雷达资料时间循环同化应用于闪电落区等研究初探

为研究夏季雷暴天气条件下的对流、降水、闪电的发展过程,有效使用高时空分辨率的遥感手段,如多普勒雷达、闪电定位仪等,利用中尺度数值模式ARPS及敏感的数据同化系统ADAS将VCP21模式下每6 min一次的雷达基数据资料进行时间循环同化,模拟得到相对可靠的三维空间、每10 min输出一次的对流云初步性态描述信息;进而结合目前公认的感应及非感应起电机制,通过云中电场强度与同化得到的云内相态模拟资料之间粗略微分关系,设定放电阈值,初步得到放电主要落点等信息;把本次模拟结果与江苏省闪电定位系统(LLS)实测资料做了对比,发现二者具有一定的可比性:(1)实测30 min内共有78次闪电,感应起电机制下共模拟出40次,非感应起电下有76次且首发时间较早。这也说明了非感应起电机制更易于雷暴云内电荷的衍生;(2)30 min内两种机制下模拟得到雷电发生的主要位置差别不大,和实测基本一致。

A PRELIMINARY STUDY ON APPLICATION OF RECURRENT ASSIMILATION OF RADAR OBSERVATIONS IN LIGHTNING FALL AREAS

To study summer thunderstorm processes,like convection,precipitation,lightning etc.,and efficiently use remote-sensing observations with high space-time resolution,such as Doppler radar,LLS(Lightning Location System) and the like,the meso-scale model ARPS and its Data Analysis System(ADAS) assimilated radar data,available every 6 minutes based on Nanjing Doppler weather radar observations of the VCP21 mode,are used to run time-recurrent assimilations,obtaining 3-d detail convective cloud informations with a time resolution of 10 minutes and a spatial resolution of 6km.Based on the widely recognized induction and non-induction electrification mechanisms,a coarse differentiation relationship is obtained from the differential relationship between electric intensity and intra-cloud physical quantities to set the discharge threshold at 250kv/m.And preliminary information on the main areas of lightning fall are obtained.Finally,the simulated results of starting time and lightning fall area are compared to the observations of Jiangsu LLS,which has the following indications.(1) There are 78 ground lightnings from the LLS in 30 minutes of observation,while there are 40 with the inductive mechanism and 76 with the non-inductive one,respectively,and lightnging start time of the latter is earlier than that of the former one.(2) It suggests that the non-inductive electrification mechanism is more likely to result in charge reproduction than the other one;and main lightning fall areas resulting from the two electrification mechanisms are in good agreement with each other and generally consistent with the in-situ LLS data as well.