Do supersonic aircraft avoid contrails?

Abstract

Abstract. The impact of a potential future fleet of supersonic aircraft on contrail coverage and contrail radiative forcing is investigated by means of simulations with the general circulation model ECHAM4.L39(DLR) including a contrail parameterization. The model simulations consider air traffic inventories of a subsonic fleet and of a combined fleet of suband supersonic aircraft for the years 2025 and 2050, respectively. In case of the combined fleet, part of the subsonic fleet is replaced by supersonic aircraft. The combined air traffic scenario reveals a reduction in contrail cover at subsonic cruise levels (10 to 12 km) in the northern extratropics, especially over the North Atlantic and North Pacific. At supersonic flight levels (18 to 20 km), contrail formation is mainly restricted to tropical regions. Only in winter is the northern extratropical stratosphere above the 100 hPa level cold enough for the formation of contrails. Total contrail coverage is only marginally affected by the shift in flight altitude. The model simulations indicate a global annual mean contrail cover of 0.372% for the subsonic and 0.366% for the combined fleet in 2050. The simulated contrail radiative forcing is most closely correlated to the total contrail cover, although contrails in the tropical lower stratosphere are found to be optically thinner than contrails in the extratropical upper troposphere. The global annual mean contrail radiative forcing in 2050 (2025) amounts to 24.7 mW m −2 (9.4 mW m −2 ) for the subsonic fleet and 24.2 mW m −2 (9.3 mW m −2 ) for the combined fleet. A reduction of the supersonic cruise speed from Mach 2.0 to Mach 1.6 leads to a downward shift in contrail cover, but does not affect global mean total contrail cover and contrail radiative forcing. Hence the partial substitution of subsonic air traffic leads to a shift of contrail occurrence from mid to low latitudes, but the resulting change in contrail-induced climate impact is almost negligible.

Radiative forcing from particle emissions by future supersonic aircraft

“…It should be noted that if not specified otherwise, for the remainder of the paper we refer to scenario S6 as the reference case. Fuel consumption and NO x emission indices for the future projected subsonic fleet in the SCENIC scenarios (Grewe and Stenke, 2008). This means that the SCENIC projected average increase of fuel use is about 3.4% up to 2025 and 2.8% up to 2050, both consistent with the 3% estimate in IPCC (1999), taking into account the projected greater efficiency of future aircraft.…”

AirClim: an efficient tool for climate evaluation of aircraft technology

“…Mean values for emission strengths of 125 and 0.45×10 −15 kg/kg/s are chosen to represent these ranges (Table 3), respectively. (Hein et al, 2001), in which we accounted for full Lagrangian transport (ATTILA, Reithmeier and Sausen, 2002) of all species including water vapour and cloud water, which significantly improves the representation of stratospheric water vapour and temperatures (Stenke et al, 2008a). E39/C consists of the troposphere-stratosphere climate model ECHAM4.L39(DLR) (E39, Land et al, 1999) and the troposphere-stratosphere chemistry module CHEM (Steil et al, 1998).…”

“…It could be included by a simple off-set factor to linear shaped contrails. However, since best estimates on the ratio between the climate impact of cirrus-contrails and lineshaped contrails are not available, we have disregarded the contrail-cirrus effect, which is regarded to be a minor source of uncertainty with respect to a partial replacement of subsonic by supersonic aircraft (Stenke et al, 2008a (Stuber et al, 2001;Joshi et al, 2003). This relationship is expressed in terms of climate sensitivity, i.e.…”

“…Concerning methane, Sausen et al (2005) as well as IPCC (1999) assumes steady-state perturbation to obtain the methane changes associated radiative forcing whereas in AirClim a lifetime change based on OH changes is estimated, which would become fully effective only after more Contrail radiative forcing agrees within 20%, though, the underlying emission data sets differ (DLR-2 aircraft emission dataset used in the study by Marquart et al (2003)), which inhibits a constrained verification of the linearisation approach. A direct intercomparison with the detailed modelling results obtained by Stenke et al (2008a) can be performed. They calculated a contrail coverage of 0.372% for the SCENIC S4 subsonic fleet in 2050 and a associated radiative forcing of 24.7 mW m 2 .…”

Climate impact of supersonic air traffic: an approach to optimize a potential future supersonic fleet – results from the EU-project SCENIC

“…Physc. Discuss., in preparation, 2007. companion papers (Stenke et al, 2007a;Søvde et al, 2007;Pitari et al, 2007 2 ) and is thought to serve as an input and basis for the climate change calculation (Sect. 5.3) via an estimate of radiative forcing (Sect.…”