Contrail Formation: Analysis of Sublimation Mechanisms

Kärcher, B.; Kleine, Jonas; Sauer, Daniel; Voigt, Christiane

doi:10.1029/2018gl079391

Cited by 14 publications

(15 citation statements)

References 14 publications

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“…The presence of interstitial soot in the secondary wake might be a third explanation. However, since 96% of emitted soot particles nucleate ice particles in this contrail (Kärcher et al, ), this would imply the sublimation of part of the ice particles near Δz = 0. This, however, is inconsistent with measured ambient ice supersaturation at the ATRA flight altitude.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, they provide strong evidence that the contrail ice particles indeed nucleated on the emitted soot particles. We further analyze sublimation mechanisms and quantify the associated ice particle losses to predictions by means of a parameterization scheme for contrail ice formation that covers both, nucleation and sublimation phases, in the companion paper (Kärcher et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…As we will show, the data lend themselves to a self‐consistent interpretation of the microphysical pathway to contrail ice formation. We offer an in‐depth model‐data comparison in a separate study (Kärcher et al, ). While section outlines the airborne research campaign as well as the instrumentation employed and methods used to analyze the particle data, section presents and discusses the main results.…”

Section: Introductionmentioning

confidence: 99%

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In Situ Observations of Ice Particle Losses in a Young Persistent Contrail

Kleine

Voigt

Sauer

et al. 2018

Geophysical Research Letters

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We describe results of in situ observations of a 1‐ to 2‐min‐old contrail in the vortex phase generated from soot‐rich exhaust (>1015 emitted soot particles per kilogram of fuel burned). Simultaneous measurements of soot (EIsoot) and apparent ice (AEIice) particle number emission indices show a pronounced anticorrelation in the vertical contrail profile. AEIice decrease by about 75% with increasing distance below the contrail‐producing aircraft, while EIsoot increase by an equivalent relative fraction, therefore strongly suggesting ice particle formation to be soot‐controlled and losses to be caused by sublimation. Quantifying these losses in measurements helps to validate and improve contrail parameterizations used to estimate the climate impact of contrails and contrail cirrus. Our study further demonstrates the challenges in the performance and interpretation of particle measurements in young contrails and lends itself to suggestions for improving contrail data evaluation.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In Situ Observations of Ice Particle Losses in a Young Persistent Contrail

Kleine

Voigt

Sauer

et al. 2018

Geophysical Research Letters

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“…Contrails form behind an aircraft when the atmospheric conditions are favourable (high humidity and low temperatures) [1,2]. Black carbon (BC) particles and water vapour emitted from the exhaust of aircraft engines play a key role in this process [3,4]: hot aircraft exhaust mixes with cool ambient air causing an increase in relative humidity; liquid water droplets form on the surface of BC particles when the humidity in this mixture exceeds liquid saturation and these droplets then freeze into ice crystals.…”

Section: Introductionmentioning

confidence: 99%

Beyond Contrail Avoidance: Efficacy of Flight Altitude Changes to Minimise Contrail Climate Forcing

2020

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Contrail cirrus introduce a short-lived but significant climate forcing that could be mitigated by small changes in aircraft cruising altitudes. This paper extends a recent study to evaluate the efficacy of several vertical flight diversion strategies to mitigate contrail climate forcing, and estimates impacts to air traffic management (ATM). We use six one-week periods of flight track data in the airspace above Japan (between May 2012 and March 2013), and simulate contrails using the contrail cirrus prediction model (CoCiP). Previous studies have predominantly optimised a diversion of every contrail-forming flight to minimise its formation or radiative forcing. However, our results show that these strategies produce a suboptimal outcome because most contrails have a short lifetime, and some have a cooling effect. Instead, a strategy that reroutes 15.3% of flights to avoid long-lived warming contrails, while allowing for cooling contrails, reduces the contrail energy forcing (EFcontrail) by 105% [91.8, 125%] with a total fuel penalty of 0.70% [0.66, 0.73%]. A minimum EFtotal strategy (contrails + CO2), diverting 20.1% of flights, reduces the EFcontrail by the same magnitude but also reduces the total fuel consumption by 0.40% [0.31, 0.47%]. For the diversion strategies explored, between 9% and 14% of diversions lead to a loss of separation standards between flights, demonstrating a modest scale of ATM impacts. These results show that small changes in flight altitudes are an opportunity for aviation to significantly and rapidly reduce its effect on the climate.

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“…We spread 25 SIPs randomly in each vertical bin where contrail ice is present, yielding NSIP

= 3, 725

. The initial total contrail ice crystal number concentration is largest (100 cm

^{- 3}

t_{0} = 10

min) in the upper layer that is 50 m thick, decreasing exponentially downwards with a scale height of 100 m. The reduced number concentration in the lower contrail area accounts for sublimation losses that occur in aircraft wakes within the first few minutes past formation (Kärcher et al, ). The

n

profile represents a spatial average across the aircraft wake perpendicular to the flight direction.…”

Section: Model Applicationsmentioning

confidence: 99%

Process‐Based Simulation of Aerosol‐Cloud Interactions in a One‐Dimensional Cirrus Model

Kärcher¹

2020

JGR Atmospheres

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A new microphysical cirrus model to simulate ice crystal nucleation, depositional growth, and gravitational settling is described. The model tracks individual simulation ice particles in a vertical column of air and allows moisture and heat profiles to be affected by turbulent diffusion. Ice crystal size‐ and supersaturation‐dependent deposition coefficients are employed in a one‐dimensional model framework. This enables the detailed simulation of microphysical feedbacks influencing the outcome of ice nucleation processes in cirrus. The use of spheroidal water vapor fluxes enables the prediction of primary ice crystal shapes once microscopic models describing the vapor uptake on the surfaces of cirrus ice crystals are better constrained. Two applications addressing contrail evolution and cirrus formation demonstrate the potential of the model for advanced studies of aerosol‐cirrus interactions. It is shown that supersaturation in, and microphysical and optical properties of, cirrus are affected by variable deposition coefficients. Vertical variability in ice supersaturation, ice crystal sedimentation, and high turbulent diffusivity all tend to decrease homogeneously nucleated ice number mixing ratios over time, but low ice growth efficiencies counteract this tendency. Vertical mixing induces a tendency to delay the onset of homogeneous freezing. In situations of sustained large‐scale cooling, natural cirrus clouds may often form in air surrounding persistent contrails.

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Contrail Formation: Analysis of Sublimation Mechanisms

Cited by 14 publications

References 14 publications

In Situ Observations of Ice Particle Losses in a Young Persistent Contrail

In Situ Observations of Ice Particle Losses in a Young Persistent Contrail

Beyond Contrail Avoidance: Efficacy of Flight Altitude Changes to Minimise Contrail Climate Forcing

Process‐Based Simulation of Aerosol‐Cloud Interactions in a One‐Dimensional Cirrus Model

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