Role of Lightning NOx in Ozone Formation: A Review

This paper provides an overview on the spatiotemporal distribution and evolution mechanism of lightning. The predominant mechanism of ozone formation in the upper troposphere is lightning-induced precursors such as oxides of nitrogen (NOx), carbon monoxide (CO), and hydrocarbons (HC). Lightning-induced NOx (LNOx) is one of the major ordinary sources of NOx in the upper atmosphere, particularly in the tropical region, but it is still highly uncertain as to the exact quantity. Various ground measurements, satellite observations and modelling studies on the lightning and global NOx source rate have been extensively studied and compared to find the variability in estimated global lightning-induced NOx. Lightning can influence the climate via the production of nitrogen oxides (NO + NO 2 = NOx) followed by the production of ozone, another efficient greenhouse gas. The global annual lightning NOx of 5 ± 3 Tg year −1 has been estimated by modelling studies with an ozone creation efficiency of 6.5 ± 4.7 times that of surface NOx sources. Understanding and quantifying the processes and production of lightning and LNOx is important for assessment of ozone concentrations and its associated impacts on the global climate.