Stratospheric ozone and climate forcing sensitivity to cruise altitudes for fleets of potential supersonic transport aircraft

The possibility of commercial and business supersonic aircraft that fly in the lower stratosphere is being discussed and specific designs are under consideration. Emissions from supersonic transports have raised crucial environmental concerns regarding ozone and climate. The atmospheric response is sensitive to a range of factors regarding aircraft types, designs, and deployment parameters. This study conducts a series of sensitivity experiments of possible future cruise altitudes to evaluate the potential atmospheric response for a fleet of supersonic aircraft assumed to be fully operational in 2050. Cruise emissions in the sensitivity studies were varied in 2 km bands over the 13-23 km altitude range. We show that the supersonic aircraft can induce both ozone increase and decrease depending on altitude primarily as a result of emissions of nitrogen oxides, and the changes in total column ozone depend on the cruise altitude. The total column ozone change is shown to have a small increase flying from 13 to 17 km, with the ozone impact not very dependent on cruise altitude. As cruise altitude transitions from 17 to 23 km, the ozone impact transitions from production to depletion and the column ozone depletion strongly depends on cruise altitude. We also explore the seasonal ozone loss, changes in ozone, and climate radiative forcing per unit of fuel burn as a function of cruise altitude. The climate impact of water vapor emissions shows a larger effect associated with higher cruise altitude, with more than 1 mW m(-2) Tg(-1) yr for cruise altitudes above 19 km.