Lightning NO_x Emissions: Reconciling Measured and Modeled Estimates With Updated NO_x Chemistry

Abstract

Lightning is one of the most important sources of upper tropospheric NO_x; however, there is a large spread in estimates of the global emission rates (2–8 Tg N yr^(−1)). We combine upper tropospheric in situ observations from the Deep Convective Clouds and Chemistry (DC3) experiment and global satellite-retrieved NO_2 tropospheric column densities to constrain mean lightning NO_x (LNO_x) emissions per flash. Insights from DC3 indicate that the NO_x lifetime is ~3 h in the region of outflow of thunderstorms, mainly due to production of methyl peroxy nitrate and alkyl and multifunctional nitrates. The lifetime then increases farther downwind from the region of outflow. Reinterpreting previous analyses using the 3 h lifetime reduces the spread among various methods that have been used to calculate mean LNO_x emissions per flash and indicates a global LNO_x emission rate of ~9 Tg N yr^(−1), a flux larger than the high end of recent estimates.

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