Transcript Key Idea #14

Key Idea #14
There is a
relationship between
the warming of the
Earth’s atmosphere
by the sun and
convection within the
atmosphere and
oceans.
http://hurricanetrack.com/jpegs/ingred1.jpg
Energy from the Sun
Nuclear reactions that take
place in the sun produce
heat and light.
The sun is the main source
of Earth’s energy, and also
the major cause of heat in
our atmosphere.
Most of the energy that
heats up Earth’s
atmosphere is from
infrared radiation.
The heating of the Earth
at any location is related
to the angle of the sun
in the sky.
Only a small percentage
of light energy from the
sun that hits the Earth
produces heat energy on
Earth.
Seasons FYI
The hemisphere that is
tilted toward the sun
receives more direct
sunlight and experiences
spring and summer.
The hemisphere that is
tilted away from the sun
is receiving less direct
light and experiences fall
and winter.
The sun’s rays are least
direct at the north and
south poles.
http://web.srv.cmes.utah.edu:8080/west/k12/EarthsTiltPic/view
Light energy from the sun is absorbed by the Earth’s surface and
changed into heat energy. The heat energy radiates out and heats
the air above.
http://www.physorg.com/news96641929.html
Carbon dioxide
and water vapor
in the air absorb
this heat energy
and radiate
some of it back
to the Earth’s
surface, making
the Earth warm
enough to
support life.
http://assets.panda.org/img/original/faq_1_3_fig_1.jpg
The Greenhouse Effect
Gases in the atmosphere that hold heat
are called greenhouse gases.
The greenhouse effect is the process by
which these gases hold heat in the
atmosphere.
Greenhouse gases include water vapor,
carbon dioxide, and methane.
Global Warming
Human activities including the burning
of fossil fuels such as wood, coal, oil,
and natural gas add carbon dioxide to
the air.
If increased carbon dioxide traps more
heat, the temperature of Earth’s
atmosphere increases resulting in global
warming.
The Greenhouse Effect
and Global Warming
Heat refers to the energy transferred
from a hotter object to a cooler one.
Heat is transferred in three ways:
radiation
conduction
convection
Radiation, conduction, and convection in a
lava lamp.
Radiation
The light bulb on a lava lamp heats coil.
Conduction
The heated coil touches “lava” causing molecules to
speed up and spread out.
Convection
The warm lava rises because it is less dense
(D=M/V).
The “lava” that is further from the energy source
cools causing molecules to move closer together.
The cooled “lava” sinks because it is more dense.
Radiation, conduction, and convection work
together to heat the troposphere.
Radiation:
The direct transfer of energy
from the sun by electromagnetic
waves and is felt as heat.
Conduction
The direct transfer of heat energy
caused by contact between one
object and another (example:
your feet on hot sand).
Convection
The transfer of heat energy
through fluids (liquids and gases)
by moving particles.
http://www.kudzuacres.com/wwow/lessons/weather/radiationconduction.gif
Convection currents move warm air through the
atmosphere.
Convection takes
place because cold air
is more dense than
warm air.
Cold, dense air sinks
which forces the
warm, less dense air
to rise.
Convection currents
causes most of the
heating of the
troposphere.
http://www.propertiesofmatter.si.edu/images/L5/conv_cell_atmos_labeled.gif
The Sun and Weather