Temporal And Spatial Characteristics Of Lightning-produced Nitrogen Oxides In China

Tropospheric NO2 vertical column densities (NO2VCDs) retrieved from the Global Ozone Monitoring Experiment-2 satellite spectrometer, as well as lightning flashes measured by an Optical Transient Detector and Lightning Image Sensor from 1997 to 2013 are used to investigate spatial and temporal characteristics of lightning-produced nitrogen oxides (LNOx) under the recent period of rapid and locally-unbalanced economic development in China. Correlations between spatial distributions of lightning flashes and monthly mean tropospheric NO2VCDs were analyzed over this period. Mean production of LNOx per flash is 330mol[N]/flash which was estimated using the correlation between lightning flashes and monthly mean tropospheric NO2VCD for the Tibetan Plateau. Using this correlation, the spatial and temporal characteristics of the ratio of LNOx to tropospheric NOx in China were determined. Results show that the ratio of LNOx to the tropospheric NOx is small in eastern regions, having a developed industrial sector and dense population,but relatively large in western regions,with a developing industrial sector and sparser population. The annual mean value of LNOx contributing to tropospheric NOx is 7.8% in China, which is at a low value comparing to the global averages(10-20%). The difference in interannual variability of LNOx production contributing to tropospheric NOx in different areas is distinct, ranging from high to low values for the Tibetan Plateau, Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei regions, respectively. This indicates that lightning had a large influence on the column density of tropospheric NOx on the Tibetan Plateau, a region typically used as a sensitivity indicator for climate change. Lightning had less influence on atmospheric environments of the Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei regions.In different regions and seasons,the proportion of LNOx accounted for the total NOx in the troposphere is also different.On the whole,the Tibet Plateau is spring (summer) > autumn > winter, and the other three areas are summer > spring > autumn > winter. At the same time, the effects of the El Nino year(1997/1998) and the normal year (2001/2004) lightning and NOx in China are analyzed. And the typical eastern and western regions of China were selected to further study the correlation between lightning and N02 in the period of El Nino in China, and further analyze the influence of LNOx on atmospheric environment.Studies have shown that El Nino events in the 1997/1998 weakened the central and Western lightning and strengthened the southeastern region of China, while weakening China's summer lightning and increasing the lightning in autumn and winter. This is of great significance to further clarify the impact of lightning on China's climate and environment.