Topic Number: 2 (version of 5 July 2013) Contrails and contrail impact on cirrus formation. Ulrich Schumann, Andy Heymsfield, Patrick Minnis

Transcription

1 Topic Number: 2 (version of 5 July 2013) Contrails and contrail impact on cirrus formation Ulrich Schumann, Andy Heymsfield, Patrick Minnis Klaus Gierens, Kaspar Graf, Stephan Kox, Bernhard Mayer, Andreas Minikin, Martin Schnaiter, Simon Unterstraßer, Christiane Voigt et al. dedicated to Hermann Mannstein (9 November January 2013)

2 Presentation Layout (as suggested by Darrel Baumgardner) 1. General Description of Topic Theme and Objectives of the Topic Working Group 2. Brief Status of this Topic after the July, 2010 workshop 3. What progress has been made in the last three years? 4. What are the remaining unknowns and uncertainties and how do they impact our fundamental understanding of the atmosphere, climate change, weather and society in general? 2

3 Contrail formation types aerodynamic contrail exhaust contrail Exhaust contrails Aerodynamic contrails Distrails short living contrails persistent contrails contrail cirrus soot cirrus short living and persistent contrails Persistent contrails / contrail cirrus 3 cloud holes & distrails soot cirrus???? 3

4 Theme and Objectives of the Topic Working Group what do we currently understand about ice particle properties in contrails? Contrail formation, in particular of exhaust contrails Approximate cover, ice particle concentration, habits, optical properties and radiative forcing estimates where are the gaps in our knowledge base? Nucleating and sublimation process from engine to end of wake vortex phase Crystal concentrations, sizes, shapes, composition "preactivation" and chemical aging of ice nuclei Sublimation of contrails Competition for humidity between contrails and cirrus Aggregation, sedimentation, fall streak formation Cover for given -threshold (with contrail-contrail and contrail-cirrus overlap) Aerodynamic contrails, distrails and their effects on ice clouds Life cycle and life time Aerosol (soot etc.) impact Accurate radiative forcing why do these gaps exist and how do we move forward to fill these gaps? multi-scale issue! - requires multi-sensor observations in airborne campaigns laboratory simulations, e.g. of preactivation and aging Lagrangian model and observation studies from first nucleation to globe 4

5 Brief Status of this Topic after the July 2010 workshop (see BAMS article) Reference: Baumgardner et al., IN SITU, AIRBORNE INSTRUMENTATION - Addressing and Solving Measurement Problems in Ice Clouds, Bull. AMS, 93 (2), ES29-ES34, 2012 Contrails and contrail-induced cirrus were addressed (by Philip R.A. Brown, Andy Heymsfield, and Jean-Francois Gayet). (see also Heymsfield et al., BAMS, 2010) Findings as of 2010: Key unresolved questions with respect to contrail cirrus: relative roles of homogeneous and heterogeneous nucleation, relationship between ice nuclei (IN) and ice crystal concentration,, optical properties of ice crystals as a function of habit. Instruments limitations (ice crystal shattering and sample volume) for small cloud particles (< 50 um) (basically similar to those for natural cirrus) New since then: from contrail formation to contrail life cycle 5

