Comments on the parameterization of lightning-produced NO in global chemistry-transport models

Many current global chemistry-transport models limit the annual global source strength of reactive nitrogen from lightning activity to 5 Tg N yr−1. However, there is strong evidence from aircraft and cloud-resolving model studies and theory that production of NO by an intracloud flash is not an order of magnitude smaller than from a cloud-to-ground flash, an assumption commonly used in the global models. We suggest that modification of the global models to accept comparable production of NO by both types of discharge and the necessarily larger input of NO to higher altitudes will require a reduction in their global annual source strength from lightning activity in order to match existing observations.