Power to the Looney-toons!

i. The Earth heat budgetii.The Ocean/Atmosphere coupling

OceanographyOceanographyLecture 11Lecture 11

What do we have left?

a.a. The structure of the OceansThe structure of the Oceansi.i. The Earth heat budget &The Earth heat budget &

Ocean/Atmosphere couplingOcean/Atmosphere couplingc.c. The Ocean in motionThe Ocean in motion

b.b. Horizontal and vertical circulationHorizontal and vertical circulationc.c. Global circulationGlobal circulation

d.d. Climate VariabilityClimate Variability1)1) El El Niño-Southern Niño-Southern OscillationOscillation2)2) North Atlantic OscillationNorth Atlantic Oscillation

e.e. Chemistry of SeawaterChemistry of Seawaterf.f. Biogeochemistry and Primary ProductivityBiogeochemistry and Primary Productivity

Radiation and temperatureRadiation and temperatureAny object with a temperature above absolute Any object with a temperature above absolute ““00””

1)1) Emits radiation!Emits radiation!2)2) At a wavelength directly proportional to itsAt a wavelength directly proportional to its

temperature (the higher the temperature, thetemperature (the higher the temperature, thefaster the electrons vibrate)faster the electrons vibrate)

Stefan-BoltzmannStefan-Boltzmann LawLaw

E = E = !!TT44

E is the maximum emitted energy per mE is the maximum emitted energy per m22

! ! is a constant (5.67x10is a constant (5.67x10-8-8 W/m W/m22.k.k44))T is the objectT is the object’’s surface temperature (in °Kelvin)s surface temperature (in °Kelvin)

Radiation and temperatureRadiation and temperatureAny object with a temperature above absolute Any object with a temperature above absolute ““00””

3)3) Emits radiation at a wavelength inverselyEmits radiation at a wavelength inverselyproportional to its temperature (the higher theproportional to its temperature (the higher theenergy, the shorter the wavelength)energy, the shorter the wavelength)

WienWien’’s s LawLaw

""maxmax = Constant/T= Constant/T

""maxmax is the maximum wavelength emittedis the maximum wavelength emittedThe constant is ~3000 The constant is ~3000 µµm Km K

Radiation Spectra of Sun and EarthRadiation Spectra of Sun and Earth

""maxmax Sun = 3000 Sun = 3000 µµmKmK/6000 K = 0.5 /6000 K = 0.5 µµmm

""maxmax Earth = 3000 Earth = 3000 µµmKmK/300 K = 10 /300 K = 10 µµmm•• 44% of the sun44% of the sun’’s radiation in the s radiation in the visible regionvisible region (0.4-0.7 (0.4-0.7 µµm)m)•• 7% as UV and 37% as near IR7% as UV and 37% as near IR•• 88% of the sun energy is radiated at wavelength <1.588% of the sun energy is radiated at wavelength <1.5µµmm•• While the Earth emits in the far IR: 10 While the Earth emits in the far IR: 10 µµmm

Fate of RadiationFate of RadiationDependent on the medium it is traveling throughDependent on the medium it is traveling through

Radiation absorption and emissionRadiation absorption and emissionRadiation may be absorbed by many types ofRadiation may be absorbed by many types ofmaterials. It turns out that all objects are able tomaterials. It turns out that all objects are able toemit radiation at all wavelengths and similarlyemit radiation at all wavelengths and similarlyabsorb all types of radiation.absorb all types of radiation.