6 specific from 2010: Still true. In addition, stronger use of MODIS and MSG 6

7 At least 78 new publications since 2010 workshop: [Atlas and Wang, 2010; Bedka et al., 2013; Burkhardt and Kärcher, 2011; Burkhardt et al., 2010; Carleton et al., 2013; Carleton and Travis, 2013; Chen et al., 2012; De Leon et al., 2012; Demirdjian et al., 2012; Duda et al., 2013; Ewald et al., 2013; Field et al., 2012; Forster et al., 2012; Frömming et al., 2011; Frömming et al., 2012; Gayet et al., 2012; Gettelman and Chen, 2013; Gierens, 2010; Gierens, 2012; Gierens and Dilger, 2013; Gierens et al., 2011a; Gierens et al., 2011b; Graf, 2013; Graf et al., 2012; Guignery et al., 2012; Heymsfield et al., 2010; Heymsfield et al., 2011; Irvine et al., 2012; Irvine et al., 2013; Iwabuchi et al., 2012; Jacobson et al., 2011; Jeßberger et al., 2013; Jones et al., 2012; Kärcher and Burkhardt, 2012; Kärcher et al., 2010; Kox, 2012; Kübbeler et al., 2011; Laken et al., 2012; Lee et al., 2010; Lewellen, 2012; Liou et al., 2013; Mannstein et al., 2010; Mannstein et al., 2012; Markowicz and Witek, 2011a; Markowicz and Witek, 2011b; Minnis et al., 2013; Misaka et al., 2012; Naiman et al., 2011; Naiman et al., 2010; Newinger and Burkhardt, 2012; Paoli et al., 2013; Paugam et al., 2010; Ponater, 2010; Ponater et al., 2012; Rädel and Shine, 2010; Rap et al., 2010a; Rap et al., 2010b; Ryan et al., 2011; Schumann, 2012; Schumann and Graf, 2013; Schumann et al., 2011a; Schumann et al., 2012a; Schumann et al., 2013; Schumann et al., 2011b; Schumann et al., 2012b; Spangenberg et al., 2013; Unterstrasser and Gierens, 2010a; b; Unterstrasser and Sölch, 2010; Unterstrasser et al., 2012; Vázquez-Navarro et al., 2010; Vázquez-Navarro et al., 2012; Voigt et al., 2011; Voigt et al., 2010; Wong and Miake-Lye, 2010; Xie et al., 2012; Yang et al., 2010; Yi et al., 2012] for details, see separate list 7

8 What progress has been made in the last three years? General Aircraft-Induced holes Aerodynamic contrails Aviation induced cloud changes analyzed from observation and model results New BC and traffic data Modeling LES (3d turbulence resolving + 2-moments, Lagrangian, binned microphysics) Global contrail cirrus simulations Field experiments ICE-L (above -32 C, with aerodynamic contrails), 2007, US CONCERT 2008 and 2011: analysis of particle shape, aircraft effects, soot emissions, DE COntrails Spreading Into Cirrus (COSIC 2011), UK TC2 SAFIRE (contrails and climate, ongoing), F preparation of ML-CIRRUS with HALO, DE Satellite observations Linear contrail cover, microphysics, RF, life time, cirrus, OLR, RSR, tau, z top More insight in detection efficiency contrail cirrus transition (cover, tau, OLR, RSR) Aviation induced cloud changes deduced from 8 years of MSG data in NAR ground based contrail and cirrus observations, with hints for soot cirrus 8

9 Remaining unknowns and uncertainties and impact General issue: What are the effects of contrail cirrus and from aviation induced cloud changes on the atmosphere and on climate? Key science issues (containing several sub-issues; maybe, a somewhat subjective selection) What is the life time of contrails? What controls radiative forcing? Does aviation soot impact cloudiness? Many others, e.g Given the vast amount of traffic around major airports, what are the local effects of aircraft on precipitation via aerodynamic contrails? Interaction of contrails and aggregation effects in contrails 9

10 the following 30 selected slides will be explained only briefly. They serve to illustrate the progress in understanding and the open issues 10

11 Aerodynamic contrails (Gierens et al., 2009; Kärcher et al., 2009) (Gierens et al., 2011) Form by by adiabatic cooling above curved aircraft structures in atmospheres with about -43 C < T < -25 C (Gierens and Dilger, 2013) Uncertain but likely <1.E13/kg ice particles per fuel mass. Likely short lived and of small climate impact 250 hpa 300 hpa Mid-latitude Persistence probability < hpa 11

12 Distrail example, possibly in liquid water clouds photo by Bernhard Mayer (2013) ADSB data analysis (U. Schumann): Time 14:52 UTC 7 March 2013 DLH61A from Barcelona to Munich A km/h N, E sinking at about 2 km altitude asl ambient temperature around freezing level: -5 C < T < 2 C according to radiosounding Munich-Schleissheim of 12 and 24 UTC 7 March

13 Heymsfield et al. (2011) 13

14 forms by freezing of supercooled liquid clouds similar to some distrails Holes may result from ice generated by aerodynamic contrails at air temperatures above -40 C. Heymsfield et al. (2011) 14

