Chapter 2

Energy Balance in ClimatologyAtmosphere gets most of it’s energy from the sun

Energy is concentrated in certain regions

must be moved from one location to another

Transference of Energy (E) is done by:

Conduction- E transfer by molecular contact

Convection- E transfer by motion

Radiation- E transfer via electromagnetic transference

Chapter 2

Energy Balance in ClimatologyAtmosphere gets most of it’s energy from the sun

Energy is concentrated in certain regions

must be moved from one location to another

Transference of Energy (E) is done by:

Conduction- E transfer by molecular contact

Convection- E transfer by motion

Radiation- E transfer via electromagnetic transference

Kinds of Energy

Radiation- the emission of energy on the form of waves

Kinetic- energy due to motion = 1/2m x v2

Potential- Energy stored as position potentially converted to Kinetic Energy

Chemical- Energy used or released in chemical reactions

Atomic- Energy released from an atomic nucleus at the expense of its mass

Electrical- Energy exerted as a force on objects with an electrical charge

Heat- aggregate energy of motions of atoms and molecules

Kinds of Energy

Radiation- the emission of energy on the form of waves

Kinetic- energy due to motion = 1/2m x v2

Potential- Energy stored as position potentially converted to Kinetic Energy

Chemical- Energy used or released in chemical reactions

Atomic- Energy released from an atomic nucleus at the expense of its mass

Electrical- Energy exerted as a force on objects with an electrical charge

Heat- aggregate energy of motions of atoms and molecules

Sun Sunlight Earth’s Surface Terrestrial

Atomic Energy

Radiation(all

waves)

Heat Radiation(longwave)

Sunlight Photosynthesis

Food chain

Radiation Chemical energy

Chemical energy

Water vapor Raindrop falling

Friction with air

Potential Energy

Kinetic Energy Heat

Solar Radiation: The driving factorSolar Radiation: The driving factor• • Radiation (ElectromagneticRadiation (Electromagnetic

energy) released, absorbed &energy) released, absorbed &reflected by all thingsreflected by all things

• • travels as both a particle andtravels as both a particle and

a wavea wave

• • is affected by is affected by

-- gravity, magnetism, andgravity, magnetism, and

atmosphere composition,atmosphere composition,distance, angle of incidencedistance, angle of incidence

• • provides Earth with anprovides Earth with an

external source of energyexternal source of energy

Wavelength and frequency are inversely related to one another Wavelength

(1/Frequency

Nature of radiative energy (Radiation)electromagnetic travels as waves and also acts like particleAll things radiate energy

a function of Temperature

Stephan-Boltzman’s Law

F = T 4

Where F is radiation Fluxis a constant 5.67 x 10-8 W/m2K4

T is the temperature in ° KelvinThe hotter the object, the more energy it radiatesF = (5.67 x 10-8) x (6000)4 = 73,400,000 W/ m2 :SunF = (5.67 x 10-8) x (288)4 = 390 W/ m2 :Earth

Nature of radiative energy (Radiation)electromagnetic travels as waves and also acts like particleAll things radiate energy

a function of Temperature

Stephan-Boltzman’s Law

F = T 4

Where F is radiation Fluxis a constant 5.67 x 10-8 W/m2K4

T is the temperature in ° KelvinThe hotter the object, the more energy it radiatesF = (5.67 x 10-8) x (6000)4 = 73,400,000 W/ m2 :SunF = (5.67 x 10-8) x (288)4 = 390 W/ m2 :Earth

In general, temperature of emitting body controls wavelength of outgoing energy

hotter = shorter cooler = longer

Wein’s Lawallows us to predict which

wavelength will be most abundant.max= 2897/T

Example:Sun’s surface temperature is 6000° Kmax = 2897/6000 = 0.48mThus, most of sun’s energy should be at a wavelength of 0.48 m

