Temporal and spatial variability in the aviation NO[subscript x]-related O[subscript 3] impact

Abstract

Aviation NO[subscript x] emissions promote tropospheric ozone formation, which is linked to climate warming and adverse health effects. Modeling studies have quantified the relative impact of aviation NO[subscript x] on O[subscript 3] in large geographic regions. As these studies have applied forward modeling techniques, it has not been possible to attribute O[subscript 3] formation to individual flights. Here we apply the adjoint of the global chemistry–transport model GEOS-Chem to assess the temporal and spatial variability in O[subscript 3] production due to aviation NO[subscript x] emissions, which is the first application of an adjoint to this problem. We find that total aviation NO[subscript x] emitted in October causes 40% more O[subscript 3] than in April and that Pacific aviation emissions could cause 4–5 times more tropospheric O[subscript 3] per unit NO[subscript x] than European or North American emissions. Using this sensitivity approach, the O[subscript 3] burden attributable to 83 000 unique scheduled civil flights is computed individually. We find that the ten highest total O[subscript 3]-producing flights have origins or destinations in New Zealand or Australia. The top ranked O[subscript 3]-producing flights normalized by fuel burn cause 157 times more normalized O[subscript 3] formation than the bottom ranked ones. These results show significant spatial and temporal heterogeneity in environmental impacts of aviation NO[subscript x] emissions.