Sensitivity of climate–chemistry model simulated atmospheric composition to the application of an inverse relationship between NOx emission and lightning flash frequency

Abstract

Lightning-produced nitrogen oxides (LNOx = LNO + LNO2) are an important source of upper-tropospheric ozone. Typical parameterizations of LNOx in climate–chemistry models introduce a constant amount of NOx per flash or per flash type. However, recent satellite-based NO2 measurements suggest that the production of LNOx per flash depends on the lightning flash frequency. In this study, we implement a new parameterization of LNOx production per flash based on the lightning flash frequency in a climate–chemistry model to investigate the upper-limit implications for the chemical composition of the atmosphere. We find that a larger production of LNOx in weak thunderstorms leads to a larger mixing ratio of NOx in the lower and middle troposphere, as well as to a lower mixing ratio of NOx in the upper troposphere. The mixing ratios of O3, CO, HOx, HNO3, and HNO4 in the troposphere are influenced by the simulated changes in LNOx. Our findings indicate a larger release of nitrogen oxides from lightning in the lower and middle atmosphere, producing a slightly better agreement with the measurements of tropospheric ozone at a global scale. In turn, we obtain a small decrease in the lifetime of methane and carbon monoxide, ranging between 0.7 % and 3.4 %.