In general, temperature of emitting body controls wavelength of outgoing energy

hotter = shorter cooler = longer

Wein’s Lawallows us to predict which

wavelength will be most abundant.max= 2897/T

Example:Sun’s surface temperature is 6000° Kmax = 2897/6000 = 0.48mThus, most of sun’s energy should be at a wavelength of 0.48 m

0.48

Solar StructureSun is a fusion reactor-smashes atoms of H into other atoms and makes new, heavier elements and releases a bunch of energy

H + H = He + a lot of energy

Has zones that are important to climatologyPhotosphere- visible part of the sun we see all the time (covered during a solar eclipse)Consists primarily of Hydrogen (90%) and Helium (10%)

This is where the 6000° K temperature comes from

Uneven heat distribution in the 300 km thick layer created by convection currents results in grainy appearance

Solar StructureSun is a fusion reactor-smashes atoms of H into other atoms and makes new, heavier elements and releases a bunch of energy

H + H = He + a lot of energy

Has zones that are important to climatologyPhotosphere- visible part of the sun we see all the time (covered during a solar eclipse)Consists primarily of Hydrogen (90%) and Helium (10%)

This is where the 6000° K temperature comes from

Uneven heat distribution in the 300 km thick layer created by convection currents results in grainy appearance

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

ChromosphereA wide (up to 1,000,000 Km) but variable zone of burning gases above the photosphere

The gases in this zone move at high velocities and travel outward from the Sun as the solar wind

Also the zone within which sun spots and solar flares occur

Sun spots are cooler regions on the Sun’s surface zones of intense magnetic disturbance

Flares are explosive eruptions of atomic particles and radiation that extend outward for millions of miles and can influence stuff 100’s of millions of miles away

ChromosphereA wide (up to 1,000,000 Km) but variable zone of burning gases above the photosphere

The gases in this zone move at high velocities and travel outward from the Sun as the solar wind

Also the zone within which sun spots and solar flares occur

Sun spots are cooler regions on the Sun’s surface zones of intense magnetic disturbance

Flares are explosive eruptions of atomic particles and radiation that extend outward for millions of miles and can influence stuff 100’s of millions of miles away

Solar Corona Solar Photosphere

Sun spots

What happens to solar radiation? It decreases with distance traveled outward

Inverse square law

Frec = F (1/d2)where F = radiation from Sun

Frec = Radiation received and d = distance from source

d is in astronomical unit (AU) or distance from Sun to Earth = 1

Our distance from the sun controls how much solar energy we get from the SunFrec is very small 1/2,000,000,000 of the total energy produced by the Sun

Several things can happen to that incoming energy

Reflection, Refraction, Scattering, Absorption

What happens to solar radiation? It decreases with distance traveled outward

Inverse square law

Frec = F (1/d2)where F = radiation from Sun

Frec = Radiation received and d = distance from source

d is in astronomical unit (AU) or distance from Sun to Earth = 1

Our distance from the sun controls how much solar energy we get from the SunFrec is very small 1/2,000,000,000 of the total energy produced by the Sun

Several things can happen to that incoming energy

Reflection, Refraction, Scattering, Absorption

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

How much energy does the Earth receive?

Imagine a sphere with a radius (d) the distance from the Earth to the center of the Sun = 1 AU

Earth--->

<---Sun<---Sun

<---Radius (d)<---Radius (d)

Position affects radiation too• Far away=less radiation

• Titled toward= more radiation• Tilted away=less radiation in North

• Titled toward= more radiation in North

Milankovitch Orbital variations

Eccentricity - change of Earth’s orbit around the Sun from a Circle to an Ellipse. Timeframe: 100,000 years

Obliquity- Change in the tilt of the Earth’s axis of daily rotation. Timeframe: 41,000 yrs

Precession- the wobble of earths tilt or the change in the timing of the tilt of the Earth that forces the northern hemisphere toward the sun- at perihelion vs aphelion 22,000 - to 26,000 years