15 Exhaust contrail formation mostly well known Form from engine exhaust H 2 O mixing with cool (and humid) air after liquid saturation (Schmidt-Appleman criterion); slightly engine dependent (Schumann, 1996) Soot and volatile aerosols influence ice formation during jet phase (Kärcher et al.,1996; Schumann et al., 2013) Contrails interact with jet dynamics, primary and secondary wakes vortices, shear. Some particle get lost by mixing and adiabatic warming in sinking wake (Greene, 1986; Unterstrasser et al., 2012). Contrails persist in ice supersaturated or lifting air masses Contrail ice particles grow by mixing with ambient air and uptake of ambient humidity G= e e / T e G ( M H 2 O c / M air ) Q liquid saturation p pei (1 ) ice saturation 1: short-lived, 2: persistent, 3: threshold, 4: no contrail. H 2 O fuel 15

16 Contrail and plume dynamics in aircraft wakes ~50 m t = 0 s. t ~ 10 s. Crow instability O Z w t ~ 100 s. Jet regime Z w = u a/c t u a/c = 250 m/s (cruise) Vortex roll-up; jet/vortex interaction Vortex regime t ~ 1000 s. a few hours Dissipation regime Vortex descent; Crow(elliptic) instability Wake evolution in four wake regimes (Gerz et al., 1998). Slide from Roberto Paoli, CERFACS Stratification; vortex break-up Diffusion regime Atmospheric variability... to global scales ~ 1 km 16

17 Vortex bursting and tracer transport of a counterrotating vortex pair Misaka, Holzäpfel et al., Phys. Fluids (2012) 17

18 Ice number densities in the vortex phase Relative particle concentrations in contrails RHI 120% 1 min 3 min 5 min 5min, RHI 110% Formation of vortices on the wing tips In-mixing of the emissions Downward transport and dilution ice crystal sublimation Unterstrasser, Sölch and Gierens (Atmospheric Physics, 2012) 18

19 Fraction of ice particles surviving the wake vortex phase important for contrail climate impact Importance based on global contrail simulation with CoCiP (Schumann et al., GRL, 2013): Increase of ice particle number at end of wake vortex phase by factor of 2 implies full curve: Bulk microphysics module (BM) with lognormal size distribution dashed: Lagrangian particle tracking microphysics module (LCM) Unterstraßer and Sölch (ACP, 2010) increases of: by a factor net RF: 1.64 tau: 1.27 cover: 1.29 age: 1.16 width: 1.22 open: Ice particle formation from engine exhaust until jet mixing with primary and secondary wakes 19

20 How do multiple contrails and contrails and cirrus interact and compete for ambient humidity? 4 h of animation, color: extinction - time/min: (Unterstrasser, TAC, 2012) 20

21 High (ice concentration size) in contrails consumes ambient supersaturation and hence reduces further cirrus formation Here N*r 1000 m cm -3, -> approach of saturation within < 10 s How does supersaturation in contrails change in diluted contrail and for quick vertical lifting? Air outside of contrails ice super or sub- saturated RHI in contrails relaxes near 100% RHI sensitive to temperature accuracy Kaufmann, Voigt, Schäuble, (TAC, 2013) Korolev and Mazin (2003) 21

22 Contrail ice particle size distribution and microphysical processes 1000 Sublimation Dilution Growth 100 Contrail dn/dlogd (cm -3 ) Deposition/ Aggregation 10 1 Cirrus Sedimentation d (µm) Schröder et al., JAS, 2000 (Voigt et al., GRL (2011) How sensitive are these results to the old FSSP-300 used? 22

23 Shattering effects likely small for small contrail ice particles Extinction coefficients from FSSP-300 and Polar Nephelometer (PN) measurements. FSSP-300 with different size calibrations: Polar Nephelometer Extinction (km -1 ) a FSSP-300 Extinction (km -1 ) FSSP-300 Extinction (km -1 ) b young plume with PN and FSSP mounted on opposite wings: separately in and out of contrail (a) for spherical particles (red data) (b) for spherical (red)/aspherical (blue data) FSSP size calibration depending on PN-derived asymmetry parameter g. Red: g > 0.85; blue: g < Gayet et al. (2012) 23

24 (Schumann et al., JAS 2010)