The energy is not lost but rather converted toThe energy is not lost but rather converted tosome type of internal energy within the absorbingsome type of internal energy within the absorbingmediummedium

Any object that is a perfect absorber and perfectAny object that is a perfect absorber and perfectemitter is called a emitter is called a blackbodyblackbody

The Sun and Earth both absorb and emit radiationThe Sun and Earth both absorb and emit radiationclose to ~100% efficiency close to ~100% efficiency !! blackbodiesblackbodies

Radiation absorption and emissionRadiation absorption and emissionSo the sun So the sun ““shinesshines”” and the Earth and the Earth ““bakesbakes””but reallybut really…… The Earth also The Earth also ““looseslooses”” its energy as fast its energy as fastas it gains it (so it as it gains it (so it ““shinesshines”” in its own right) in its own right)

Radiating in the IR portion of the spectrum Radiating in the IR portion of the spectrum !! Long Longwavelength, low radiation energywavelength, low radiation energy

Radiative Radiative equilibrium temperatureequilibrium temperature

The state at which absorption of solarThe state at which absorption of solarradiation = emission of IR radiation:radiation = emission of IR radiation:

255 255 °°K = -18K = -18°°CC

But the actual T° ofBut the actual T° ofEarth is much higherEarth is much higherthan thatthan that

288 288 °°K = +15K = +15°°CC

How can we explain theHow can we explain the+33+33°° difference? difference?

Radiation absorption and emissionRadiation absorption and emissionNot all substances on Earth behave as Not all substances on Earth behave as blackbodiesblackbodiesMost substances are selective absorbers (i.e. glassMost substances are selective absorbers (i.e. glass!! UV and IR) UV and IR)

Objects that selectively absorb radiation alsoObjects that selectively absorb radiation alsoselectively re-emit radiation at the sameselectively re-emit radiation at the samewavelength: wavelength: KirchhoffKirchhoff’’s s LawLawGood absorbers are good emitters at a particular Good absorbers are good emitters at a particular !!

Specifically for gasesSpecifically for gases!!

Selective absorption of radiation in theSelective absorption of radiation in theAtmosphereAtmosphere

OO22 and O and O33 absorb almost 100% of the UV radiation absorb almost 100% of the UV radiationof of "" < 0.3 < 0.3 µµm.m.

0.1 0.3 0.5 0.7 1 5 10 15 20

HH22O and COO and CO22 are strong absorbers of IR radiation are strong absorbers of IR radiationand poor absorbers of visible radiation.and poor absorbers of visible radiation.

0.1 0.3 0.5 0.7 1 5 10 15 20

0.1 0.3 0.5 0.7 1 5 10 15 20

CHCH44 and N and N22O, and OO, and O33 are also strong absorbers of are also strong absorbers ofIR radiationIR radiation

As these gases absorb IR emitted by the EarthAs these gases absorb IR emitted by the Earth’’sssurface (remember that most of it comes from Earth),surface (remember that most of it comes from Earth),they gain kinetic energy they gain kinetic energy !! Kinetic energy transferredKinetic energy transferredto Oto O22 and N and N2 2 !! temperature temperature ""

Atmospheric greenhouse effectAtmospheric greenhouse effect

H2O – CO2– CH4 – NO2 – CFC

Atmos. window

Earth Energy BalanceEarth Energy BalanceSolar constant ~1370 W/mSolar constant ~1370 W/m22 caught by a caught by a ““discdisc”” facing facingthe Sun and retransmitted to the whole Earth (sphere):the Sun and retransmitted to the whole Earth (sphere):

SScc x x ##rr22/4/4##rr22 = S = Scc/4 = 340 W/m/4 = 340 W/m22

The EarthThe Earth’’s heat budgets heat budget((Do we have a surplus?Do we have a surplus?

Is it going to Social Security?)Is it going to Social Security?)

$Q = Qs + Qb + Qh + Qe + Qv =? 0

Qs = Solar radiation

Qb = back radiation

Qh = Thermal Cond

Qe = Evaporation

Qv = Advection

Earth Energy BalanceEarth Energy BalanceAlthough average T vary seasonally and spatially, theAlthough average T vary seasonally and spatially, theEarthEarth’’s overall T changes only slightly over the years s overall T changes only slightly over the years !!must return to space the same amount of energy itmust return to space the same amount of energy itabsorbed. Total energy input = 100 units (per unit time)absorbed. Total energy input = 100 units (per unit time)

Earth Energy BalanceEarth Energy BalanceMore detailsMore details……

Where are the other 30%?

