¾at hä d ik atmosphären: dynamik - dlr.de · sources of dynamical variability in the earth‘s...

Ringvorlesung „Planeten und Leben im Überblick“, TU Berlin, 28. Mai 2009

ÜRingvorlesung „Planeten und Leben im Überblick“

Oberflächen …..

At hä D ikWasser …..Atmosphären: DynamikAtmosphären: ChemieAtmosphären: Chemie

Atmosphären: Klimaentwicklungp gInneres …..

Institut für Meteorologie, Freie Universität Berlin


Atmosphären: Dynamik

Dynamik und TransportprozesseDynamik und Transportprozesse in Planetenatmosphären

Prof Dr Ulrike LangematzProf. Dr. Ulrike LangematzInstitut für Meteorologie, Freie Universität Berlin

[email protected]

Dr. Lee GrenfellZentrum für Astronomie und Astrophysik, Technische Universität Berlin


Zentrum für Astronomie und Astrophysik, Technische Universität Berlin

D i l tDynamical aspects f ‘of the Earth‘s

atmosphere

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.1 The sun as energy source

Dynamical aspects of the Earth‘s atmosphere

Differential solar heating1. The sun as energy source Differential solar heatingTemperature gradients

Dynamics

Factors affecting dynamics:• Orbital parameters

11-year Schwabe-Zyklus• Orbital parameters • Rotation of planet • Variability of energy input

0 1 %0.1 %Maunder Minimum

http://www.pmodwrc.ch/solar_const/solar_const.html1645-1715 Hoyt und Schatten, 1993, updated

2 Chemical composition of Earth‘s atmosphere


Substance Fraction [V%]

2. Chemical composition of Earth s atmosphere

Nitrogen (N2) 78,08

Oxygen (O2) 20,95

Argon (Ar) 0,93g ( ) ,

Carbondioxid (CO2) 0,033

Neon (Ne) (+ Noble gases) 90%

10%dry

Factors affecting dynamics:moist• chemical compositionJanuary, ppmv


Short wave solar heating ratedue to absorption by ozone and

Temperaturein °Cdue to absorption by ozone and

molecular oxygenin K/day

in C

January

KW

W

KK

K


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

Theoretical concept of zonal mean background state with imposed

summer winter

Theoretical concept of zonal mean background state with imposed dynamical effects by wavelike disturbances

Temperature and zonal windDynamical aspects of the Earth‘s atmosphere

E

Temperature and zonal wind

January, zonal means

How does the corresponding zonal wind field look like?

W ESPARC climatology(http://sparc.sunysb.edu)

Polar night jet

With the assumption of geostrophic balance: WE

Polar night jet

Equilibrium between Coriolis force (due to Earth rotation) and pressure gradient force in the large scale):

W

Egradient force in the large scale):

Geostrophic wind:

u = −1/(ρf) δp/ δyu 1/(ρf) δp/ δy

Thermal wind:

δ /δ δT/δ

W W

δu/δz = ~ − δT/δy

Stratospheric mean circulationDynamical aspects of the Earth‘s atmosphere

winter

Geopotential height, long-term mean, northern hemisphere

Stratospheric mean circulation

summerwinter summer

H

T H

Episodic occurrences of Major Stratospheric Warmings


Episodic occurrences of Major Stratospheric Warmings


Arctic high in summer Stratospheric warming im Januar 2006

2d-approximation valid 3d-dynamics)tz(u)tz(u ϕ≈ϕλ )tz('u)tz(u)tz(u ϕλ+ϕ=ϕλ


)t,z,(u)t,z,,(u ϕ≈ϕλ )t,z,,(u)t,z,(u)t,z,,(u ϕλ+ϕ=ϕλ

Zwischenjährliche Variabilität in der StratosphäreDynamical variability of the stratosphere in winterDynamical aspects of the Earth‘s atmosphere

j py y pSeasonal evolution of stratospheric North Pole temperature

Sources of dynamical variability in the Earth‘s atmosphere I


Sou ces o dy a ca a ab y e a s a osp e e

Excitation of large-scalePlanetary wavesPlanetary wavesRossby wavesKelvin wavesKelvin waves

at the surface byh• orography

• land-sea contrast

or in-situ atmospheric instability

stationary or transient

dependent on ωdependent on ωLaboratory experiments in a water tank with different rotational speed(Hide and Mason, 1975)

Sources of dynamical variability in the Earth‘s atmosphere II


Sources of dynamical variability in the Earth s atmosphere II

Excitation of

Gravity wavesGravity waves

at the surface by• orography• orography

in the atmosphere byconvection• convection

• shear winds

Equator-to-Pole Transport Cells

PolarE th FerrelEarth

H dlHadley(not to scale)


Shaded:Area with strong wave dissipation: Surf zone

Breaking planetary and gravity waves in

Wave driven pump Surf zoneand gravity waves in

the upper stratosphere drive the

pump

mean meridional circulation.

in the stratosphere in winter

Holton und Alexander (2000)

Equator Winter Pole

M idi l i l ti (MMC)


Mean meridional circulation (MMC)Brewer-Dobson-Zirkulation (BDC)

70km

10km10km

summer winter

The BDC describes the net meridional mass transport in the atmosphere.

