Energy Balance in Climatology

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• Chapter 2
• Energy Balance in Climatology
• Atmosphere gets most of its energy from the sun
• not directly though!
• Energy input is concentrated in certain regions
• must be moved from one location to another by one
  of earths systems
• Atmosphere (air) or hydrosphere (oceans)
• Transference of Energy (E) from the sun to the
  earths atmosphere is done by
• Conduction- E transfer by molecular contact
• Convection- E transfer by motion
• Radiation- E transfer via electromagnetic
• transference

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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
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Examples- energy related to phenomena
Sun Sunlight Earths 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
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Solar Radiation The driving factor
Radiation (Electromagnetic

energy) released, absorbed
reflected by all things
travels as both a particle and

a wave
is affected by

-
gravity, magnetism, and

atmosphere composition,
distance, angle of incidence
provides Earth with an

external source of energy


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The electromagnetic spectrum
Wavelength and frequency are inversely related to
one another
Wavelength (1/l) (n) Frequency
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Nature of radiative energy (Radiation) electromag
netic travels as waves and also acts like
particle All things radiate energy a function
of Temperature Stephan-Boltzmans Law F s T
4 Where F is radiation Flux s is a constant 5.67
x 10-8 W/m2K4 T is the temperature in
Kelvin The hotter the object, the more energy it
radiates F (5.67 x 10-8) x (6000)4 73,400,000
W/ m2 (Sun) F (5.67 x 10-8) x (288)4 390 W/
m2 (Earth)
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In general, temperature of emitting body
controls wavelength of outgoing energy hotter
shorter ? cooler longer ? Weins Law allows
us to predict which wavelength will be most
abundant. lmax 2897/T Example Suns surface
temperature is 6000 K lmax 2897/6000
0.48mm Thus, most of suns energy should be at a
wavelength of 0.48 mm
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0.48
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Solar Structure Sun 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 climatology Photospher
e- 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
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Chromosphere A 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 Suns 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 100s of millions of miles away
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Sun spots
Solar Corona
Solar Photosphere
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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
Sun Frec 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
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How much energy does the Earth receive?
Earth---gt
lt---Radius (d)
lt---Sun
Imagine a sphere with a radius (d) the distance
from the Earth to the center of the Sun 1 AU
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Position affects radiation too
Tilted awayless radiation in North
Far awayless radiation


Titled toward more radiation in North
Titled toward more radiation


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Milankovitch Orbital variations Eccentricity -
change of Earths orbit around the Sun from a
Circle to an Ellipse. Timeframe 100,000
years Obliquity- Change in the tilt of the
Earths 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
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Typical albedos of various surfaces to incoming solar 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
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Reflection energy is bounced away without being
absorbed or transformed Scattering energy is
diffused or scattered into different
wavelengths related to composition and thickness
of atmosphere Absorption some gases and aerosols
capture (absorb) energy energy is typically
re-released as longer wavelength radiative
energy Transmissivity The amount of radiation
that actually gets through to the surface
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Greenhouse effect Seen as a bad thing by the
public because of biased (both the left and the
right) or poorly produced media
coverage Greenhouse effect is absolutely
essential to Earths 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 Earths atmosphere
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Energy balance of Earths Surface Energy balance of Earths Surface Energy balance of Earths Surface Energy balance of Earths Surface Energy balance of Earths Surface Energy balance of Earths Surface
Inflow Inflow Inflow Outflow Outflow Outflow
Solar radiation Solar radiation 50 Earth radiation 114 114
Sky radiation Sky radiation 96 Latent Heat 20 20
total total 146 Conduction 12 12
total total 146 total 146 146
Energy balance of Atmosphere Energy balance of Atmosphere Energy balance of Atmosphere Energy balance of Atmosphere Energy balance of Atmosphere Energy balance of Atmosphere
Inflow Inflow Inflow Outflow Outflow Outflow
Solar Radiation Solar Radiation 20 Radiation to space 63 63
Condensation Condensation 20 Radiation to Surface 96 96
Earth Radiation Earth Radiation 107 total 159 159
Conduction Conduction 12 total 159 159
total total 159 total 159 159
Energy Balance of Earth Energy Balance of Earth Energy Balance of Earth Energy Balance of Earth Energy Balance of Earth Energy Balance of Earth
Inflow Inflow Inflow Outflow Outflow Outflow
Solar radiation 100 100 Reflected Radiation Reflected Radiation 30
total 100 100 Sky radiation to space Sky radiation to space 63
Earth radiation to space Earth radiation to space 7
total total 100

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-7
-63
-30
100
Long wave radiation from atmosphere
Incoming solar radiation Solar Constant
Long wave Earth radiation to space
solar radiation reflected and scattered back to
space by atmosphere and surface
solar radiation absorbed by atmosphere
Atmosphere
Long wave Earth radiation
Sensible heat
Latent heat
Long wave sky radiation
Earth
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Distribution of energy
An energy energy budget example