Thunderstorms are a type of convective weather phenomenon that happen frequently in nature with high intensity.The United Nations Committee for Disaster Reduction has referred to lightning as "one of the ten worst natural disasters".Jiangsu Province is in the transition zone between the subtropical and warm temperate zones,and is one of the provinces in China most frequently affected by lightning.As a relatively wealthy province in economic terms,the electrical infrastructure(power grid,electrical equipment etc.) of Jiangsu is also well-developed.Therefore,when lightning-related accidents occur,incalculable harm can be caused not only to personal safety but also socioeconomically.To develop a deeper understanding of the laws governing lightning activities in Jiangsu Province,as well as improve lightning protection and disaster reduction services,the present study set about analyzing the lightning characteristics of the region(interannual variation,monthly variation and daily variation),based on data from two sources:the Advanced Time of Arrival and Direction System(ADTD) and the Worldwide Lightning Location Network(WWLLN).The ADTD data were provided by Jiangsu Meteorological Department,whose time zone is Beijing standard time(BST).Because the time zone of the WWLLN is Greenwich Mean Time(GMT),we converted GMT to Beijing time.The study spanned a period of four years,from 2006 to 2009,throughout contiguous Jiangsu Province.When carrying out the study,the detection efficiency of ADTD was assumed to be 100% because the ADTD data were considered to be the "ground truth",and a time-matching window of 0.5 ms was chosen for the lightning location data of WWLLN/ADTD(i.e.,when lightning observed by WWLLN occurred 0.5 ms before or after that of ADTD,the flash was considered to have been captured by WWLLN).The WWLLN and ADTD data were then processed and analyzed for the study period.The analysis confirmed that WWLLN favors high peak current return stroke lightning discharges.Meanwhile,WWLLN could not distinguish the lightning polarity.For example,it was unable to distinguish a positive flash from a negative flash.The polarity could,however,be determined by simultaneous observation with ADTD.WWLLN showed good correspondence with ADTD in terms of the temporal and spatial distribution of lightning activities.Specifically:the frequency difference between day and night was not large;the number of lightning flashes occurring during the day was slightly higher than at night;and the lightning mostly occurred in the period from June to August,especially midsummer,which was clearly the most active season.The amount of lightning detected by WWLLN from June to August was about 83.09% of the total amount in one year,while the amount of lightning detected by ADTD was 88.48%.During a day,the highest peak of lightning appeared at roughly 04:00 PM Lightning mainly occurred in the period between 13:00 BST and 20:00 BST,while low-level activity occurred between 02:00 BST and 11:00 BST on the second day.The lightning flash density in Jiangsu Province was higher in western regions than in eastern regions,and also higher in southern regions than in northern regions.Besides,those regions with frequent occurrence of lightning activity roughly coincided with the most economically developed parts of Jiangsu Province.The cloud-to-ground detection efficiency of WWLLN was shown to improve greatly from the first to the fourth year of the study,with an overall detection efficiency of cloud-to-ground flashes increasing from 3.95% in 2006 to 11.58% in 2009,possibly due to the increased number of stations and upgrading of the algorithm.The detection accuracy of WWLLN is now approximately 100 km,but its ultimate goal is an accuracy of 10 km.On the whole,the lightning density determined by WWLLN was much lower than that of ADTD,Compared to ADTD,WWLLN failed to detect the high incidence of lightning in the central area of Jiangsu,The difference in the detection accuracy is related to the characteristics of WWLLN itself;WWLLN is a large-scale(worldwide) lightning location system whose detection accuracy is often hundreds or even thousands of kilometers,The detection efficiency was related to the polarity and strength of the return stroke,The detection efficiency of positive ground flashes was higher than that of negative ground flashes,Meanwhile,the greater the peak current of the return stroke was,the more accurate the detection efficiency of WWLLN would be.