25 Exhaust dilution and contrail ice particles in aircraft wakes: higher ice number concentration than expected Schumann, Jeßberger, Voigt (GRL, 2013) If ice nucleated on soot, than at least /kg of soot particles per burnt fuel mass. Ice particle sublimate in sinking and adiabatically heating wake vortex. Note: 3 more aviation BC than expected so far (Stettler et al., 2013, subm.) 25

26 Impact of aircraft type on total contrail extinction EA 140 Observations (FSSP-300) and linear fit total extinction, EA (m) Observations (PN) Febre et al. (2009) Sussmann and Gierens (1999) A340 A319 A fuel consumption m F (kg/km) Jeßberger, Voigt, Schumann et al., ACPD, 2013 Total extinction EA = da B (Unterstrasser and Gierens, part I, 2010) with A contrail cross section, B width, extinction, optical depth EA depends linearly on fuel consumption per flight distance as a consequence, contrail climate impact depends on aircraft properties 26

27 AWACS example: Contrails initiate cirrus formation in air masses without other clouds - how often is this the case? (Schumann, 2002) 27 27

28 Possibly more often: Contrails form inside and co-exist with thin cirrus in ice-supersaturated air masses (Immler et al., 2008) 28

29 In humid air, contrails particle grow by deposition and possibly aggregation, sediment and end in fallstreaks (Miloshevich and Heymsfield, JAOT, 1997) 29

30 altitude in km ( km) Lidar: Contrails spread by wind shear and end in fall streaks (Freudenthaler, PhD thesis, Munich, 2000) altitude in km ( km) backscatter signal from Lidar on Falcon (Schumann, Ann. Geophys., 1994, based on observations by M. E. Reinhardt) distance in km ( km) distance in km (0-40 km) 30 (Atlas et al., 2006)

31 Contrails occurrence observed with CALIPSO and MODIS and simulated with CoCiP, based on ECMWF and ACCRI traffic Observed (Iwabuchi et al., 2012) Simulated (Schumann, 2012, ) 31

32 Optical depth pdf derived vom CALIPSO and models Iwabuchi et al.(2012) Frequency TAUW Solar optical thickness Voigt et al. (2011) Immler et al. (2008) Kärcher and Burkhardt (2012) 32

33 Contrail cover from MODIS (Duda et al., 2013, ACCRI BAMS paper tbs; NASA Langley, using Mask B, traffic filtered, fractional cover in %, 2006). Issues: large cover over North Atlantic, low cover over Europe/USA, CDA mask sensitivity, traffic filtering CDA detection efficiency depends on - land/ocean contrast, - contrail-cirrus overlap, - satellite overpass times relative to traffic diurnal cycle 33

34 Computed contrail cover (with CoCiP, based on ACCRI traffic and ECMWF meteorology) There are far more (overlapping) contrails than detected from satellites (Schumann and Graf, 2013) 34

35 By far not all linear contrails are detectable by contrail detection algorithms Of the contrails observed with the all-sky camera of 1 5 km width 60 65% are visually detectable in AVHRR data while only 17% are identified by an automated contrail detection algorithm (CDA). (Mannstein et al., 2011) 35

36 From MODIS data: Microphysics of contrail cirrus compared to linear contrails Minnis et al. (GRL 2013) The mean optical depths and effective particle sizes of the contrail cirrus were 2 3 times and 20% greater, respectively, than the corresponding values retrieved for the adjacent linear contrails. When contrails form below, in, or above existing cirrus clouds, the column cloud optical depth is increased and particle size is decreased. 36

37 Contrail properties from 2006 Aqua MODIS retrievals. (a) Contrail average particle size vs. contrail temperature for day (solid line) and night (dashed line). (b) Average contrail optical depth vs. contrail temperature. (c) Number of contrail pixels in each temperature bin. Bars show one standard deviation about the mean. (Bedka et al., 2013; NASA Langley). 37

38 Net contrail radiative forcing from MODIS and a model during JAJO 2006 from Aqua MODIS data (Spangeberg et al., 2013; NASA Langley). ----> far smaller than computed with CoCiP, see below CoCiP, Schumann and Graf (2012) 38

