Analysis on the Spatio-temporal Distribution Features of Lightning in Dalian Area from 2007 to 2008

Based on the cloud-to-ground lightning data from 2007 to 2008 obtained by the lightning detection and location system composed of 4 lightning detectors from different sites of Dalian area,the spatio-temporal distribution features of cloud-to-ground lightning in surrounding area of Dalian were analyzed from several aspects of lightning polarity distribution,daily variation,intensity and density.The results showed that the percentage of negative lightning to total number of lightning was 93.9%,with the average lightning intensity of 27.99 kA;the percentage of positive lightning was 6.1%,with the average intensity of 35.56 kA;daily variation of lightning frequency showed an obvious structure of two peaks and two valleys,two peaks value occured during 17:00-18:00 and 04:00-05:00,two valleys value occured during 09:00-10:00 and 00:00-01:00.The number of lightning appearing from May to Sep.was 91.5% of the total,among which,the lightning occured most frequently in Jun.to Aug.;the intensity of positive and negative lightning was mainly concentrated in 15-35 kA,over 80% lightning intensity was not more than 40 kA.The number of lightning whose intensity being less than 100 kA accounted for 99.3% of the total;the lightning density distribution had obvious regional difference,one high density area of lightning was Liaodong Bay,another was Dalian Bay;the lightning frequency in mainland area was much lower,coastal area was lightning disaster prevention focus in surrounding area of Dalian.