春季与夏季两次雷暴大气结构及地闪特征对比  

Influence factors comparing of thunderstorm between spring and summer in Nanjing

作　　者：孙哲[1] 魏鸣[1] 

机构地区：[1]南京信息工程大学中国气象局气溶胶与云降水重点开放实验室,江苏南京210044

出　　处：《大气科学学报》2016年第2期260-269,共10页Transactions of Atmospheric Sciences

基　　金：国家重点基础研究发展计划(973计划)项目(2013CB430102);地理信息科学教育部重点实验室开放研究基金资助项目(KLGIS2015A01);公益性行业(气象)科研专项(GYHY201306040);航空科学基金资助项目(201320R2001)

摘　　要：利用NCEP再分析资料、探空资料、闪电定位资料和南京、常州多普勒雷达资料,通过对比分析南京2012年2月22日春季雷暴和2011年8月10日夏季雷暴两次过程,研究不同季节影响雷暴发生的大气结构以及强弱雷暴地闪特征的差异。结果表明:风矢位温(V-3θ)图揭示的大气动力热力水汽特征能够为雷暴的潜势预报提供先兆信息。两者相较而言,春季雷暴的动力抬升作用明显;夏季雷暴主要由热对流引起,对流层上层的动力抽吸作用不明显。春季弱雷暴正地闪在总地闪中所占比例较高。无论春季弱雷暴还是夏季强雷暴,地闪落点与辐合区对应关系明显,且地闪的落点也与雷达反射率因子有较好的对应关系:地闪主要分布在强回波区(大于40 d Bz)及其外围区域。但在较强雷暴云的发展阶段,地闪多发生在风暴体伸展方向的一侧,具有引导雷达回波移动的作用,夏季强雷暴地闪簇集在垂直风切变区域。A comparative analysis of two thunderstorms that occurred in the Nanjing area was conducted by using NCEP,sounding,lightning location and Doppler radar data,in Nanjing and Changzhou,with the aim being to study the differences among the key factors causing thunderstorms in spring and summer. One of the thunderstorms took place on 22 February 2012,and the other was on 10 August 2011.The results of the analysis of the atmospheric energy structure showthat the wind-potential temperature plots can reveal the dynamic,thermodynamic and water vapor characteristics before the occurrence of thunderstorms.Specifically,the tropopause height increases,providing sufficient space for the development of the thunderstorm.The ＂ultra-low＂temperature phenomenon of the tropopause is a sign of thermal instability,while the clockwise rotation of the wind direction along with an increase in the height provides favorable dynamic conditions for the thunderstorm. Meanwhile,large quantities of water vapor are transported by the moisture gradient in the vertical direction.Comparison of the physical diagnosis reveals that the dynamical lifting effect of the spring thunderstorm is stronger than that in summer,with the latter mainly caused by heat convection; the dynamical suction effect in the upper troposphere is not predominant. Comparison of the characteristics of Cloud-to-Ground（ CG） lightning evolution indicates that the CG lightning frequency of the spring thunderstorm is low,but the percentage of positive CG lightning is high. The situation for the summer storm is just the opposite,showing multiple peaks. The percentage of negative CG lightning is high. In the mature stage,the radar echo top height has a negative correlation with the CG flash rate,and it reaches its peak before the occurrence of CG flashes. Comparison of the radar data shows that the echo of the spring thunderstorm appears similar to a stratocumulus cloud precipitation echo. There is obvious wind shear,strong warm advection,and convergence activities in the stor

关 键 词：地闪 雷达回波 雷暴 动力 热力 

分 类 号：P446[天文地球—大气科学及气象学] P427.3