39 Remaining unknowns and uncertainties and impact obviously much progress but many details remain unknown or uncertain General issue: What are the atmospheric and climate effects of contrail cirrus and from aviation induced cloud changes? Key science issues (containing several sub-issues) What is the contrail cover for the fleet, life time of single contrails? What controls radiative forcing? Does aviation soot impact contrails, cloudiness, hydrological cycle? 39

40 Science questions, part 1: Life time of contrails cirrus How can we understand - relative humidity inside and outside of contrails - particle losses in young and aged contrails - spreading of individual contrails - Interaction of neighbouring contrails (competition for humidity) - formation of contrail outbreaks - ice particle aggregation, sedimentation and fall streaks - dryout by subsidence and mixing with dry air - contrail - cirrus - interactions - impact of mean and fluctuation vertical motions - others? 40

41 What determines the life time (or cover) of contrails Importance: Cover and RF scale approximately with the square of age, because area per flight length = age width(t) dt RHi>1 RHi=1 depth Number of ice particles in young contrail determined mainly by emissions and wake dynamics number of soot particles ambient RHi, p, Temperature and particle losses in sinking wake vortex V T =f(r) Contrail life time depends on initial number of ice particles ambient RHi, T, p mixing with ambient air sedimentation ambient vertical motion incl. waves interaction with ambient cirrus and other contrails radiative heating 41

42 Contrail cirrus may persist for, e.g., 18 hours (Haywood et al., JGR, 2009) 42

43 Animation shows: Contrails can be tracked in Meteosat Scenes 43 An automatic contrail tracking algorithm, M. Vazquez-Navarro, B. Mayer, H. Mannstein, Atmos. Meas. Tech. (2010) 43

44 Life time of ISSR and contrails: mean < 1 h derived from MSG-observed (i.e., thick) contrails (Vazquez-Navarro; Mannstein et al., 2012) Model results, depend strongly on particle loss processes in the model: aggregation, sedimentation, turbulent sublimation (Schumann, 2012) 44

45 The diurnal traffic cycle in the North Atlantic: a fingerprint for aviation induced cirrus Annual mean Air traffic density (ATD) in km/(km 2 h) NAR EUR-M MSG-Visibility Vertically integrated traffic data above 6 km from EUROCONTROL at 15 min time resolution (Graf et al., GRL, 2012) 45

46 Cirrus cover and top of the atmosphere radiances determined from Meteosat SEVIRI (day and night time) uses 7 IR channels of SEVIRI cirrus detection at day and night. combines morphological and multispectral threshold tests detects optically thin ( > 0.2) ice clouds. Data include 8 years of 15 min cirrus cover, Feb 2004 Jan 2012 Retrieval of integrated longwave and shortwave top-of-atmosphere irradiances from MSG/SEVIRI (RRUMS) (Vazquez- Navarro et al., AMT, 2012) (Krebs, Mannstein, Bugliaro, Mayer, 2007; Ewald et al., 2012; Vazquez-Navarro et al., 2012, Graf et al., 2012, Graf, PhD 2013; Kox, PhD, 2012) See also COCS (Kox, 2012) 46

47 Life time of contrail cirrus reflected in cirrus response to air traffic double wave over North Atlantic; see animation: can this analysis be supported by in-situ data? what explains the remaining differences? weather dynamics? contrail-humidity interaction? soot effects? model physics? Graf et al. (GRL; 2012); Schumann and Graf (JGR, 2013) 47

48 Besides cirrus cover, also the optical depth diurnal cycle can be derived from Meteosat SEVIRI using neural network trained with CALIPSO observations (Kox, Ph.D thesis 2012) Further results show diurnal cycle in cover and optical depth in correlation with air traffic. See also Graf et al. (2012) 48

49 Science questions, part 2: Soot cirrus - how much of the soot contributes to ice nucleation in contrails (up to 100%?) and cirrus (0.1-10%?) - do soot particles or soot aggregates from sublimating contrails or cirrus particles contain ice remainders (Edwards et al., 1970) - does this processed (wet) soot cause renucleation of ice particles > laboratory investigation required! - how gets soot processed chemically in contrails and cirrus? - what is the soot life time globally? (models compute weeks to months) - what are the differences in cirrus/soot properties before and after passage of major air traffic density? - can aviation-soot -cirrus be observed? Soot concentration (grey) and number N CVI of ice crystals > 5 m (line) soot aggregation? (Ström and Ohlson, JGR, 1998) 49

