Estimation Of Lightning-Generated NOX In China Based On Cloud-to-Ground Lightning Location Data And Satellite Lightning Data

Nitrogen oxides(NOx;NO+NO2),controlling the concentration of O3 and OH,are trace gases important in atmospheric chemistry and climate change.NOx in the upper troposphere is mainly generated by lightning,however,the uncertainty of the amount of lightning-generated nitrogen oxides(LNOx)is the greatest.Up to now,foreign countries have carried out a lot of related researches.However,there are few relevant studies in China,and different researchers use different estimation methods to obtain the results which range large(0.016-0.38 Tg(N)/y).It is therefore of great importance to further discuss the estimation methods and results of LNOx in China.This paper uses the peak current of lightning in the cloud-to-ground lightning(CG)location data to estimate the energy generated by each CG.In combination with the formula of intracloud lightning(IC)to CG ratio in the literature,the spatial and temporal distribution characteristics of lightning and lightning-generated NO(LNO)and the average annual output of LNOx are estimated in China continental area.Using satellite data and according to the empirical formula to distinguish IC and total CG,and based on the ratio of the positive and negative CG to total CG estimated from the CG location data to distinguish positive and negative CG.Combined with the production of a single IC NO and a single CG NO in the literature,the spatial and temporal distribution characteristics of lightning and LNO and the average annual output of LNOx are also estimated in China continental area.Through these two estimation methods,the main conclusions are as follows:(1)The seasonal spatial distribution of LNO amount is basically consistent with that of lightning frequencies and number of lightning return strokes,but contrary to the peak currents of lightning.This indicates that the LNO amount is mainly affected by the lightning number and the number of lightning return strokes,rather than the lightning peak currents.The amount of NO produced by negative CG is the largest,followed by IC,and the amount of positive CG is the smallest(2)On average,the positive CG generally has only one stroke,the negative CG has multiple strokes.However,the peak current of a single positive CG is larger,and the energy accumulated by a single positive CG is larger than that of a single negative CG,thus producing more NO.Therefore,the ratio of positive CG NO to total LNO is higher than that of positive CG to CG(3)The distribution characteristics of LNO estimated by satellite combined CG data are similar to those only based on CG data,however,both in the regions with the highest lightning density(coastal areas)and in regions with the lower lightning density(northeast China,north China,parts of southwest China and northwest Xinjiang),the former are larger than the latter.(4)The LNOx amount in China continental area estimated only by CG data vary between 0.286 and 0.617(Tg(N)/y).This is in good agreement with the estimations of 0.81(Tg(N)/y)which base on CG location data combined with satellite lightning data(5)This value from China in China continental area as an average for global values,which means globally LNOx is between 4.44-12.5 Tg(N)/y,which is on the high side of currently estimations(2-8 Tg(N)/y).