Abstract
Abstract. Lineshaped contrails were detected with the research aircraft Falcon during the CONCERT – CONtrail and Cirrus ExpeRimenT – campaign in October/November 2008. The Falcon was equipped with a set of instruments to measure the particle size distribution, shape, extinction and chemical composition as well as trace gas mixing ratios of sulfur dioxide (SO2), reactive nitrogen and halogen species (NO, NOy, HNO3, HONO, HCl), ozone (O3) and carbon monoxide (CO). During 12 mission flights over Europe, numerous contrails, cirrus clouds and a volcanic aerosol layer were probed at altitudes between 8.5 and 11.6 km and at temperatures above 213 K. 22 contrails from 11 different aircraft were observed near and below ice saturation. The observed NO mixing ratios, ice crystal and soot number densities are compared to a process based contrail model. On 19 November 2008 the contrail from a CRJ-2 aircraft was penetrated in 10.1 km altitude at a temperature of 221 K. The contrail had mean ice crystal number densities of 125 cm−3 with effective radii reff of 2.6 μm. The presence of particles with r>50 μm in the less than 2 min old contrail suggests that natural cirrus crystals were entrained in the contrail. Mean HONO/NO (HONO/NOy) ratios of 0.037 (0.024) and the fuel sulfur conversion efficiency to H2SO4 (εS↓) of 2.9 % observed in the CRJ-2 contrail are in the range of previous measurements in the gaseous aircraft exhaust. On 31 October 2010 aviation NO emissions could have contributed by more than 40% to the regional scale NO levels in the mid-latitude lowest stratosphere. The CONCERT observations help to better quantify the climate impact from contrails and will be used to investigate the chemical processing of trace gases on contrails.
Highlights
While aircraft induced cloudiness potentially has the largest aviation impact on climate, the exact magnitude of its contribution to the anthropogenic radiative forcing remains highly uncertain (Lee et al, 2009)
When the ambient air remains supersaturated with respect to ice, the contrail ice crystals can grow by condensation of entrained water vapor (Schroder et al, 2000)
Contrail encounters are marked by fast simultaneous increases in the nitric oxide (NO) mixing ratio, the particle number density detected with the FSSP and the extinction detected with the Polar Nephelometer (PN)
Summary
While aircraft induced cloudiness potentially has the largest aviation impact on climate, the exact magnitude of its contribution to the anthropogenic radiative forcing remains highly uncertain (Lee et al, 2009). Mean effective radii of contrail ice crystals derived from in situ data show values below 2 μm initially (Heymsfield et al, 1998; Baumgardner and Gandrud, 1998), increasing due to condensation to values of up to 5 μm at 30 min contrail age (Schroder et al, 2000). In persistent contrails with ages of few hours, ice crystal concentrations of less than 20 cm−3 have been observed (Lawson et al, 1998; Schauble et al, 2009). At temperatures below 205 K, the gas phase HNO3 is significantly reduced due to uptake in contrail ice crystals as detected for the contrail of a WB-57 at 14 km altitude (Popp et al, 2004). We discuss the chemical processing of sulfur and halogens species in the aged volcanic plume and derive the e-folding lifetime of SO2 in the northern latitude lowest stratosphere
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