Ringvorlesung Planeten und Leben im Überblick. Oberflächen.. Wasser.. Atmosphären: Dynamik Atmosphären: Chemie Atmosphären: Klimaentwicklung Inneres..

Transkript

1 Ringvorlesung Planeten und Leben im Überblick Oberflächen.. Wasser.. Atmosphären: Dynamik Atmosphären: Chemie Atmosphären: Klimaentwicklung Inneres..

2 Atmosphären: Dynamik Dynamik und Transportprozesse in Planetenatmosphären Prof. Dr. Ulrike Langematz Dr. Lee Grenfell Zentrum für Astronomie und Astrophysik, Technische Universität Berlin

3 Dynamical aspects of the Earth s atmosphere

4 Bild kann nicht angezeigt werden. Dieser Computer verfügt möglicherweise über zu wenig Arbeitsspeicher, um das Bild zu öffnen, oder das Bild ist beschädigt. Starten Sie den Computer neu, und öffnen Sie dann erneut die Datei. Wenn weiterhin das rote x angezeigt wird, müssen Sie das Bild möglicherweise löschen und dann erneut einfügen. Dynamical aspects of the Earth s atmosphere 1. The sun as energy source Differential solar heating Temperature gradients Dynamics Factors affecting dynamics: Orbital parameters 11-year Schwabe-Zyklus Rotation of planet Variability of energy input Maunder Minimum 01% Hoyt und Schatten, 1993, updated

5 Dynamical aspects of the Earth s atmosphere 2. Chemical composition of Earth s atmosphere Substance Fraction [V%] Nitrogen (N 2 ) 78,08 Oxygen (O 2 ) 20,95 Argon (Ar) 0,93 Carbondioxid (CO 2 ) 0,033 Neon (Ne) (+ Noble gases) 90% dry 10% January, ppmv moist Factors affecting dynamics: chemical composition

6 Dynamical aspects of the Earth s atmosphere Short wave solar heating rate due to absorption by ozone and molecular oxygen in K/day January Temperature in C K W W K K

7 Dynamical aspects of the Earth s atmosphere 1. Radiative equilibrium in the stratosphere in summer. Zonal gemittelte Temperatur 2. zonally symmetric irradiance 2-d approximation valid 1. Dynamical disturbances in the winter stratosphere and in the mesosphere 2. longitudinal dependence 3-d dynamics summer winter Theoretical concept of zonal mean background state with imposed dynamical effects by wavelike disturbances

8 Dynamical aspects of the Earth s atmosphere Temperature and zonal wind January, zonal means SPARC climatology ( E W How does the corresponding zonal wind field look like? Polar night jet With the assumption of geostrophic balance: E W Equilibrium between Coriolis force (due to Earth rotation) and pressure E gradient force in the large scale): Geostrophic wind: u = 1/(ρf) δp/ δy Thermal W wind: W δu/δz = ~ δt/δy

9 Dynamical aspects of the Earth s atmosphere Stratospheric mean circulation Geopotential height, long-term mean, northern hemisphere winter summer H T H

10 Dynamical aspects of the Earth s atmosphere Episodic occurrences of Major Stratospheric Warmings

11 Arctic high in summer Stratospheric warming im Januar d-approximation valid u ( λ, ϕ,z,t) u ( ϕ,z,t) 3d-dynamics u ( λ, ϕ,z,t) = u ( ϕ,z,t) + u'( λ, ϕ,z,t)

12 Dynamical aspects of the Earth s atmosphere Zwischenjährliche Dynamical variability Variabilität of the stratosphere in der Stratosphäre in winter Seasonal evolution of stratospheric North Pole temperature

13 Dynamical aspects of the Earth s atmosphere Sources of dynamical variability ab in the Earth s atmosphere e I Excitation of large-scale Planetary waves Rossby waves Kelvin waves at the surface by orography land-sea contrast or in-situ atmospheric instability stationary or transient dependent on ω Laboratory experiments in a water tank with different rotational speed (Hide and Mason, 1975)

14 Dynamical aspects of the Earth s atmosphere Sources of dynamical variability in the Earth s atmosphere II Excitation of Gravity waves at the surface by orography in the atmosphere by convection shear winds

