Correlation Research On Lightning And Aerosols

In order to better understand the effects of aerosols on lightning,this article uses lightning data provided by LIS/OTD,aerosol optical thickness(AOD)provided by MODIS,ice cloud optical thickness(IOT),and ground temperature and relative humidity provided by reanalysis data of NCEP/NCAR,altitude data to study which factors in the two regions with different concentrations of aerosols in China played a leading role in lightning activity and how aerosol concentrations affected lightning activity in the two regions.On this basis,this article also uses the lightning location data and atmospheric aerosol composition(SO2,PM10,PM2.5)data and so on to analysis in depth of the average annual lightning density,ground flash,and positive ground flash ratio in the summer of Nanjing region and the atmospheric aerosol composition.In the selected study area,the main influencing factors of lightning activity in different regions are different.The result of region with relatively lower aerosol concentration(AODave=0.14)shows that surface temperature(Rp=0.745,Rp:partial correlation coefficient)and altitude(Rp=-0.613)may be the two main factors affecting lightning activity.The result of region with relatively higher aerosol concentration(AODave=0.60)suggests that surface temperature(RP=0.870),aerosol concentration(Rp=-0.823)and relative humidity(Rp=0.818)may be the main factors affecting lightning activity.In addition,the effect of low and high aerosol concentration on lightning activity is opposite.The region with low aerosol concentration,lightning density and AOD,IOT is significant positive correlation(R=0.81,0.82),aerosols may increase the number of cloud droplets mainly through microphysical processes,with the consequent increase of ice particle content,enhancement of thunderstorm cloud activity and promotion of lightning activity.The region with high aerosol concentration,lightning density and AOD is significant negative correlation(R=,0.78),surface temperature and AOD is negative correlation(R=-0.29),however,IOT and lightning density is no correlation,show that aerosols can affect lightning activity by relative effects,aerosols absorb sunlight,reduce the solar radiation to reach the Earth’s surface,surface temperature is decreased,and then the intensity of the thunderstorm cloud decreased,so that the content of ice particles decreased,eventually resulting in reduced lightning activity.We believe that the critical value AOD of the aerosol microphysical effect and radiation effect is about 0.3.The aerosol concentration of Nanjing is higher,where AODave is 0.905,which is far beyond the critical point of microphysical and radiation effects of aerosols.Based on observations from 2002 to 2011,it was found that the average annual lightning density was negatively correlated with AOD in the summer(R=-0.634).We believe that the aerosol impact on lightning activity in Nanjing is dominated by aerosol radiation effects.On this basis,the analysis of the correlation between atmospheric aerosol composition and cloud-ground flash in Nanjing reveals that PM10 has a good negative correlation with total lightning(R=-0.52).There was a weaker negative correlation between SO2,PM2.5 and total flash(R=-0.13,R=-0.45).In the surface atmospheric aerosol composition selected in Nanjing,particulates through radiation effects,is the main aerosol molecules that affect cloud-ground flash.Through a more in-depth analysis of the correlation between positive ground flash ratio and atmospheric aerosol composition,we found that SO2,PM10 and PM2.5 have a strong negative correlation with positive lightning ratio(R=-0.51,-0.81,-0.85).It shows that the microphysical effects of aerosols still play a role in the charge structure of thunderstorm clouds.The dense of SO2、PM10、PM2.5 increases,which results in increase of thunder cloud graupel particles formed under the inductive electrification mechanism of negative charge.It’s more likely to produce negative ground flash,the number of negative ground flashes in Nanjing has gradually increased while the number of positive ground flashes has gradually decreased.