The Heat Budget! The wavelength of energy

radiated from a body is inverselyproportional to the temperatureof the body: ! Sun radiates atshorter wavelengths (0.5 µm;visible) than the Earth (10 µm;infrared)

! The average temperature ofEarth’s surface and the lowerlayer of atmosphere is ~15°C.However, if the atmospherecontained no water vapor, CO2, orCH4, the temperature of theEarth would be about -18°C!

! The greenhouse effect: H2Ovapor (73% or 24°C); CO2 (21% or7°C); CH4 (6% or 2°C)

Balanced Budget?Incoming (65% of Qs)! 35% “bounce” off Earth surface and Atmosphere (albedo)! 17% are absorbed by the atmosphere! 48% are absorbed by EarthOutgoing! 8% are emitted directly as Earth’s back radiation! 27% are emitted directly by the atmosphere! 19% transferred by conduction! 46% transferred by evaporation!

Earth’s Seasons – “Split” in energy inputUniform heating?

! Earth is a “sphere”! (what else is new…)

! Tilt in the Earth’s axis

Uniform heating?! Equator to pole change in incoming radiation ! %Heating! Seasonal change in incoming radiation ! %Heating

Earth’s energy budget is initially at disequilibrium!

Amount of solar radiationreceived annually at the Earth’s

surface

Earth’s Heat Budget

Qs>Qb Qs<Qb Qs<Qb

Our AtmosphereOur Atmosphere• Extremely dynamic ! system driven by solar

heating. Composed of different air packets atdifferent temperatures.

• Warm gas expands, lowering density and leadingto pressure differences (" wind)

The Atmosphere starts Moving: Simplified Global Circulation Patterns

N

S

• Low-pressure zone: Equator• High-pressure zones: PolesSimple circulation cell in each

hemisphere with:! Surface winds directed

towards the Equator! Upper-level winds directed

towards the poles! That’s it!!! That’s it????

The Coriolis Effect:

! The Earth rotates upon its axis! The surface velocity increases from 0 km/h at the poles…! To 1600 km/h at the equator!

! One revolution every 24 hours…

1600 km/h

800 km/h

Global Circulation Patterns:1) Atmosphere

N

S

Atmospheric circulation resultsfrom

1) Earth’s rotation and

2) differential heating atsurface and in atmosphere

!this produces prevailing windsand latitudinal belts of high/lowpressure

!Earth is essentially dividedinto two atmospheric sections(red line)

!So, is this it?

Global Circulation Patterns:2) Oceans

Surface oceanic circulationresults from

• 1) Prevailing winds(differential heating atsurface and in atmosphere)and

• 2) Earth’s rotation! this produces prevailing

currents and heat transfer(High Heat Capacity =Delayed Response Time)

! Evaporation is the largesttransfer flux of energy(heat) from the ocean to theatmosphere

The Gulf Stream

Global Circulation Patterns:3) Atmosphere-Ocean “coupling”

!Low latitudes: Oceans!High latitudes: Atmosphere

Atmosphere-Ocean “coupling”

!Atmosphere – Transfer of moisture to theatmosphere (heat released in higher latitudesas water condenses!)

Atmosphere-Ocean “coupling”

!Atmosphere – Transfer of moisture tothe atmosphere: Hurricanes!

www.weather.com

In summary

Amount of solar radiation received annually at the Earth’s surface

Latitudinal Differences in Energy

Latitudinal Differences in Salinity

Latitudinal Differences in Density Structure of the Oceans

T has a much greaterimpact than S onDensity!

Light

Heavy

Atmospheric – Wind patterns

High/Low Pressure systems: Heat capacity!

July

Atmospheric – Wind patterns

High/Low Pressure systems: Heat capacity!

January

Atmospheric – Wind patterns

High/Low Pressure systems: Wind generation

January

Easterlies

Westerlies

Westerlies

Easterlies