| There are more and more damage caused by lightning in recent decades, the safety of people’s lives and property is threaten by lightning. How to monitor and forcast lightning activity effectively is become a pressing issue today. China is vast in territory, the lightning location system cannot cover every region completely. At this time the world-wide lightning location network (WWLLN) shows its unique advantages which can cover large range. The correction for WWLLN is focused in this article. A performance assessment of the world-wide lightning location network (WWLLN) is presented using the lightning location system from Jiangsu province as ground truth. The characteristics of global lightning activities are analyzed by using WWLLN data from2008to2011. Further more, we research lightning activity characteristics, and its relationship between lightning frequency to the maximum winds in typhoon system. In this paper, the main results are as follows:(1) We estimate the propagation of the lightning-radiated electromagnetic field along the real irregular terrain around Yangzhou site and Nanjing site of Jiangsu province. The results show that the rough irregular terrain results in the rapid magnitude attenuation and the increase of the rise-time of the field waveform. To the Yangzhou site as the circumference of radius of45km, the root-mean-squared height (RMSH) of the real irregular terrain varies from7m to33m, the corresponding field attenuation percent ranges from1to11% and the extra rise-time increment relative to the ideal ground surface varies from0.1to0.6us, that resulting location error less than two hundred meters.(2) The lightning location system data in Jiangsu province is used as ground truth. Assess the performance of WWLLN system through establish a unique time and spatial windows criterion. The capabilities of WWLLN system detection efficiency and location accuracy are discussed in this section. The results indicate that during study period, the detect efficiency of CG flash is11.12%, and1.162%for IC, the total flash detection efficiency get3.152%. The detection efficiency for positive and negative flash is20.06%and13.93%respectively. The mean absolute location accuracy is11.66km with a standard deviation of10.45km. The location accuracy is found to have southward and eastward bias, with average location errors of0.662km in the east-west and0.412km in the north-south directions respectively.(3) The global lightning distribution for WWLLN system is in agreement to OTD/LIS system through the comparison of observation results. Global lightning activities mainly concentrated in low-latitude regions, the number of lightning can be accounted81.91%of total global flash in latitude30°N-30°N region. There are three lightning concentration areas, corresponding to America, Africa, and Eurasian continent; And The Pacific Ocean, The Atlantic ocean and The Indian Ocean, with a small number of lightning activity. It is fully demonstrated that mainland is the biggest component of world lightning activity.(4) Based on the lightning data from WWLLN and the typhoon data, we present the lightning activity characteristics and the relationship between the lightning frequency numbers and the maximum winds of55typhoons happened in the west pacific. The results show: in west Pacific, there are three distinct lightning flash regions in mature typhoon, one significant maximum in the eyewall regions about20-40km far from center, the other two are located in outer rainbands (280-340km and440-580km from center). Most of typhoons have lightning activity peaking before the maximum winds. The lag times ranges from0to24hours and the average lag times is26.6h. Therefore, the frequency of lightning activity has some implications for the typhoon intensity development within24h. |
PDF Full Text Request