Thermal Energy Transfer
in the Atmosphere
Temperature and Thermal Energy
TEMPERATURE - a measure of the average kinetic energy of the individual
particles in an object. Thermal Energy – is the total energy of all of the
particles.
Temperature is a measure of…
• The total amount of energy in an object
• The total amount of thermal energy in an object
• How much heat something gives off
• How fast the molecules in an object are moving
Heat is…
• Energy given off or absorbed by an object
• A measure of the motion of the molecules in
an object
• The total amount of molecular energy in an
object
What is Thermal Energy Transfer?
• Thermal energy transfer is the movement of heat energy
from one substance to another.
• Heat (energy) always moves from objects with high
temperature to objects with low
Cold
Hot
What is Thermal Energy Transfer?
Heat will continue to move until both substances are the
same temperature.
Warm
Warm
What is Thermal Energy Transfer?
• The greater the difference in temperature between
the substances, the faster the heat will transfer.
http://www.photoanswers.co.uk/ImgGalleryTn/91/10191/2417_16333.jpg
Your Coke becomes cold because the heat from the soda
transfers into the ice, not the other way around.
No matter what it feels like,
cold does not transfer into
your body.
What is really happening
here?
Why do you wear heavy
clothes when it’s cold
outside?
http://www.alaska-in-pictures.com/data/media/9/man-in-extreme-cold_355.jpg
Examples
• You touch a black car
in the summer and the
heat from the car
transfers into your
hand.
• A breeze makes you
feel cooler because
the wind transfers
heat away from your
body
What is Thermal Energy Transfer?
• There are three types of thermal energy
transfer:
– Radiation
– Conduction
– Convection
Conduction
• The transfer of thermal energy by the collisions
between particles of matter. (through direct
contact).
• Molecules transfer energy to the molecules next
to them.
Conduction
• Conduction – heat
transferred by particles
colliding into one
another, such as in a
metal.
• Transfer of energy by
touch
• Not an effective
transfer in a gas.
• Primarily solids
Conduction
• The molecules do
not have to be the
same substance.
http://www.theelusivefish.com/articles/wp-content/uploads/2007/09/hot-stove.jpg
Transfer of Conduction Energy from
Earth's surface to the atmosphere
• Conduction describes the
transfer of heat (kinetic)
energy between two objects in
physical contact. Soils are
better conductors than water;
water is a better conductor
than air. Therefore, no
significant amount of energy is
transferred by conduction
from Earth's surface to the
atmosphere, only a thin layer
of air touching the ground is
warmed by conduction, which
may however be important for
the local weather/climate.
Thermal energy is CONDUCTED from the
warm ground to the air above it.
Convection
• Heat transfer by convection is the transfer
of thermal energy (heat) through the fluid
(liquids and gases) movement of currents.
Convection
• Convection – heat transferred by the circulation of a
fluid (or gas), such as in a heating system at home;
important near the surface of the Sun.
• Hot air rises cool
air falls
CONVECTION - heat is transferred by the MOVEMENT of currents within a fluid (a
liquid or a gas).
http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap07/FG07_03.jpg
As air above the road warms up, it becomes less dense and
rises and is replaced by
cooler air, forming a convection current.
Convection
• Warm fluids rise, cool down, sink, and
then are warmed again.
Transfer of Convection Energy from
Earth's surface to the atmosphere
•
Convection (also advection) is the
transport of heat as a result of the
movement of water being warmed.
When water is warmed its atoms
move faster and spread apart,
reducing its density, i.e. it will rise.
One could say “Heat rises” but it's
actually the water that is rising. This
creates convection currents and
stands for the remaining 30% of total
heat flux from surface to
atmosphere. Convection (together
with ocean currents) plays a
significant role in transferring heat
pole wards and thereby distributing
heat over the whole Earth. Air mass
advection describes how either cold
or warm air masses travel to areas of
opposite temperature characteristics.
http://www.eeb.ucla.edu/test/faculty/nezlin/Lecture1/Fig0803.jpg
The radiator warms the room by warming the
air around it. Then the warm air transfers heat
to the rest of the room through convection.
When water changes from one phase to another,
Latent heat is exchanged.
Radiation
• There is no direct contact between the
substances.
RADIATION - the transfer of energy by electromagnetic waves. Radiation
does NOT require matter to transfer thermal energy.
Radiation
• Radiation – heat transferred by the flow of
electromagnetic radiation, like heat felt from
the campfire.
• Radiation is the only type of heat transfer
that can happen in a vacuum.
• Heat transfer through
waves
Radiant Energy from the
sun radiates through
empty space to earth.
http://stardate.org/images/gallery/sun5.jpg
http://www.blog.thesietch.org/wp-content/uploads/2007/04/earth.jpg
ENERGY ON EARTH
• Not all of the sun’s energy reaches the Earth’s Surface.
• 20% of the Sun’s Energy is ABSORBED by gases and
particles in the Atmosphere.
• Ozone, Oxygen & Water Vapor absorb ultraviolet light
• Water and carbon dioxide(CO2) absorb infrared light.
• Earth’s Atmosphere (clouds) and the surface of the Earth
REFLECTS about 30% of Sun’s radiation
• About 50% of the Sun’s radiation is absorbed by the
Earth's Surface
RADIATION BALANCE
Earth’s temperature remains stable because of the
balance between the amount of radiation coming from
the Sun and the amount going out from Earth.
Land, trees, and the oceans
absorb and emit solar
radiation mainly in the form of
infrared radiation.
Transfer of Radiation Energy from
Earth's surface to the atmosphere
• Radiation from Earth's surface
to the atmosphere is simply
caused by Earth's temperature
and is equal to 70% of total
heat flux from surface to
atmosphere. This thermal
radiation does not require a
medium, which means that it
can travel through a vacuum
like space. This is for example
how solar energy reaches the
earth, and how heat escapes
from the earth back into
space.
(IR) = Infrared radiation
Energy Heat Transfer - The atmosphere and Earth's surface, including biosphere, geosphere,
hydrosphere and cryosphere, are strongly coupled and exchange, among others, water
vapor and heat through evaporation. These processes are part of the hydrological cycle and
results in condensation, cloud formation, precipitation and runoff, and supply energy to the
weather/climate system. The energy transfer between the earth's surface and the
atmosphere is partly based on infrared radiation, but energy is also transferred by
conduction, convection, and radiation.
THE GREENHOUSE EFFECT
Certain gases, such as
CO2, in the atmosphere
act like the glass in a
greenhouse warming the
atmosphere.
http://www.aos.wisc.edu/~aalopez/aos101/wk5/heatrans.jpg
This picture illustrates all three type of heat transfer.
Can you identify them all?
Conduction
Convection
Radiation
http://www.aos.wisc.edu/~aalopez/aos101/wk5/heatrans.jpg
CLASSWORK
Draw a picture of how energy is transferred from the sun to the earth and then
back to space. Be sure to label Radiation, Conduction and Convection