15 Equator-to-Pole Transport Cells Earth Polar Ferrel H Hadley (not to scale)

16 Dynamical aspects of the Earth s atmosphere Breaking planetary and gravity waves in the upper stratosphere drive the mean meridional circulation. Wave driven pump Shaded: Area with strong wave dissipation: Surf zone in the stratosphere in winter Holton und Alexander (2000) Equator Winter Pole

17 Dynamical aspects of the Earth s atmosphere Mean meridional circulation (MMC) Brewer-Dobson-Zirkulation (BDC) 70km 10km summer winter The BDC describes the net meridional mass transport in the atmosphere.

18 Dynamical aspects of the Earth s atmosphere Transport characteristics from long-lived trace gases HALOE satellite data 1. Tropical upwelling 2 2. Downwelling at high latitudes 1 3. Flat gradients in surf-zone due to redistribution by waves 3 4. : Polar, subtropical transport barriers HF: Wasserstoff-Fluorid Quelle: Stratosphäre Randel (2001)

19 Dynamical aspects of the Earth s atmosphere Another example: Ozone SBUV: Jahresmittel von , Ozon (DU/km) Ozone is transported from photochemical source regions in the upper tropical stratosphere to high latitudes in the lower stratosphere by the BDC.

20 Dynamical aspects of the Earth s atmosphere Zunahme der Gesamtozonsäule in hohen Breiten im Winter infolge Transport mit der Brewer-Dobson-Zirkulation (Dobson et al., Proc. Roy. Soc. London, 1929)

21 Dynamical aspects of the Earth s atmosphere Specific transport phenomena: The tropical QBO QBO: Quasi-biennial Oscillation of the tropical zonal wind in the middle stratosphere F d f th l t h Forced from the lower atmosphere by vertically propagating waves

22 Transport of trace gases with the atmospheric circulation WMO (1999)

23 Dynamical regimes es of other planets

24 Mars, Venus and others

25 VENUS EARTH - MARS Planetary Data Radius(km) Mass (kg) 4.87x x x10 23 Gravity (m/s2) Distance from Sun (AU) Obliquity (degrees) Length Year (Earth days) Length Day (Earth days) Number of Satellites Eccentricity Inclination (degrees) Visual Albedo Surface T (K) Surface P (bars)

26

27 Mars Orbit and Climate 1.38AU 1.65AU 45% change in solar input Mars is ~half the size of Earth and only ~11% of the mass! Weaker gravity has resulted in stronger escape hence a thin atmosphere. Mars orbit is more eccentric compared with the Earth so strong climate effects are expected.

28 Mars asob Orbit and dclimate ae Mars Orbit not only eccentric but also large variations in obliquity strong climate changes

29 Martian a Surface Mercator ecao View Olympus Mons Phoenix Alba Vastitas Borealis (~-4km) Patera Viking 2 Viking 1 Pathfinder Opportunity Tharsis (~+4km) Syrtis Major Hellas Basin Elysium Spirit Argyre Mars Orbiter Surface Altimeter (MOLA)

30 Mars Atmosphere

31 Mars: Atmospheric T-P Profile Atmosphere is thin (6mb) and cold (~250K) at surface Water frozen out of atmosphere Dusty Climate Mainly CO 2 (95.3%) Seasonal Pressure Cycle

32 Martian Seasonal Pressure Cycle CO 2 condenses in polar regions in winter leads to 20% variation in atmospheric pressure (cf 1% on Earth)

33 Martian Atmospheric Dynamics Important Principles No ocean (strong heat sink on Earth) strong cyclical variations e.g. temperature driven by changes in solar insolation and Obliquity and eccentricity are strongly variable affect Martian climate

34 Martian Daily Temperature Cycle Driven by solar input and radiative properties of surface.

35 Seasonal Temperature Changes on Mars VIKING 1 (~20N) VIKING 2 (~50N)

36 Seasonal Temperature Changes on Mars Large Dust Storm causes weakening of T amplitude VIKING 1 (~20N) VIKING 2 (~50N)

37 Hadley Cell on Mars smaller Coriolis force single, giant Hadley cell can form Faster on Mars Mars 100 days Earth 1 year Cell is slowed by heat absorption from oceans on Earth

