Identifying the ozone-neutral aircraft cruise altitude. (1st May 2022)

• Record Type: Journal Article
• Authors: Fritz, Thibaud M.; Dedoussi, Irene C.; Eastham, Sebastian D.; Speth, Raymond L.; Henze, Daven K.; Barrett, Steven R.H.
• Is Part Of: Atmospheric environment. Volume 276(2022)
• Publication Date: 2022-05-01
• Subjects: Ozone depletion -- Stratospheric chemistry -- Supersonic aviation -- Adjoint modeling; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2022.119057
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Depletion of stratospheric ozone, and the associated increase in population exposure to UV radiation, is an environmental consequence of high-altitude, supersonic aviation. Assessments of the impacts of emissions from subsonic aircraft – which fly at lower altitudes – have instead shown that they produce a net increase, rather than decrease, in global net ozone, suggesting the existence of an intermediate "column ozone neutral" cruise altitude. Knowing this altitude and its variation with factors such as latitude, season, and fuel composition could provide a pathway towards reducing the environmental impacts of aviation, but would require a prohibitive number of atmospheric simulations. We instead use the newly developed GEOS-Chem tropospheric-stratospheric adjoint to identify the location of the column ozone-neutral aircraft cruise altitude as a function of these factors. We show that, although the mean ozone neutral altitude is at 13.5 km globally, this varies from 14.6 km to 12.5 km between the equator and 60°N. This altitude varies by less than a kilometer between seasons, but the net depletion resulting from flying at greater altitudes varies by a factor of two. We also find that eliminating fuel sulfur would result in a neutral altitude 0.5–1.0 km greater than when conventional jet fuel is burned. Our results imply that a low Mach number supersonic aircraft burning low-sulfur fuel (e.g. biofuels) may be able to achieve net zero global ozone change. However, for a fleet to achieve ozone neutrality will require careful consideration of the non-linear variation in sensitivity with altitude and latitude. Highlights: We use adjoint methods to calculate ozone loss resulting from flights at any altitude. We find that ozone depletion from aircraft depends non-linearly on flight altitude. Supersonic aircraft are likely to cause significant ozone depletion. Flight at 13–14 km altitude could be "ozone neutral". Inclusion of sulfur in fuel may increase this altitude by 0.5–1.0 km.