Numerical simulations of contrail-to-cirrus transition – Part 2: Impact of initial ice crystal number, radiation, stratification, secondary nucleation and layer depth

Abstract.A comprehensive general circulation model including ice supersaturation is used to estimate the climate impact of aviation induced contrails. The model uses a realistic aviation emissions inventory for 2006 to initiate contrails, and allows them to evolve consistently with the model hydrologic cycle.The radiative forcing from linear contrails is very sensitive to the diurnal cycle. For linear contrails, including the diurnal cycle of air traffic reduces the estimated radiative forcing by 29 %, and for contrail cirrus estimates, the radiative forcing is reduced by 25 %. Estimated global radiative forcing from linear contrails is 0.0031 ± 0.0005 Wm −2 . The linear contrail radiative forcing is found to exhibit a strong diurnal cycle. The contrail cirrus radiative forcing is less sensitive to the diurnal cycle of flights. The estimated global radiative forcing from contrail cirrus is 0.013 ± 0.01 Wm −2 . Over regions with the highest air traffic, the regional effect can be as large as 1 Wm −2 .

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“…Unterstrasser and Gierens (2010) (Fig. 1) showed that these two competing effects nearly cancel each other.…”

Section: Referencementioning

confidence: 90%

Simulated radiative forcing from contrails and contrail cirrus

Chen

Gettelman

2013

Atmos. Chem. Phys.

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“…The turbulent velocity accounts for the sub-grid scale turbulent dispersion via the TKE equation. The EULAG model has been extensively used for aviationrelated numerical modelling in the past (Unterstrasser et al, 2008;Unterstrasser and Gierens, 2010b;Jeßberger et al, 2013).…”

Section: Eulag-lcmmentioning

confidence: 99%

Dimension of aircraft exhaust plumes at cruise conditions: effect of wake vortices

et al. 2014

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Abstract. The dispersion of aircraft emissions during the vortex phase is studied using a 3-D LES model with Lagrangian particle tracking. The simulations start with a fully rolled-up vortex pair of a type B747/A340 airplane and the tracer centred around the vortex cores. The tracer dilution and plume extent is studied for a variety of ambient and aircraft parameters until aircraft-induced effects have ceased. For typical upper tropospheric conditions, the impact of stratification is more dominant compared to turbulence intensity or vertical wind shear. Moreover, the sensitivity to the initial tracer distribution was found to be weak. Along the transverse direction, the tracer concentrations can be well approximated by a Gaussian distribution, along the vertical a superposition of three Gaussian distributions is adequate. For the studied parameter range, the vertical plume expansion ranges from 400 m to 550 m and cross-sectional area from 4.0 × 10 4 m 2 to 6 × 10 4 m 2 after six minutes. For validation, selected simulations were compared to an alternative LES model and to in-situ NO-measurements.

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“…Microphysical properties of contrails depend a lot more on the number of ice crystals than on the ice mass after the vortex phase (Unterstrasser and Gierens, 2010b). Therefore, it is appropriate to explicitly prescribe an initial ice crystal number concentration instead of an initial ice mass.…”

Section: Initial Values For Contrailsmentioning

confidence: 99%

Contrails and Their Impact on Shortwave Radiation and Photovoltaic Power Production – A Regional Model Study

Gruber¹,

Unterstraßer²,

Bechtold³

et al. 2017

Preprint

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Abstract. A high resolution regional-scale numerical model was extended by a parameterization that allows for both the generation and the life cycle of contrails and contrail cirrus to be calculated. The life cycle of contrails and contrail cirrus is described by a two-moment cloud microphysical scheme that was extended by a separate contrail ice class for a better representation of the high concentration of small ice crystals that occur in contrails. The basic input data set contains the spatially and temporally highly resolved flight trajectories over Central Europe derived from real time data. The parameterization provides 5 aircraft-dependent source terms for contrail ice mass and number. A case study was performed to investigate the influence of contrails and contrail cirrus on the radiative fluxes at the earth's surface. Accounting for contrails produced by aircraft enabled the model to simulate high clouds that were otherwise missing on this day. The effect of these extra clouds was to reduce the incoming shortwave radiation at the surface as well as the production of photovoltaic power by up to 10 %.

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Numerical simulations of contrail-to-cirrus transition – Part 2: Impact of initial ice crystal number, radiation, stratification, secondary nucleation and layer depth

Cited by 60 publications

References 28 publications

Simulated radiative forcing from contrails and contrail cirrus

Simulated radiative forcing from contrails and contrail cirrus

Dimension of aircraft exhaust plumes at cruise conditions: effect of wake vortices

Contrails and Their Impact on Shortwave Radiation and Photovoltaic Power Production – A Regional Model Study

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