Analytical treatment of ice sublimation and test of sublimation parameterisations in two–moment ice microphysics models

Gierens, Klaus; Bretl, Sebastian

doi:10.5194/acp-9-7481-2009

Cited by 10 publications

(14 citation statements)

References 11 publications

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“…If the ice size distribution would be narrow and if the plume is well mixed, then it seems conceivable that the number of ice particles stays constant until all ice mass is sublimated, when all particles disappear suddenly. However, this is not realistic (Gierens and Bretl, 2009). While growth of particles would narrow the size distribution, turbulent mixing of cloud air masses with particles of different sizes tends to broaden the size distribution.…”

Section: Contrail Lifetime and Ice Number Integrationmentioning

confidence: 95%

“…(13). In principle, ice mass and ice number evolve differently (Gierens and Bretl, 2009) implying different survival factors. Therefore, we cannot exclude at this stage that smaller survival factors might give better results.…”

Section: Initial Contrail Ice Crystal Number Concentrationmentioning

confidence: 99%

“…The models used are mainly based on dimensional analysis. The modeled loss processes are designed to simulate (turb:) particle losses by plume-internal turbulence, (agg:) sedimentation-induced aggregation (Sölch and Kärcher, 2010), and (meso:) losses induced by turbulent humidity fluctuations by mesoscale turbulence and gravity waves (Kärcher and Ström, 2003) and possibly plume turbulence (Gierens and Bretl, 2009;Unterstrasser and Gierens, 2010a). Also radiative heating of the contrail plume and of individual (large) ice particles may contribute to particle losses (Gierens, 1994;Chlond, 1998;Jensen et al, 1998a;Dobbie and Jonas, 2001;Unterstrasser and Gierens, 2010b).…”

Section: Contrail Lifetime and Ice Number Integrationmentioning

confidence: 99%

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A contrail cirrus prediction model

2012

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Abstract.A new model to simulate and predict the properties of a large ensemble of contrails as a function of given air traffic and meteorology is described. The model is designed for approximate prediction of contrail cirrus cover and analysis of contrail climate impact, e.g. within aviation system optimization processes. The model simulates the full contrail life-cycle. Contrail segments form between waypoints of individual aircraft tracks in sufficiently cold and humid air masses. The initial contrail properties depend on the aircraft. The advection and evolution of the contrails is followed with a Lagrangian Gaussian plume model. Mixing and bulk cloud processes are treated quasi analytically or with an effective numerical scheme. Contrails disappear when the bulk ice content is sublimating or precipitating. The model has been implemented in a "Contrail Cirrus Prediction Tool" (CoCiP). This paper describes the model assumptions, the equations for individual contrails, and the analysis-method for contrailcirrus cover derived from the optical depth of the ensemble of contrails and background cirrus. The model has been applied for a case study and compared to the results of other models and in-situ contrail measurements. The simple model reproduces a considerable part of observed contrail properties. Mid-aged contrails provide the largest contributions to the product of optical depth and contrail width, important for climate impact.

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Section: Contrail Lifetime and Ice Number Integrationmentioning

confidence: 95%

Section: Initial Contrail Ice Crystal Number Concentrationmentioning

confidence: 99%

Section: Contrail Lifetime and Ice Number Integrationmentioning

confidence: 99%

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A contrail cirrus prediction model

2012

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“…Gierens and Bretl (2009) explain it: Turbulent fluctuations lead to 5%-super/subsaturations in an on average saturated region inside the contrail. This leads to small oscillations in IWC, however the effect on N is more lasting.…”

Section: Total Ice Crystal Numbermentioning

confidence: 97%

Numerical simulations of contrail-to-cirrus transition – Part 1: An extensive parametric study

Unterstraßer

Gierens

2010

Atmos. Chem. Phys.

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Abstract.Simulations of contrail-to-cirrus transition over up to 6 h were performed using a LES-model. The sensitivity of microphysical, optical and geometric contrail properties to relative humidity RH i , temperature T and vertical wind shear s was investigated in an extensive parametric study. The dominant parameter for contrail evolution is relative humidity. Substantial spreading is only visible for RH i 120%. Vertical wind shear has a smaller effect on optical properties than human observers might expect from the visual impression. Our model shows that after a few hours the water vapour removed by falling ice crystals from the contrail layer can be several times higher than the ice mass that is actually present in the contrail at any instance.

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“…We attributed this to the differing microphysical treatment of the sublimation process on the fraction of surviving crystals. Gierens and Bretl (2009) discuss the sublimation parametrisation issue in two-moment bulk models. Testing the sublimation parametrisation against an analytical solution of the growth equation they found that there is no unique function relating crystal loss to mass loss.…”

Section: Discussionmentioning

confidence: 99%

Study of contrail microphysics in the vortex phase with a Lagrangian particle tracking model

Unterstraßer

Sölch

2010

Atmos. Chem. Phys.

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Abstract.Crystal sublimation/loss is a dominant feature of the contrail evolution during the vortex phase and has a substantial impact on the later contrail-to-cirrus transition. Previous studies showed that the fraction of crystals surviving the vortex phase depends primarily on relative humidity, temperature and the aircraft type. An existing model for contrail vortex phase simulations (with a 2-moment bulk microphysics scheme) was upgraded with a newly developed state-of-the-art microphysics module (LCM) which uses Lagrangian particle tracking. This allows for explicit processoriented modelling of the ice crystal size distribution in contrast to the bulk approach. We show that it is of great importance to employ an advanced microphysics scheme to determine the crystal loss during the vortex phase. The LCMmodel shows even larger sensitivities to the above mentioned key parameters than previously estimated with the bulk model. The impact of the initial crystal number is studied and for the first time also the initial width of the crystal size distribution. Both are shown to be relevant. This corroborates the need for a realistic representation of microphysical processes and knowledge of the ice phase characteristics.

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Analytical treatment of ice sublimation and test of sublimation parameterisations in two–moment ice microphysics models

Cited by 10 publications

References 11 publications

A contrail cirrus prediction model

A contrail cirrus prediction model

Numerical simulations of contrail-to-cirrus transition – Part 1: An extensive parametric study

Study of contrail microphysics in the vortex phase with a Lagrangian particle tracking model

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