differential phase (KDP) and co-polar correlation coefficient (CC)) associated with the LDs are similar in the convection and stratiform areas. The median ZH at the positions with LDs decreases with increasing altitude. Meanwhile, median ZDR, KDP, and CC associated with the LDs keep relatively constant above the ?10 ℃ layer. Below the ?10 ℃ layer, median ZDR and KDP at positions with LDs distinctly increase with decreasing altitude. Moreover, the average ZH associated with flash initiations is approximately 1~2 dBZ bigger than that corresponding to the flash channels, whereas, in the convection areas, the peak interval of ZH associated with flash initiations is 25~30 dBZ, smaller than that corresponding to flash channels (30~35 dBZ). Furthermore, the peak interval of ZH corresponding to flash initiations and channels is different above and below the ?20 °C level. The dominant hydrometeors at positions with LDs are graupel and ice crystals in the convection areas, and their areas are analogous; meanwhile, the corresponding dominant hydrometeors are dry snow and ice crystals in the stratiform area, and the area of dry snow is distinctly bigger than that of ice crystals. |
| Key words: squall line three-dimensional lightning flash initiation flash channel polarimetric radar variables hydrometeors |
