3D-simulations of the wake vortex evolution What properties contrail modelers need to know? Simon Unterstraßer

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1 3D-simulations of the wake vortex evolution What properties contrail modelers need to know? Simon Unterstraßer Folie 1

2 Contrail modeling during the vortex phase Dynamical and microphysical processes are significant for the contrail evolution during the vortex phase The interaction of a wake vortex and a contrail changes the contrail s structure and microphysics (timescale of minutes). This has an impact on the properties of the evolving contrail and its transition into a cirrus (timescale of hours). How do dynamical details (esp. during the vortex phase) affect the contrail evolution? Where are thematic intersections with pure wake vortex modeling? Folie 2

3 Overview of microphysical processes Now: Relevant in the vortex phase Nucleation Depositional Growth Sublimation Formation of ice crystals relative humidity >100% Microphysical Processes relative humidity <100% Collision + Sticking Sun Earth Sedimentation Aggregation Radiation Folie 3

4 Contrail modeling during the vortex phase Three major features of the contrail evolution during the vortex phase: vertical expansion spatial heterogeneity in ice distribution ice crystal loss. Folie 4

5 Vertical expansion Height H of contrail and vertical wind shear determine the spreading rate of the evolving contrail. Folie 5

6 Spatial Heterogeneity in ice distribution Induces differential heating of the surrounding air via radiation processes and latent heat release. These diabetic processes trigger turbulence in the later stages of the contrail evolution Age: 2.5 hours, Width: 20km Folie 6

7 Ice crystal loss (1/2) Reduces the number of ice crystals N in the evolving contrail-cirrus. N affects the optical depth and the lifetime of contrails (via sedimentation) Folie 7

8 Ice crystal loss (2/2) Primary wake: Adiabatic compression in the downward moving vortex pair increases the saturation pressure. Reduction of relative humidity results in crystal mass sublimation and eventually in crystal number loss in the primary wake. Secondary wake: Crystals that are not entrained into the vortex during the jet phase and crystals detrained from the vortex system during the vortex phase. Take up vapour from moist ambient air. The extent of crystal loss depends on the vertical displacement of the vortex pair. Different microphysical evolution in the primary and secondary wake. Folie 8

9 Temporal Evolution (T = 217K, RH i = 105%) Folie 9

10 Temporal Evolution (T = 217K, RH i = 105%) Folie 10

11 Temporal Evolution (T = 217K, RH i = 105%) Folie 11

12 Temporal Evolution (T = 217K, RH i = 105%) Folie 12

13 Temporal Evolution (T = 217K, RH i = 105%) Folie 13

14 Temporal Evolution (T = 217K, RH i = 105%) Folie 14

15 Temporal Evolution (T = 217K, RH i = 105%) Folie 15

16 Temporal Evolution (T = 217K, RH i = 105%) Folie 16

17 Recent research on contrail vortex phase evolution Huebsch & Lewellen: 3D-code, dynamics and microphysics well-resolved, limited number of simulations Paoli, Paugam, Cariolle : 3D-code, dynamics well-resolved, limited number of simulations Unterstraßer, Sölch, Gierens: 2D-code with adjusted vortex decay, emphasis on microphysics, extensive parameter studies were carried out Folie 17

18 Recent research on contrail vortex phase evolution Unterstraßer, Sölch, Gierens: 2D-code with adjusted vortex decay, emphasis on microphysics, extensive parameter studies were carried out Folie 18

19 Microphysical evolution during the vortex phase, especially crystal loss Fraction of surviving ice crystals f n Relative humidity Rh i, in % Unterstraßer & Sölch, ACPD 2010 Folie 19

20 Microphysical evolution during the vortex phase, especially crystal loss Relative humidity RH i Temperature T Aircraft type: Γ 0, b 0, water vapor emission, EI soot Stability N BV Number of surviving ice crystals f n Eddy dissipation rate ε Initial ice crystal size distribution Engine/wing configuration Folie 20

21 Coupling/feedbacks of dynamics and microphysics Ice crystals in the primary wake can be lost, the ones in the secondary wake are safe. The longer the vortices descend, the more ice crystals sublimate. Consequences: The lifetime and descent speed must be met accurately in order to have a realistic vertical displacement. 2D-results similar to 3D-results. Detrainment rate: How many crystals can escape from the primary wake. Comparison of different models necessary. Entrainment rate: How much moist air is entrained to counteract the relative humidity decrease in the primary wake? Slows down sublimation Folie 21

22 Coupling/feedbacks of dynamics and microphysics Consequences (cont d): Initial configuration: Are all ice crystals inside the vortex system? How do these issues depend on the various aircraft type? Better representation of the variation along flight direction. Significant? Cannot be answered without 3D-simulations of contrail-to cirrus transition. Vortex rings What is (probably) not relevant? The strength of the smallest-scale eddies. too fast for a feedback to microphysics Evaluation of rolling moments Folie 22

23 Setup of a 3D contrail model Collaboration with I. Sölch, I. Hennemann, T. Misaka EULAG is 3D-code Use 256x400x512 (spanwise, flight direction, vertical) = 52e6 grid points Include initial turbulent fluctuations and analytical vortex definition Microphysical approach: Lagrangian treatment of individual ice crystals. Each ice crystal stores its microphysical properties and subgrid-position. Much more precise than bulk microphysical models. Critical issues: memory-consuming, load-imbalancing, large amount of data One typical simulation runs >10e4 CPUh, 50Gb memory/core Folie 23

24 First results A319 in a calm, neutral atmosphere Evaluation of vortex cores with a newly developed tracking algorithm (I. Hennemann, PhD 2009) Folie 24

25 Conclusions During the vortex phase the contrail evolution is affected both by dynamical and microphysical processes Microphysical evolution different in primary wake (sublimation) and secondary wake (growth) Microphysical variability, partly irreducible uncertainties Dynamic issues relevant to contrail microphysics: descent speed and final vertical displacement detrainment of ice particles entrainment of ambient air initial distribution of exhaust material (incl. ice crystals) Dependence on aircraft type Folie 25

26 Acknowledgement Thanks to WakeNet3 for the opportunity to give a talk at this workshop! Folie 26

More and different clouds from transport

More and different clouds from transport Klaus Gierens Deutsches Zentrum für Luft- und Raumfahrt (DLR) Institut für Physik der Atmosphäre Oberpfaffenhofen, Germany Transport Emissions: The Climate Challenge