Transport characteristics from long-lived trace gasesDynamical aspects of the Earth‘s atmosphere

p g g

HALOE t llit d tHALOE satellite data

2

1

1. Tropical upwelling

2. Downwelling at high latitudes

3

latitudes

3. Flat gradients in surf-zone due to redistribution by waves

4. : Polar, subtropical transport barriers

Randel (2001)HF: Wasserstoff-Fluorid

Quelle: Stratosphäre

transport barriers

Randel (2001)Quelle: Stratosphäre

Another example: Ozone


Another example: OzoneSBUV: Jahresmittel von 1980-89, 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.

Zunahme der Gesamtozonsäule in hohen Breiten im WinterDynamical aspects of the Earth‘s atmosphere

infolge Transport mit der Brewer-Dobson-Zirkulation(Dobson et al., Proc. Roy. Soc. London, 1929)

Specific transport


Specific transport phenomena: The tropical QBOThe tropical QBO

QBO: Quasi-biennial Oscillation

of the tropical zonal wind in the middle stratosphere

F d f th l t hForced from the lower atmosphere by vertically propagating waves

Transport of trace gases with the atmospheric circulationp g p

WMO (1999)WMO (1999)


Dynamical regimes y a ca eg esof other planetsof other planets



Mars Venus andMars, Venus and othersothers



VENUS – EARTH - MARS

Planetary Data

Radius(km) 6052 6360 3395Mass (kg) 4.87x1024 5.97x1024 6.42x1023

Gravity (m/s2) 8 87 9 81 3 71Gravity (m/s2) 8.87 9.81 3.71Distance from Sun (AU) 0.72 1.0 1.52Obliquity (degrees) 177.4 23 25.2L th Y (E th d ) 224 7 365 25 687 0Length Year (Earth days) 224.7 365.25 687.0Length Day (Earth days) -243.0 1.0 1.03Number of Satellites 0 1 2Eccentricity 0.0067 0.0167 0.093Inclination (degrees) 3.4 0.0 1.9Visual Albedo 0.65 0.4 0.15


Surface T (K) 735 288 220Surface P (bars) 93 1.0 0.006


Mars Orbit and ClimateMars Orbit and Climate

Mars is ~half the size of Earth and only ~11% of the mass! Weaker gravity has resulted in stronger escape

1.38AU 1.65AU

resulted in stronger escape hence a thin atmosphere.

Mars’ orbit is more eccentric45% change

Mars orbit is more eccentric compared with the Earth so strong climate effects are

in solar input

gexpected.



Mars Orbit and Climatea s O b a d C a e

Mars Orbit not only eccentric but also large


variations in obliquity – strong climate changes


Martian Surface – Mercator Viewa a Su ace e ca o e

Vastitas Borealis (~-4km)OlympusAlbaPhoenix ( )Olympus

MonsPatera

Viking 2

ElysiumViking 1

SyrtisPathfinder

Tharsis (~+4km)Hellas

SpiritMajor

Opportunity

Argyre

HellasBasin

gy


Mars Orbiter Surface Altimeter (MOLA)


Mars’ Atmosphere



Mars: Atmospheric T P ProfileMars: Atmospheric T-P Profile

Atmosphere is thin (6mb) and cold (~250K) at surface

Water frozen out of atmosphereatmosphere

Dusty Climate

Mainly CO2 (95.3%)

Seasonal Pressure Cycle



Martian Seasonal Pressure Cycley

CO2 condenses in polar regions in winter leads to


20% variation in atmospheric pressure (cf 1% on Earth)


M ti At h i D iMartian Atmospheric Dynamics

Important Principles

No ocean (strong heat sink on Earth)strong cyclical variations

e g temperature driven by changes ine.g. temperature driven by changes insolar insolation and

Obliquity and eccentricity are strongly variable affect Martian climate



Martian Daily Temperature CycleMartian Daily Temperature Cycle

Driven by solar input and radiative properties of surface.



Seasonal Temperature Changes on Mars

VIKING 1 (~20N)

VIKING 2 (~50N)



Seasonal Temperature Changes on MarsLarge Dust Storm causes weakening of T amplitude

Seasonal Temperature Changes on Mars

VIKING 1 (~20N)

VIKING 2 (~50N)



Hadley Cell on MarsHadley Cell on Mars

• smaller Coriolis force• smaller Coriolis force• single, giant Hadley cellcan form

• Faster on MarsMars – 100 daysEarth – 1 year

Cell is “slowed” byheat absorption fromheat absorption fromoceans on Earth


Mars• smaller Coriolis force• single giant Hadley cell

Mars• single, giant Hadley cellcan form

• Faster on MarsMars – 100 daysEarth – 1 year

Cell is “slowed” byheat absorption fromheat absorption fromoceans on Earth

Ringvorlesung „Planeten und Leben im Überblick“, TU Berlin, 28. Mai 2009Modelling the Martian Hadley Cell

Modern Mars

Vary Orbit Parameters

R O hRemove OrographyBIGGEST EFFECT!

