The effects of lightning-produced NO_x and its vertical distribution on atmospheric chemistry: sensitivity simulations with MATCH-MPIC

Abstract. The impact of different assumptions concerning the source magnitude as well as the vertical placement of lightning-produced nitrogen oxides is studied using the global chemistry transport model MATCH-MPIC. The responses of NO_x, O₃, OH, HNO₃ and peroxyacetyl-nitrate (PAN) are investigated. A marked sensitivity to both parameters is found. NO_x burdens globally can be enhanced by up to 100% depending on the vertical placement and source magnitude strength. In all cases, the largest enhancements occur in the tropical upper troposphere, where lifetimes of most trace gases are longer and where they thus become more susceptible to long-range transport by large-scale circulation patterns. Comparison with observations indicate that 0 and 20 Tg(N)/yr production rates of NO_x from lightning are too low and too high, respectively. However, no single intermediate production rate or vertical distribution can be singled out as best fitting the observations, due to the large scatter in the datasets. This underscores the need for further measurement campaigns in key regions, such as the tropical continents.