不同天气类型短时强降水与地闪特征分析

Characteristics of short-time heavy rainfall and cloud-to-ground lightning flash in different weather types

选取2006—2013年山东8次典型短时强降水(降水强度>20mm·h^-1)个例,并根据降水的天气尺度影响系统分为4种类型,利用山东区域ADTD型闪电定位仪资料,统计各类短时强降水与地闪相关性;结合地闪频数、密度分析地闪与短时强降水的雨强、出现时间、空间分布等特征的相关性。结果表明:1)各类强降水与不同范围地闪的相关性不同,与固定范围内地闪的时间、空间分布特征不同;其中负地闪占绝大多数,正闪比例小,负闪占比越大降水越强;站点周边30km范围内地闪频数与降水相关性较好,低槽冷锋型强降水与地闪频数相关性最好,其次是低涡切变线型,黄淮气旋型短时强降水与地闪频数相关性差,热带气旋型强降水则与正闪相关性更好。2)地闪频数只对单次过程降水量变化有所指示,不能直接用来判别短时强降水,而地闪频数峰值对于短时强降水预报有一定指示意义;其中后倾型低槽冷锋、西北涡、西南涡型短时强降水地闪频数峰值对于预报短时强降水指示意义较强,冷切变和暖切变型指示意义较小,前倾型低槽冷锋、黄淮气旋、热带气旋型无明显指示意义。3)高地闪密度与短时强降水落区对应较好,但短时强降水并不一定会出现在高地闪密度中心区域;大部分短时强降水极值站高地闪密度中心对应;对于后倾型低槽冷锋、暖切变、西南涡型短时强降水,5次·(10km)^-2·h^-1可作为预报参考阈值。

Eight typical short-time heavy rainfall cases(hourly precipitation greater than 20 mm)in Shandong from 2006 to 2013 are selected and classified into 4 types according to synoptic scale systems,and based on data of ADTD lightning location system in Shandong,The correlations between different types of short-time heavy rainfall and cloud-to-ground flashes(hereinafter referred to as ground flash)are studied.The correlations between ground flashes and characteristics of short-time heavy rainfall such as intensity,occurrence time,and spatial distribution are analyzed combined with ground flash frequency and plensity.The results are as follows.1)The correlations are different between heavy rainfall in different weather types and ground flash within different ranges,and the same is true between heavy rainfall in different weather types and spatial and temporal characteristics of ground flash within fixed ranges.Major ground flashes are negative among these types of short-time heavy rainfall and positive ground flashes account for a small percentage.The bigger the percentage of negative flashes,the stronger the precipitation.The correlation between ground flash frequency and precipitation is relatively good within 30 km from the station.The correlation between ground flash frequency of TypeⅠ(upper trough/cold front)short-time heavy rainfall and ground flash frequency is the best,followed by that between TypeⅡ(low vortex/shear line)short-time heavy rainfall and ground flash frequency,and that between TypeⅢ(extratropical cyclone)short-time heavy rainfall-Huanghuai Cyclone and ground flash frequency is poor.TypeⅣ(tropical cyclone)short-time heavy rainfall is better correlated to positive ground flashes.2)Ground flash frequency is indicative of the precipitation variation of a single process and cannot be directly used to distinguish short-term heavy rainfall,while the peak values of ground flash frequency give certain indications in forecasting short-term heavy rainfall.The peak values of ground flash frequency of TypeⅠshort-time heavy rainfall-backward-tilting upper trough/cold front and TypeⅡshort-time heavy rainfall-northwestern vortex and southwestern vortex give stronger indications,those of TypeⅡshort-time heavy rainfall-cold shear and warm shear give weaker indications,and those of TypeⅠshort-time heavy rainfall-forward-tilting upper trough/cold front,TypeⅢshort-time heavy rainfall-Huanghuai Cyclone,and TypeⅣshort-time heavy rainfall give no obvious indications.3)High ground flash density is well correlated to short-time heavy rainfall area,while short-time heavy rainfall will not necessarily happen in the center of high ground flash density;most stations of extreme short-time heavy rainfall are correlated to the center of ground flash density;the ground flash density of 5 times·(10 km)-2·h-1 can act as a reference threshold for forecasting TypeⅠshort-time heavy rainfall-backward-tilting upper trough/cold front,TypeⅡshort-time heavy rainfall-warm shear,and TypeⅡshort-time heavy rainfall-southwestern vortex.