More and different clouds from transport

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1 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 Results from IP QUANTIFY and SSA ATTICA Brussels, 24 June 2010

Atmosphäre Oberpfaffenhofen, Germany Transport Emissions: The

2 Acknowledgements Veronika Eyring and the ATTICA ships team David Lee and the ATTICA aviation team Kaspar Graf, Hermann Mannstein, Ulrich Schumann Christos Zerefos, Kostas Eleftheratos Mathias Schreier, Andy Sayer, Don Grainger 2

Hermann Mannstein, Ulrich Schumann Christos Zerefos,

3 Contents Climate Clouds How can clouds be altered? Contrail formation Aerodynamic contrail formation Formation of ship tracks Manifestations of cloud changes induced by traffic emissions 3

4 Climate: Dynamical equilibrium between energy inflow and outflow Trenberth et al., 2009: Earth s Annual Global Mean Energy Budget 4

5 Clouds visible light IR window water vapour Eumetsat image gallery Clouds interact strongly with both solar and terrestrial radiation, as evidenced by their clear visibility on such satellite images (contrast). Systematic cloud changes therefore impact the radiative equilibrium. 5

evidenced by their clear visibility on such satellite images

6 Climate warming and cooling by clouds Cirrus clouds both cool and heat the atmosphere, and the total can be positive or negative. Uncertainties arise from subtracting large positive and negative values. trapping: heating colours inverted! reflection: cooling 6

7 Detection of cloud changes is difficult... no two clouds are equal. Therefore to detect systematic cloud changes is a question of statistics with interpretation aid from theoretical cloud physics. As it is statistics, it implies uncertainties. 7

8 ... unless they appear as contrails and ship tracks Contrails and ship tracks are easily detectable due to their particular line shape. Even automatic detection and tracking methods work. 8

9 How can clouds be altered? Ingredients for cloud formation: high relative humidity (saturation and supersaturation) appropriate aerosol particles which act as condensation and ice nuclei. Particles are present in the natural atmosphere in copious numbers. Anthropogenic particle emissions change composition (chemical composition, surface structure) and number concentration of the aerosol. Cloud formation where no natural cloud would form (contrails, some ship tracks) Modification of natural cloud formation processes clouds with different microphysical and optical properties 9

and ice nuclei. Particles are present in the natural atmosphere in copious numbers.

10 Contrail formation Contrail formation is like breathing in cold air: Mixing of hot and moist exhaust gases with sufficiently cold ambient air can lead to transient water (super)saturation condensation on exhaust and entrained ambient particles freezing contrail Contrails can persist for hours in ice-supersaturated airmasses. 10

water (super)saturation condensation on exhaust and entrained ambient particles

11 Aerodynamic contrail formation Pressure drop around wings leads to strong cooling of the air leads to very high values of supersaturation for some milliseconds leads to condensation and freezing on aerosol particles in the air flow 27 June 2006, 1406 UTC, Norderney, Germany Phenomenon is rarely observable under cruise flight conditions Dieter Klatt, D-Oldenburg 11

condensation and freezing on aerosol particles in the air flow 27 June 2006, 1406 UTC,

12 Formation of ship tracks: natural aerosol Normal conditions over the sea: small numbers of sea salt and sulphate aerosol Illustration courtesy of M. Schreier, Univ. Bremen 12

13 Formation of ship tracks: cloud formation small number of condensation nuclei to form droplets small number of big cloud droplets 13

14 Formation of ship tracks: Twomey effect addition of aerosol particles from ship exhaust more condensation nuclei large number of small cloud droplets higher reflectivity Twomey effect 14

15 Manifestations of cloud changes induced by air traffic Graf et al.,

16 Large scale aviation impact on cirrus clouds: Optical and microphysical properties Aviation influence is expected to decrease ice crystal numbers in clouds formed in clean environments increase ice crystal numbers in clouds formed in polluted environments Either cooling or warming can result, depending on predominating conditions. Only two numerical studies so far with inconclusive results Liu, Penner, Wang 2009 Penner, Chen, Wang, Liu, 2009 W/m² 16

formed in polluted environments Either cooling or warming can result, depending on predominating conditions.

17 Large scale aviation impact on cirrus clouds: Coverage changes (trend analyses) Europe HIGH air traffic corridors LOW air traffic corridors Cirrus trends (% per decade) N. America, Europe, N. Atlantic, N. Pacific HIGH air traffic corridors LOW air traffic corridors Anomalies (%) Differences (%) (+0.6) (-0.3) (+0.9) Anomalies (%) Anomalies (%) Differences (%) (+0.6) (-0.3) (+0.9) Anomalies (%) Zerefos & Eleftheratos, recent results: In all cases the differences have a positive trend which could be considered in favour of a pattern that is imposed by increasing of miles travelled by aviation in the past 20 years 17

9) 4 0-4 Anomalies (%) Anomalies (%) Differences (%) 4 0-4 4 0-4 (+0.6) (-0.3) (+0.

18 Manifestations of cloud changes induced by ship traffic Ship tracks (observations) selective phenomenon smaller droplets (incr. reflectivity) reduced drizzle formation increased lifetime 300 km long, 10 km wide Rosenfeld et al Sayer and Grainger, 2010 Behrends et al.,

reflectivity) reduced drizzle formation increased lifetime 300 km

19 Larger scale ship effects on clouds Results from numerical modelling: Regions with a frequent high amount of low clouds above the ocean are susceptible to effects from ship emissions. Ship emissions cause 5-30% increased droplet concentration increased reflectivity, causes strong overall cooling effect, very uncertain (2005 RF range: to W m 2 ) small IR effect, because affected clouds are close to surface ship tracks RF much smaller than RF due to large scale effects 9mW/m² Lauer et al. 2007, Sayer and Grainger

Ship emissions cause 5-30% increased droplet concentration increased reflectivity, causes strong overall cooling effect, very

20 Summary Traffic particulate emissions modify the atmosphere s aerosol content and aerosol properties (chemistry, surface structures) Consequences visible to everybody are contrails and ship tracks. Linear contrails warm and ship tracks cool climate (RF about a few mw/m²). Wider reaching effects from aviation are contrail cirrus (warming: a few 10 mw/m²) and indirect cloud effects on cirrus from aircraft soot (soot cirrus: size and sign of the effect currently uncertain). Wider reaching effects from ships are indirect cloud effects on low level clouds (increased reflectivity) which potentially cause strong cooling. Although we think to know the working principles, many process details are still unknown or uncertain. The quantification of the effects through measurement and modelling is quite difficult and very many measurements are needed: still large uncertainties. 20

Wider reaching effects from aviation are contrail cirrus (warming: a few 10 mw/m²) and indirect cloud effects on cirrus from aircraft soot (soot cirrus: size and sign of the effect currently

How To Understand The Climate Impact Of Aviation

How To Understand The Climate Impact Of Aviation Aviation Climate Impact: Scientific Status Ulrich Schumann, DLR Institut für Physik der Atmosphäre Understanding of Aviation climate impact - History 1971/72: Johnston, Crutzen: NO x from super-sonic transport