Global NOx production by lightning

Lightning is thought to represent an important source of tropospheric reactive nitrogen species NOx (NO + NO2), but estimates of global production of NOx by lightning vary considerably. We evaluate the production of NOx by lightning using a global chemical/transport model, satellite lightning observations, and airborne NOx measurements. Various model calculations are conducted to assess the global NOx production rate of lightning by comparing the model calculations with airborne measurements. The results show that the simulated NOx in the tropical middle and upper troposphere are very sensitive to the amount and altitude of the lightning NOx used in the model. A global lightning NOx production of 7 Tg N yr(-1) uniformly distributed in convective clouds or 3.5 Tg N yr(-1) distributed in the upper cloud regions produces good agreement between calculated and measured NOx concentrations in the tropics.