Heating the Earth

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Transcript Heating the Earth

Heating the Earth
Air Pressure
Energy From the Sun
Where We Get Our Energy
• The Sun is a major source of energy
for Earth.
• You can feel the radiant energy warming
your skin
• Radiation- movement of energy through
empty space
Sun’s Energy
Absorption of Energy
• Dark surfaces absorb light, and it is
usually changed into heat
• Surfaces that reflect light, such as
white, remain cooler
• The troposphere is heated by moving
heat through matter
• How does heat move through a metal
• Conduction- heat moves from an area of
higher temperature to area of lower
• Radiant energy travels from the Sun
through space in waves
• Radiation passes easily through the
atmosphere to the surface
• Surface radiates most back into
• Transfer of heat within a liquid or gas
• As air heats it expands, becomes lighter
• Warm air becomes lighter than cool air,
so warm air rises
• Cooler, denser air sinks
Forms of Energy
• Let’s look at this animation for
radiation, conduction, and convection
• http://www.wisconline.com/Objects/ViewObject.aspx?I
What is Air Pressure?
• Pressure- the amount of force per unit
of area
• Weight- weight (force) is measured in
• Ex.- Holding a book (pg. 260)
• Force over small area causes more
pressure than a large area
Air Pressure in Atmosphere
• Air molecules are in constant motion and
pulled toward Earth’s center by gravity
• Force of all the molecules moving causes
air pressure
• Air pressure is greatest near surface
• What happens to air pressure as
elevation changes?
• Air pressure decreases as distance
above surface increases
• Very little weight of air pressing down
Water Vapor
• Water evaporates from lakes, rivers,
and oceans
• Water vapor molecules are lighter than
other gas molecules
• So, more water vapor in air, the lower
the air pressure
Measuring Air Pressure
• Barometer- air pressure is measured
with this instrument
• Air pressure pushes down on the
surface of the mercury in the
• Standard air pressure- 760 mm of
mercury or 1 atmosphere or 1,013.20 mb
How do Winds Form?
• Wind- the horizontal movement of air
along Earth’s surface
• Earth’s atmosphere is always in motion
• Winds form as cool, heavy air moves
toward warm, light air
• Cool air moves along the surface toward
warmer air
How do Winds form?
• Winds are also caused by differences in
air pressure
• Cold, heavy air have high air pressure
• Warm, light air have low air pressure
• Speed of wind depends on the
differences in air pressure
Air Currents
• Air currents- up-and-down movements
of air
• Some areas of Earth are warmed more
than others
• Warmer air expands, becomes less
• Figure 11-21 pg. 266