Sensitivity of climate-chemistry model simulated atmospheric composition to lightning-produced NO_x parameterizations based on lightning frequency

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