50 Examples of ice particles measured with HOLIMO II (HOLographic Imager for Microscopic Objects II) in mixed phase clouds at Jungfraujoch Are these soot aggregates? Do such soot aggregates occur in cirrus particles? Henneberger, Fugal, Stetzer, Lohmann, HOLIMO II (ATMD, 2013)

51 Science questions, part 3: Radiation and climate impact - is it possible to setup a data set to constrain radiative fluxes? from -insitu - airborne remote sensing - space (SEVIRI, CALIPSO, MODIS, METOP, etc.) - ground (e.g. Lidar, Radar, balloons, radiometers, webcam, supersites) - weather analysis - models- Climate impact: why is the global warming effect from contrail RF less than for CO 2? (efficacy of contrail RF 0.3 to 0.6), see Ponater (2010); Rap et al. (2010); Ponater et al. (2005, 2006, 2012), Hansen et al., (2005) 51

52 Global contrail radiative forcing in mw m 2. Wide range of net and absolute SW /LW ratio values Optical depth s at 550 nm given when fixed Column d.c. : diurnal traffic cycle included. LW: longwave SW: shortwave net: LW+SW (Schumann and Graf, 2013) Spangenberg et al. (2013) obs, yes 17.9, -7.3, 10.6, 0.41 LW warms, SW cools; hence: Net effect (LW+SW) decreases when the SW /LW ratio increases 52

53 Total radiative forcing by contrail cirrus is far larger than from linear contrails (from ECHAM GCM) net RF young contrails net RF contrail cirrus Burkhardt and Kärcher (Nature Clim. Change, 2011) 53

54 Radiative forcing from contrail cirrus: SW/LW ratio? RF/(mW/m 2 ) RF ECHAM4 CoCiP -CCMOD 0 LW SW Ci Net LW SW Net mw/m 2 mw/m 2 Burkhardt and Kärcher (2011) Schumann and Graf (2013) 54

55 Longwave (LW)/ shortwave (SW) RF depends on: contrail properties (, r eff, habit, T) and (!!!) on solar and terrestrial parameters (RSR, SDR, OLR, ambient cirrus) also on 3d cloud structures and cloud heterogeneity RSR= reflected shortwave radiation SDR= solar direct radiation OLR= outgoing longwave radiation (Schumann et al., 2012) 55

56 Models compute number and volume of ice -> r vol Optical depth depends on volume and cross-section -> r eff =? depends on shape of size distribution and habit Schumann et al. (JAS, 2011) 56

57 What determines radiative forcing (RF) from contrails? based on optical microphysics from Key et al. (2002) and Yang et al. (2005) and libradtran (Mayer and Kylling, 2005), Schumann et al. (JAMS, 2012) among others:, r eff, shape, Temperature, soot content solar / terrestrial parameters are also very important 57

58 Shape of ice particles in young contrails A380 Fraction of quasi spherical particles decreases with contrail age A380 Gayet, Shcherbakov, Voigt et al. (ACP, 2012) Large fraction of aspherical particles (low g) already in rather young contrails, aspherical fraction increasing with age Open: particle details (shape, roughness, aerosol mixing state, soot absorption,, size distribution, dependence on T and RHi, w, contrail age, ambient cirrus etc.) 58

59 Conclusions what do we currently understand about ice particle properties in contrails? Contrail formation Approximate cover, ice particle concentration, habits, optical propertied and radiative forcing estimates where are the gaps in our knowledge base? Nucleating and sublimation process from engine to end of wake vortex phase Crystal concentrations, sizes, shapes, composition "preactivation" and chemical aging of ice nuclei Sublimation of contrails Competition for humidity between contrails and cirrus Aggregation, sedimentation, fall streak formation Cover for given -threshold (with contrail-contrail and contrail-cirrus overlap) Aerodynamic contrails, distrails and their effects on ice clouds Life cycle and life time Aerosol (soot etc.) impact Accurate radiative forcing why do these gaps exist and how do we move forward to fill these gaps? multi-scale issue! - requires multi-sensor observations in airborne campaigns laboratory simulations, e.g. of preactivation and aging Lagrangian model and observation studies from first nucleation to globe 59