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

Kurzfassung

. 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 %.