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Atmosphere structure, Solar Inputs and the Transport of Heat

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Title: Atmosphere structure, Solar Inputs and the Transport of Heat


1
Atmosphere structure, Solar Inputs and the
Transport of Heat
2
Heat, winds, and currents
  • We will address the following topics....
  • Why do the winds blow?
  • The source of the winds is ultimately the Sun.
    Well discuss how heating by the Sun generates
    air flow.
  • What influence does the Earths rotation have on
    winds?
  • Earths rotation causes the winds and currents
    to turnwithout this rotation the climate would
    be very different.
  • Solar Insolation controls almost everything
    But it is not just what we get, it is what we
    keep that defines the thermal balances.

3
Structure of the Modern Atmosphere
  • Pressure force exerted per unit area by the
    weight of overlying air (1 mb 100 Pa 1000 mb
    1bar 1 atm)
  • Temperature measure of the molecular kinetic
    energy.

4
Thermosphere
Thermosphere upper atmospheric layer with
temperature increasing with altitude
  • Heated by absorption of high-energy radiation by
    oxygen
  • Atmosphere is extremely thin, nearly a vacuum. As
    a result, Suns energy can heat air molecules to
    very high temperatures (2500 C) during the day.
    But there are so few, it doesnt really matter

Auroras occur in thermosphere
5
Mesosphere
Mesosphere middle atmospheric layers where
temperature decreases with altitude
  • Temperatures as low as -100 C
  • Million of meteors burn up daily in the
    mesosphere, due to collision with air molecules

Noctilucent clouds (blue-white) over Finland.
6
Stratosphere
Stratosphere temperature increases with altitude
due to absorption of UV by ozone
  • Ozone is concentrated around an altitude of 25 km
    in the ozone layer
  • Ozone layer protects surface from harmful UV
    radiation

7
Troposphere
Troposphere lowest layer in atmosphere,
temperature decreases with altitude
  • Temperature determined by surface heating
  • Well mixed by weather

8
Shortwave radiation
  • Earth receives more solar radiation at low
    latitudes than high latitudes.
  • Ultimately, it is this solar insolation that
    provides the heat that controls weather and
    climate. It is the imbalance across the Earths
    surface that controls winds and currents.

ANNUAL
9
Shortwave radiation
3 factors influence the shortwave radiation
received at Earths surface
  • Beam spreading each unit of shortwave radiation
    is spread over a larger area away from the
    equator

10
Shortwave radiation
3 factors influence the shortwave radiation
received at Earths surface
  • Beam spreading each unit of shortwave radiation
    is spread over a larger area away from the
    equator
  • Beam depletion radiation is absorbed and
    reflected as it passes through atmosphere

11
Shortwave radiation
3 factors influence the shortwave radiation
received at Earths surface
  • Beam spreading each unit of shortwave radiation
    is spread over a larger area away from the
    equator
  • Beam depletion radiation is absorbed and
    reflected as it passes through atmosphere
  • Day length hours of daylight varies with
    latitude and season

12
Shortwave radiation
Earth has seasons because its axis is tilted
23.5º with respect to the plane of the ecliptic
Tilted
No tilt
13
Why do we have seasons?
Seasonal variations in insolation are greatest at
high latitudes
14
Shortwave radiation
Earth receives more solar radiation at low
latitudes than high latitudes
Jun-Jul-Aug
Dec-Jan-Feb.
15
Longwave radiation
Earth emits more longwave radiation at low
latitudes than high latitudes
16
Longwave radiation
Earth emits more longwave radiation at low
latitudes than high latitudes
Jun-Jul-Aug
Dec-Jan-Feb.
Why is there a difference between Winter and
Summer?
17
Net radiation
Net radiation total radiation
  • Net radiation shortwave - longwave
  • There is an energy imbalance!

18
Global Energy Balance
19
Global Energy Balance
20
Global Energy Balance
21
Global Energy Balance
22
Energy Transport
  • To make the energy balance, there must be a
    transport of energy from low to high latitudes.
  • Radiation is converted to other forms of energy
    that can be transported by winds and currents
  • Sensible heat heat that you can feel (stored in
    a substance as a change in temperature)
  • Latent heat heat required to changes phases
    (solid --gt liquid --gt gas)

23
Fluid Flow
Newtons first law A body at rest remains at
rest and a body in motion remains in constant
motion unless acted upon by an external force
  • Fluid flow is driven by forces
  • Forces include
  • Pressure
  • Coriolis
  • Friction

24
Fluid Flow
Pressure force exerted against a surface due to
the weight of air
  • Pressure gradient force fluid flows from high
    pressure to low pressure

25
Fluid Flow
Pressure force exerted against a surface due to
the weight of air
  • Pressure gradient force fluid flows from high
    pressure to low pressure
  • Flow in direction from H to L
  • Larger gradient faster flow

26
Pressure Differences
Pressure differences arise from temperature
differences.
A
B
Heating air causes it to expand In this example,
the masses of the 2 air columns, A and B, are
equal
Equal masses of air
SURFACE
27
Pressure Differences
Pressure differences arise from temperature
differences.
A
B
Top of Atmos.
lt mass
COLD
COLD
gt mass
The mass of air overlying column A is greater
than that overlying column B
SURFACE
28
Pressure Differences
Pressure differences arise from temperature
differences.
A
B
Top of Atmos.
COLD
COLD
Because the mass is greater in column A, the
surface pressure (i.e., the weight of the
overlying air) is greater.
BONUS!
HIGH
LOW
29
Pressure Differences
Pressure differences arise from temperature
differences.
30
General Circulation of the Atmosphere
Circulation on a non-rotating Earth
31
Fluid Flow
Coriolis force an apparent deflection of moving
objects when observed from a rotating reference
frame
Coriolis force is an artificial force that arises
because we are riding on a rotating rock.
32
Fluid Flow
Coriolis force an apparent deflection of moving
objects when observed from a rotating reference
frame
Stationary Observers Perspective
  • Consider two children throwing
  • a ball on a moving merry-go-
  • round.

Rotating Observers Perspective
33
Fluid Flow
Coriolis force an apparent deflection of moving
objects when observed from a rotating reference
frame
Stationary observer
  • The stationary observer sees
  • the ball moving in a straight
  • line, and Johnny and Jill
  • moving in a circle.

34
Fluid Flow
Coriolis force an apparent deflection of moving
objects when observed from a rotating reference
frame
Moving observer
  • Johnny and Jill on the merry-
  • go-round perceive that they are
  • stationary. They see the ball
  • move to the right.

35
Fluid Flow
Coriolis force an apparent deflection of moving
objects when observed from a rotating reference
frame
http//ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/cr
ls.rxml
36
General Circulation of the Atmosphere
Circulation on a rotating Earth
  • Trade winds
  • Mid-latitude westerlies
  • Polar easterlies

37
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38
DESERTS THE CONVERGENCE OF ATMOSPHERIC
CIRCULATION CELLS AND THE SURFACE OF THE EARTH
39
Net radiation
Net radiation total radiation
  • Net radiation shortwave - longwave
  • There is an energy imbalance!
  • Cold Poles and Hot Tropics the drive for
    circulation in both the atmosphere and the ocean
    systems

40
Circulation of the Ocean Thermohaline Driving
Mechanism
41
THE ATLANTIC GULF STREAM WARMING THE POLES
COOLING THE TROPICS
42
MAJOR OCEAN CURRENT SYSTEMS
43
GLOBAL SCALE CIRCULATION OF OCEANS A THERMAL
TRANSFER.
44
SURFACE TEMPERATURE ANOMOLIES
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