38 smaller Coriolis force single, giant Hadley cell can form Mars Faster on Mars Mars 100 days Earth 1 year Cell is slowed by heat absorption from oceans on Earth

39 Modelling the Martian Hadley Cell Modern Mars Vary Orbit Parameters Remove Orography BIGGEST EFFECT! Richardson and Wilson (2002)

40 3D (GCM) Zonal mean Temperature of Mars Winter Summer Warm region arises due to atmospheric waves formed near the surface travelling polewards, breaking and depositing heat Source: Mars Atmosphere Observation and Modelling

41 GCM Simulation of Mars zonal wind strong wintertime polar vortex develops due to meridional flow Summer Winter

42 Atmospheric Dynamics on Venus Cyclostrophic flow Coriolis force weak - Pressure force balanced by centrifugal force Centrifugal Force Wind Pressure Gradient Force Coriolis and small Centrifugal Force Wind Pressure Gradient Force Venus Earth Zonal Cyclostrophic Wind Zonal Geostrophic Wind

43 Meridional Transport on Earth and Venus LESS HEAT ABSORBED BY VENUS BECAUSE ALBEDO=0.6 (Earth=0.4) Source: LASP Weak meridional heat gradient on Venus

44 Venus N-S transport from single giant Hadley Cell Earth fast rotation strong Coriolis force breaks circulation into three cells (Hadley, Ferrel, Polar) Venus slow rotation, thick atmosphere single Hadley cell is stable

45 Venus N-S transport from single giant Hadley Cell Earth fast rotation strong Coriolis force breaks circulation into three cells (Hadley, Ferrel, Polar) Venus Express Mission has updated knowledge in this region -the Hadley cell extends only up to -60 o THEN there is a double (dipole) vortex Venus slow rotation, thick atmosphere single Hadley cell is stable

46 Venus Vertically overlapping cells Twin polar vortices Superrotation of atmosphere Source: Ruslike 2007

47 Venus has superrotation wind slower near poles E W Winds ~100ms-1 at ~60km 60 times faster than planet in tropics i.e. SUPERROTATION Weak surface winds Strong winds at cloud tops in tropics

48 Studies of Venus Superrotation ti Problem to simulate superrotation needs a mechanism to transfer angular momentum from surface to atmosphere. Difficult for models!!! Some examples of model studies: Hourdin et al. (1992) produced superrotation in non-forced LMD (French) GCM Del Genio et al. (1993) superrotation from upper troposphere cloud radiative effect in GCM

49 Titan Source: Cassini Source:Huygens

50 Why study Titan s atmosphere? Only body in solar system other than Earth with thick (1.5 bar) nitrogen atmosphere Conditions are thought to resemble the early Earth so understanding Titan could shed light on earthlike atmosphere development and conditions favouring life

51 Titan's atmosphere Surface T=94K Surface P=1.5bar 97% N 2 3% CH 4 Resembles Early Earth

52 Titan GCM Studies (Superrotation in upper atmosphere) Source: Samuelson (2002)

53 Summary of atmospheric dynamical regimes

54 Saturn s Hexagonal Vortex at high Northern latitudes Feature is long-lived observed by Voyager and recently by Cassini Source: Cassini

55 Jupiter s global atmospheric dynamics Temperature (K) Values oscillate with 4-5 year period (Quasi Quadrennial Oscillation (QQO) equator colder than mid-lats! strong jet Zonal Wind (u,ms -1 ) from thermal wind relation (i.e. u proportional to dt/dlat) Source: Flasar et al. (2004) Cassini data

56 Jupiter s hotspot at 1mb 1mb HOTSPOT Purple = 160K Red = 185K 4mb NO HOTSPOT O Source: Flasar et al. (2004) Cassini data

57 Atmospheric Transport on the Early Earth What do we know: Thick atmosphere (~1-10 bar) High CO 2 (~x100 present from sediment data) ~30% weaker sun (stellar models) (but UV probably higher) CO, H 2, H 2 O, CH 4 from previous model studies Earth spun about 50% faster Moon was up to 15 times closer ATMOSPHERE PROBABLY V. DYNAMICALLY PERTURBED!!