Strong sensitivity of the global mean OH concentration and the tropospheric oxidizing efficiency to the source of NOx from lightning -: art. no. L06102

Production of nitrogen oxides (NOx = NO + NO2) by lightning (LtNO(x)) is the most uncertain among the global NOx sources, with recent estimates ranging from about 1 20 Tg(N)/yr. Previous studies of LtNO(x) have focused mainly on its role in the tropospheric NOy (reactive nitrogen) and O-3 budgets. We show that the global mean OH concentration is also very sensitive to LtNO(x). Furthermore, despite the fact that the largest changes in NOx due to lightning are in the upper troposphere, where reactions with OH are generally slower, we find that the sensitivity of the mean tropospheric lifetime of methane (CH4) and methylchloroform (CH3CCl3) to assumptions about LtNO(x) are as large as the sensitivity of the tropospheric O-3 burden. Thus, an improved understanding of LtNO(x) will be important for our ability to accurately simulate the tropospheric oxidizing efficiency and its changes over time.