Institut für Meteorologie, Freie Universität Berlin Richardson and Wilson (2002)


3D (GCM) Zonal mean Temperature of Mars3D (GCM) Zonal mean Temperature of Mars

W i iWarm region arisesdue to atmospheric waves formed near the surfaceformed near the surfacetravelling polewards,breaking and depositing heat

Winter Summer

Source: Mars Atmosphere Observation and Modelling


Source: Mars Atmosphere Observation and Modelling


GCM Si l ti f M l i dGCM Simulation of Mars zonal wind

strong wintertimepolar vortex developspolar vortex developsdue to meridional flow

WinterSummer


WinterSummer


Atmospheric Dynamics on VenusAtmospheric Dynamics on

Cyclostrophic flow – Coriolis force weak -

VenusCyclostrophic flow Coriolis force weak Pressure force balanced by centrifugal force

CentrifugalForce

Coriolis and small CentrifugalF

Wind

PressureGradient Force

Wind

Force PressureGradient Force

d

V E thVenusZonal Cyclostrophic Wind

EarthZonal Geostrophic Wind



Meridional Transport on Earth and VenusMeridional Transport on Earth and Venus

LESS HEAT ABSORBED BY VENUSLESS HEAT ABSORBED BY VENUSBECAUSE ALBEDO=0.6 (Earth=0.4)


Weak meridional heat gradient on VenusSource: LASP


Venus N-S transport from single giant Hadley Cell

Earth – fast rotationt C i li fstrong Coriolis force

“breaks” circulationinto three cells(Hadley, Ferrel, Polar)

Venus slow rotationVenus – slow rotation,thick atmosphere – singleHadley cell is stabley



Venus N-S transport from single giant Hadley Cell

Earth – fast rotationt C i li fstrong Coriolis force

“breaks” circulationinto three cells(Hadley, Ferrel, Polar)

Venus slow rotationVenus – slow rotation,thick atmosphere – singleHadley cell is stable

Venus Express Missionhas updated knowledge in this region y-the Hadley cell extends only up to-60o THEN there is a double (dipole) vortex


Venus e us

• Vertically overlappingcellscells

• Twin polar vortices• Superrotation ofatmosphere

Source: Ruslike 2007


Venus has “superrotation”Venus has superrotation

wind slower near poles

St i d

E W Winds ~100ms-1 at

Strong windsat cloud topsin tropicsE W Winds 100ms-1 at

~60km 60 timesfaster than planet in tropics

Weak surfacewinds

p

tropicsi.e. SUPERROTATION

winds



St di f V ’ S t tiStudies of Venus’ Superrotation

Problem – to simulate superrotation needs a mechanismto transfer angular momentum from surface to atmosphere.Difficult for models!!! Some examples of model studies:

• Hourdin et al (1992) – produced superrotation inHourdin et al. (1992) produced superrotation innon-forced LMD (French) GCM

•Del Genio et al. (1993) – superrotation from upper tropospherecloud radiative effect in GCM



Titan


Source: Cassini Source:Huygens


Why study Titan’s atmosphere?

Only body in solar system other than Earth withOnly 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 andearthlike atmosphere development and conditions favouring life



Titan's atmosphereTitan s atmosphere

Surface T=94KSurface T 94KSurface P=1.5bar97% N23% CH4

Resembles EarlyResembles Early Earth



Titan GCM Studies

(Superrotation in upper atmosphere)( p pp p )

Source: Samuelson (2002)


Source: Samuelson (2002)


Summary of atmospheric dynamical regimesy p y g



Saturn’s Hexagonal Vortex at high Northern latitudes…g g

S CSource: Cassini

Feature is long-lived


observed by Voyager and recently by Cassini

Jupiter’s global atmospheric dynamicsTemperature (K)Temperature (K)

Values oscillate with4 i d (Q i4-5 year period (QuasiQuadrennial Oscillation (QQO)

equator colder thanmid-lats!

(QQO)

Zonal Wind (u,ms-1)

mid-lats!

( )from thermal windrelation (i.e. u

proportional to dT/dlat)

Source:Fl t l (2004)

proportional to dT/dlat)strong jet

Flasar et al. (2004)Cassini data


Jupiter’s hotspot at 1mbat 1mb

1mbHOTSPOT Purple = 160K

Red = 185KRed = 185K

SSource:Flasar et al. (2004)

Cassini data4mb

NO HOTSPOT


O O S O

Atmospheric Transport on the Early Earthy

What do we know:

• Thick atmosphere (~1-10 bar)• High CO2 (~x100 present from sediment data)• ~30% weaker sun (stellar models) (but UV probably higher)

CO H H O CH f i d l t di• CO, H2, H2O, CH4 from previous model studies• Earth spun about 50% faster

Moon was up to 15 times closer• Moon was up to 15 times closer

ATMOSPHERE PROBABLY V DYNAMICALLY PERTURBED!!ATMOSPHERE PROBABLY V. DYNAMICALLY PERTURBED!!

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