Radiative forcing from particle emissions by future supersonic aircraft

Abstract

Abstract. In this work we focus on the direct radiative forcing (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 (NO x , H 2 O) and aerosol particles capable of affecting stratospheric ozone chemistry. Heterogeneous chemical reactions on the surface of sulphuric acid stratospheric particles (SSA-SAD) are the main link between ozone chemistry and supersonic aircraft emissions of sulphur precursors (SO 2 ) and particles (H 2 O-H 2 SO 4 ). Photochemical O 3 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 includes on-line a microphysics code for aerosol formation and growth. The ACMs in this study use aircraft emission scenarios for the year 2050 developed by AIRBUS as a part of the EU project SCENIC, assessing options for fleet size, engine technology (NO x 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 1.5 µg/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 O 3 precursors due to aircraft emissions (NO x , HO x ,Cl x ,Br x ) and the stratospheric 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 Correspondence to: G. Pitari (gianni.pitari@aquila.infn.it) of this O 3 -RF attributable to SSA-SAD changes is, however, highly variable among the models, depending on the NO x removal efficiency from the aircraft emission regions by large scale transport.

Impacts of a near-future supersonic aircraft fleet on atmospheric composition and climate

“…1–6 Studies have also quantified climate impacts associated with supersonic aircraft including radiative forcing due to CO 2 , water vapor, and changes in ozone. 2,6–12…”

“…2 A study by Rahmes et al focused on soot, finding a radiative forcing of less than 1 mW m −2 from supersonic aircraft black carbon emissions burning 77 Tg of fuel year. 21 However, a later study of supersonic aviation's impacts by Grewe et al under the European Union SCENIC project found radiative forcings from emitted black carbon and sulfur aerosols of +4.6 mW m −2 and −11.4 mW m −2 respectively for an annual fuel burn of 60 Tg, exceeding the radiative forcing from either CO 2 emissions or changes in ozone despite the use of a black carbon emissions index 75% lower than that used by Rahmes et al 7,11 The presence or absence of fuel sulfur has also been found to significantly change the total ozone depletion resulting from supersonic aviation. Based on 2-D simulations, Weisenstein et al found that a fuel sulfur content of 200 ppm by mass could make sulfur emissions “potentially more important than emissions of NO x and H 2 O in terms of ozone depletion”.…”

Impact of Coupled NOx/Aerosol Aircraft Emissions on Ozone Photochemistry and Radiative Forcing

“…The emissions also increase the size of pre-existing sulphuric acid aerosols, from the additional condensation of H2SO4 formed through OH oxidation of aircraft emitted SO2 [9,66]. The largest increase of the aerosol SAD comes from the newly formed [67], a 10% plume particle formation fraction and a 25% additional aircraft contribution to SAD from gas phase SO2 emissions, the Kärcher and Meilinger [17] calculation gives an aircraft SAD change of 0.37 μm 2 /cm 3 .…”

Review: The Effects of Supersonic Aviation on Ozone and Climate

“…In the short-wave regime, the dominant effect of sulphate aerosols is scattering, leading to a negative RF, whereas for BC, absorption dominates, leading to a positive RF. One modelling study with a course resolution including 144 horizontal grid cells on 26 vertical levels found an RF of 4.6 mW/m 2 and −11.4 mW/m 2 for BC and sulphate aerosols through supersonic aviation emissions, respectively, computed using the SCENIC replacement scenario [62] (Table 1). This study also investigated modified SCENIC scenarios which gave RFs ranging from 0.4 to 11.0 mW/m 2 for BC and −3.9 to −23.3 mW/m 2 for sulphate aerosols.…”

“…Previous studies have often omitted the indirect aerosol effects of supersonic aviation emissions, which are known to represent a large uncertainty [4]. One study found that the indirect aerosol RF is highly variable between models, mainly because of the different dynamics influencing the removal efficiency of NO x from the emission region [62]. However, as their model had to rely on very coarse spatial resolution and strongly parameterised aerosol dynamics processes, we do not include their results in this study.…”