Impact of future supersonic aircraft on the distribution of stratospheric tracers: Chemical and dynamical perturbations

Abstract

Impact studies of future supersonic aircraft (HSCT) are normally made using two- or three- dimensional chemical transport models (CTM). In this case the calculated ozone profile and column changes result from perturbed efficiencies of the catalytic cycles for O 3 depletion (NO x , HO x , Cl x , Br x ): radical species changes are produced by aircraft emissions of NO x , water vapour and sulphur. On the other hand, steady state accumulation of H 2 O from HSCT can produce significant anomalies in the lower stratospheric water vapour mixing ratio (about 10% at Northern mid-latitudes). Stratospheric H 2 O and O 3 absorb longwave planetary radiation, so that HSCT driven changes may up-set the residual circulation in the lower stratosphere. In this work results are presented from a climate-chemistry coupled model, taking into account both HSCT driven photochemical changes and also dynamical anomalies produced by perturbed ozone and water vapour accumulation. The major conclusions are the following: (a) H 2 O accumulation patterns change significantly in the tropical lower stratosphere, with respect to the case with no radiative feedback on circulation of HSCT additional H 2 O and perturbed O 3 . The tropopause radiative forcing of this additional water vapour is greatly reduced with respect to the fixed circulation case. (b) Lower stratospheric vertical fluxes of H 2 O and other atmospheric tracers are significantly affected by water vapour and ozone radiative feedback on the stratospheric circulation. (c) Dynamically driven ozone changes dominate in magnitude over chemically produced ones.