These work with other systems in the earth to set the pace of climate change

Milankovitch Orbital variations

Eccentricity - change of Earth’s orbit around the Sun from a Circle to an Ellipse. Timeframe: 100,000 years

Obliquity- Change in the tilt of the Earth’s axis of daily rotation. Timeframe: 41,000 yrs

Precession- the wobble of earths tilt or the change in the timing of the tilt of the Earth that forces the northern hemisphere toward the sun- at perihelion vs aphelion 22,000 - to 26,000 years

These work with other systems in the earth to set the pace of climate change

Summer Solstice Winter Solstice

• Sun's energy at 90°

at Tropic of Cancer

• Sun overhead at noon

• Sun's energy at 90°

at Tropic of Capricorn

• Sun overhead at noon

> ~June 21 ~December 21

Albedo

• • A measure of the amount of reflected radiationA measure of the amount of reflected radiation

• • Some things reflect radiation better than othersSome things reflect radiation better than others

- - "dry" or "cold" Snow & Ice = high albedo"dry" or "cold" Snow & Ice = high albedo- - water = moderate for visible, low for infraredwater = moderate for visible, low for infrared- - plants= moderate for visibleplants= moderate for visible

• • Land absorbs and releases radiative energyLand absorbs and releases radiative energyquicker than waterquicker than water

Albedo = ________________incident radiationreflected radiation

*

Typical albedos of various surfaces to incoming solar radiation

Type of surface Percent reflected energy (Albedo)

Fresh Snow 75 - 95%

Old Snow 30 - 40%

Water

0° 99%

10° 35%

30° 6%

90° 2%

Clouds

Cumulus 70 - 90%

Stratus 60 - 84%

Cirrus 44 - 50%

Forest 5 - 20%

Grass 10 - 20%

Sand 35 - 45%

Plowed soil 5 - 25%

Crops 3 - 15%

Concrete 17 - 27%

Earth as a Planet 30%

Reflectionenergy is bounced away without being

absorbed or transformed

Scatteringenergy is diffused or scattered into different wavelengthsrelated to composition and thickness of

atmosphereAbsorption

some gases and aerosols capture (absorb) energy

energy is typically re-released as longer wavelength

radiative energyTransmissivity

The amount of radiation that actually gets through

to the surface

Reflectionenergy is bounced away without being

absorbed or transformed

Scatteringenergy is diffused or scattered into different wavelengthsrelated to composition and thickness of

atmosphereAbsorption

some gases and aerosols capture (absorb) energy

energy is typically re-released as longer wavelength

radiative energyTransmissivity

The amount of radiation that actually gets through

to the surface

Greenhouse effect

Seen as a bad thing by the public because of biased or poorly produced media coverage

Greenhouse effect is absolutely essential to Earth’s habitability

Without some means to absorb, block, scatter or transform energy, the Earth would be barren.

Atmosphere does all four things

Most important among these is absorption of longwave (Earth-reemitted or transformed) radiation

Various gases capture this energy which warms the Earth’s atmosphere

Greenhouse effect

Seen as a bad thing by the public because of biased or poorly produced media coverage

Greenhouse effect is absolutely essential to Earth’s habitability

Without some means to absorb, block, scatter or transform energy, the Earth would be barren.

Atmosphere does all four things

Most important among these is absorption of longwave (Earth-reemitted or transformed) radiation

Various gases capture this energy which warms the Earth’s atmosphere

Energy balance of Earth’s SurfaceInflow Outflow

Solar radiation 50 Earth radiation 114Sky radiation 96 Latent Heat 20total 146 Conduction 12

total 146

Energy balance of AtmosphereInflow Outflow

Solar Radiation 20 Radiation to space 63Condensation 20 Radiation to Surface 96Earth Radiation 107 total 159Conduction 12total 159

Energy Balance of EarthInflow Outflow

Solar radiation 100 Reflected Radiation 30total 100 Sky radiation to space 63

Earth radiation to space

7

total 100

Distribution of Radiation

• energy balance diagram