from contrail formation to contrail-cirrus a modeling ... · pdf filefrom contrail formation...

www.DLR.de • Chart 1 S. Unterstrasser

From contrail formation to contrail-cirrusA modeling perspectiveSimon Unterstraßer

www.DLR.de • Chart 2

Motivation – Temporal evolution of a Contrail (1/4)

The contrail evolution can be divided into 3 temporal phases:

Vortex DispersionJetPhase

pPhase

2 - 4

Phase

5 - 10s minutes Minutes to hours


Motivation – Temporal evolution of a Contrail:Jet Phase (2/4)

Vortex DispersionJetPhase

pPhasePhase


Motivation – Temporal evolution of a Contrail: Vortex Phase (3/4)

DispersionJet Vortex

V t h (2 4 i )

pPhasePhase Phase

Vortex phase (2 - 4min): Main feature is the descent of the vortex pair (200m-600m)→ crystal loss due to adiabatic warming


Motivation – Temporal evolution of a Contrail: Dispersion Phase (4/4)

Jet Vortex Dispersion

Di i h ( i t t

Phase Phasep

Phase

Dispersion phase (minutes to hours): spreading of contrails by turbulent mixing and vertical wind shear

Atmospheric conditions

Sedimentation and radiation become important


Jet phase

Important questions:

How many ice particles form?

How much exhaust is entrained into the wake vortex?


Jet phase

How many ice particles form?

Boxmodel simulation withBoxmodel simulation withdetailed microphysicsKärcher & Yu, GRL, 2009

Depends on EI_soot andtemperature

Soot-poor regime: Ambientliquid particles serve as icenuclei


Jet phase

How much exhaust is entrained intothe wake vortex?

LES with compressible code NTMIX.Paoli et al, PhyFluids, 2013

Detailed 3D-simulation of jet/vortexinteractionSimplified ice activationSimplified ice activation


2-Engine 4-EngineJet phase

g g

How much exhaust is entrained intothe wake vortex?

Results for 2-Engine and 4-Engine aircraft

Initialization for vortex phasesimulations

Paoli et al, PhyFluids, 2013


Vortex phase

Important questions:

How many ice particles survive?- affects later crystal size -> optical properties,

di t ti t il di l ti lif l

What are the contrail dimensions, esp. contrail depth, after vortex break-up?

sedimentation, contrail dissolution, life cycle

shear induced contrail spreading > deeper is- shear induced contrail spreading -> deeper iseventually broader


Vortex phase

Simulation of wake vortex evolution (descent and break-up) and contrail icemicrophysicsEULAG LCM: 3D LES with Lagrangian ice microphysicsEULAG-LCM: 3D-LES with Lagrangian ice microphysics

3D simulation with 80e6 grid pointsand 160e6 SIPs

covers first 5 minutes behind aircraftcovers first 5 minutes behind aircraft

Vortex phaseContrail depth and ice crystal loss

Relative humidity RHi Temperature TAircraft type: Γ0, b0,

water vapor emissionwater vapor emission, EIsoot

C il d hThermal stratification NBV

Ambient turbulence intensity EDR ε

1. Contrail depth

2. Number of surviving ice crystals fn

Initial ice crystal size

ice crystals fn

distribution

Number of ice crystals

Vertical wind shear


Vortex phase – Dimension of Exhaust PlumeVariation of parameters that affect wake vortex properties and evolution:Variation of parameters that affect wake vortex properties and evolution:Stratification, Turbulence, Vertical wind shear, Aircraft mass

T i d d t LES d lTwo independent LES modelsEULAG-LCM (solid), NTMIX (dotted)

Strong stratification, weak turbulence

Stronger turbulence

Weaker stratification

Unterstrasser et al., ACP, 2014


Vortex phase – Dimension of Exhaust PlumeVariation of parameters that affect wake vortex properties and evolution:Variation of parameters that affect wake vortex properties and evolution:Stratification, Turbulence, Vertical wind shear, Aircraft mass

Plume dimensionsfor type B777/A340 aircraftafter vortex break-up (t = 5min)p ( )

Weak stratification

Unterstrasser et al., ACP, 2014


Vortex phase – Contrail depthSensitivity to relative humidity RHiSensitivity to relative humidity RHi

Vertical profiles of ice mass

Contrails are deeper compared to previous 2D-simulation results (Unterstrasser et al, MZ, 2008, Unterstrasser & Sölch, ACP, 2010), , )

Unterstrasser, in review JGR


Vortex phase – Ice crystal lossSensitivity to relative humidity Rhi and temperatureSensitivity to relative humidity Rhi and temperature

F ti f i i i t lFraction of surviving ice crystals

Survival rates of previous 2D-estimates (Unterstrasser & (Sölch, ACP, 2010) areconfirmed

Unterstrasser, in review JGR


Vortex phase – Ice crystal lossSensitivity to number of initially formed ice crystalsSensitivity to number of initially formed ice crystals

crys

tals

xph

ase

onof

ice

c

fter v

orte

x

Frac

tio

Before vortex phaseA

f

Unterstrasser, in review JGRUnterstrasser, in review JGR


Vortex phaseResults so far for type B777/A340 aircraftResults so far for type B777/A340 aircraft

Extension to various aircraft types: see talk by N. Görsch


Dispersion phase – Contrail to cirrus transition

Evolution depends on a multitude ofEvolution depends on a multitude of parameters:

relative humidity wind shear temperature radiation depth of supersaturated layerdepth of supersaturated layer contrail properties after vortex

phase interaction with natural cirrus interaction with other contrails

Partly answered in Unterstrasser & Gierens, ACP, 2010a & b, Jensen et al, JGR,1998


Dispersion Phase – Contrail to cirrus transition- EULAG-LCM can serve as benchmark model for simplied model CoCiPEULAG LCM can serve as benchmark model for simplied model CoCiP- Both models simulate individual contrails- Compare models for a multitude of atmospheric scenarios

EULAG-LCM CoCiP

Model purpose:p pEULAG-LCM: high resolution simulations for selected cases with detailed dynamics and ice microphysicsCoCiP: coarser simulations for global scale applications

Validation along model chain: EULAG-LCM -> CoCip -> GCM

Individual contrailsLarge scaleLarge scale


Dispersion phase – Contrail cluster formation

Evolution of eight contrails in a supersaturated layer with background vertical wind shear over 4 hours.


Dispersion phase – Contrail cluster formation

Formation of contrail cluster: Saturation effects in regions

color: shear s=red 0.002 s-1 Saturation effects in regions

with dense air traffic

Non-linear scaling of contrail

green 0.004 s-1

blue 0.006 s-1

linestyle: wsyn=solid 1 cm/s climate with air traffic densitysolid 1 cm/sdotted 2 cm/sdashed 20 cm/s


The end.

Thanks to K. Graf and U. Schumann for CoCipcomparison runs

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