Radiative forcing from particle emissions by future supersonic aircraft

In this work we focus on the direct radiative forc- ing (RF) of black carbon (BC) and sulphuric acid particles emitted by future supersonic aircraft, as well as on the ozone RF due to changes produced by emissions of both gas species (NOx, H2O) and aerosol particles capable of affecting strato- spheric ozone chemistry. Heterogeneous chemical reactions on the surface of sulphuric acid stratospheric particles (SSA- SAD) are the main link between ozone chemistry and su- personic aircraft emissions of sulphur precursors (SO 2) and particles (H2O-H2SO4). Photochemical O3 changes are compared from four independent 3-D atmosphere-chemistry models (ACMs), using as input the perturbation of SSA-SAD calculated in the University of L'Aquila model, which in- cludes on-line a microphysics code for aerosol formation and growth. The ACMs in this study use aircraft emission scenar- ios for the year 2050 developed by AIRBUS as a part of the EU project SCENIC, assessing options for fleet size, engine technology (NOx emission index), Mach number, range and cruising altitude. From our baseline modeling simulation, the impact of supersonic aircraft on sulphuric acid aerosol and BC mass burdens is 53 and 1.5µg/m 2 , respectively, with a direct RF of 11.4 and 4.6 mW/m 2 (net RF= 6.8 mW/m 2 ). This paper discusses the similarities and differences amongst the participating models in terms of changes to O3 precursors due to aircraft emissions (NOx, HOx ,Clx ,Brx ) and the strato- spheric ozone sensitivity to them. In the baseline case, the calculated global ozone change is 0.4 ±0.3 DU, with a net radiative forcing (IR+UV) of 2.5± 2 mW/m 2 . The fraction