Simulating the global atmospheric black carbon cycle: a revisit to the contribution of aircraft emissions

Abstract

Abstract. The black carbon (BC) burden of the upper troposphere and lowermost stratosphere (UTLS) is investigated with the general circulation model (GCM) ECHAM4. The special focus is the contribution of aircraft emissions to the UTLS BC loading. Previous studies on the role of aircraft emissions in the global BC cycle either neglect BC sources located at the Earth's surface or simplify the BC cycle by assuming pre-defined BC residence times. Here, the global BC cycle including emissions, transport, and removal is explicitly simulated. The BC emissions considered include surface sources as well as BC from aviation. This enables a consistent calculation of the relative contribution of aviation to the global atmospheric BC cycle. As a further extension to the previous studies, the aviation-induced perturbation of the UTLS BC particle number concentration is investigated. The uncertainties associated with the model predictions are evaluated by means of several sensitivity studies. Especially, the sensitivity of the results to different assumptions on the BC hygroscopic properties is analysed. The simulated UTLS BC concentrations are compared to in-situ observations. The simulations suggest that the large-scale contribution of aviation to the UTLS BC mass budget typically amounts to only a few percent, even in the most frequented flight regions. The aviation impact far away from these regions is negligible. The simulated aircraft contributions to the UTLS BC particle number concentration are much larger compared to the corresponding mass perturbations. The simulations suggest that aviation can cause large-scale increases in the UTLS BC particle number concentration of more than 30% in regions highly frequented by aircraft. The relative effect shows a pronounced annual variation with the largest relative aviation impact occurring during winter.

The global impact of the transport sectors on atmospheric aerosol: simulations for year 2000 emissions

“…The simulations reveal that aviation emissions can induce increases in the mean particle number concentration of 10-30 % at the main flight altitudes in the Northern Hemisphere. These perturbations are larger than for the mass concentration, due to small-sized particles, in agreement with the findings of previous studies (e.g., Hendricks et al, 2004). The simulated number concentration impacts are more sensitive to the assumed fuel sulfur content than to the choice of size distributions characterizing the emitted particle population.…”

“…The age of the observed plume was less than 1 s. The measured size distribution includes an Aitken mode, composed of primary BC particles with a median diameter of 25 nm, and an accumulation mode of larger particles (150 nm). For aircraft-generated BC particles, a vertical variation of the number-to-mass ratio (Hendricks et al, 2004) is additionally assumed. The fuel sulfur content during the P99 experiment was very low (2.6 mg(S) kg Lee et al, 2010).…”

Modeling the present and future impact of aviation on climate: an AOGCM approach with online coupled chemistry

“…Thus the number concentration of BC is significantly perturbed by aviation (Hendricks et al, 2004). The RF estimates for BC recently given by Balkanski et al (2010), are 0.1 or 0.3 mW m −2 , depending on whether the considered BC is externally or internally mixed with sulphate.…”

Atmospheric Aerosols: Composition, Transformation, Climate and Health Effects

“…[63][64][65] Despite a long tradition of soot and aerosol research, however, there is still no universally accepted and applied operational definition of BC and EC. Several studies have compared the different optical and thermal methods applied by atmospheric research groups to measure BC and EC.…”