Transcript c-22-section-2-solar-energy-and-the

C. 22 Section 2
Solar Energy and the
Atmosphere
Some of the heat in the
atmosphere comes from:
• The gases absorbing the sun’s rays
• Ocean and land reflection from the solar
energy that was absorbed during the day.
All the energy the Earth receives
from the sun is through:
• Radiation!
• What does radiation include?
• All forms of energy that travel through
space as waves----such as---– Visible light
– Ultraviolet light
– X rays
– Radio waves
Review-all forms of energy of
radiation will travel in waves.
• Light waves are longer than UV, X-ray or radio waves.
• The waves that make up all forms of radiation are called
the electromagnetic spectrum.
• Most energy reaching the Earth is in the form of
electromagnetic waves.
What happens as solar radiation
passes through the atmosphere?
• The upper atmosphere absorbs all
radiation with a wavelength shorter than
visible light.
• Nitrogen and oxygen molecules in the
thermosphere and mesosphere absorb the
X rays, gamma rays and UV rays.
• In the stratosphere UV rays are absorbed
and act upon oxygen molecules to form
ozone (O3).
In the lower atmosphere the waves are absorbed
by CO2, water vapor and other complex molecules
in the troposphere.
Scattering
• This happens when clouds, dust, water
droplets, and gas molecules in the
atmosphere disrupt the paths of the
radiation from the sun.
Scattering occurs when particles and gas
molecules in the atmosphere reflect and bend the
solar rays.
• The deflection causes the rays to travel out in all
directions without changing their wavelengths.
• Some of the wavelengths are sent back out to space and
some continues to Earth.
• The radiation hits Earth from all directions and causes
the sky to appear blue and the sun appear red at sunrise
and sunset.
Reflection
• The Earth’s surface either absorbs or
reflects the energy.
• The absorption or reflection depends on:
color, texture, composition, volume, mass,
transparency, state of matter, and specific
heat of the material.
• How long and the intensity are also factors
for absorption or reflection.
So what is albedo?
• This is the fraction of solar radiation that is
reflected by a particular surface.
• 30% of the solar energy that reaches
Earth’s atmosphere is either reflected or
scattered so Earth is said to have an
albedo of 0.3
Absorption and infrared energy
• Rocks, soil, water, and other surfaces
absorb radiation that is not reflected.
• Absorption of solar radiation, shorter
infrared rays and visible light, they heat
surface materials.
• These waves are converted into longer
waves and are reemitted.
• So what?
This is what heats the lower
atmosphere.
• Therefore, it keeps Earth’s surface much warmer than it
would be if there were no atmosphere.
• Sometimes warm air near the Earth’s surface bends and
causes a mirage.
Review-Greenhouse effect
• Some rays are allowed in and some
cannot get out = heat!
Generally the amount of solar energy that enters
Earth’s atmosphere is about equal to the amount
that escapes to space.
• The problem is that humans may have
changed the balance. Our average
temperatures are rising.
• Carbon dioxide may be to blame—it
intensifies the greenhouse effect.
• It may change the climate on Earth—only
time will tell the truth.
Temperature variations
• Earth is not heated equally.
• It takes time for the absorbed energy to
radiate back out. That is why it is most hot
in the afternoon.
• The temperature of the atmosphere
depends on factors like latitude, surface
features, and the time of year and day.
Latitude and Season
• Earth is a sphere so the sunlight does not
hit all areas at the same angle.
What about water in the air?
• Water vapor will store heat—think of steam and how hot
it can be.
• The high elevations contain less water vapor so it holds
less heat and is cooler in temperature. They become
warm in the day but cool quickly at night.
In what other areas do the
temperatures vary widely?
• Deserts!
•
What about land areas by water?
– Cooler in the day and warmer at night—the water takes a long time to
heat up and then slowly gives off the heat at night.
What about winds?
• Wind from ocean waters are more
moderate in temperature than a similar
region in which the winds blow from the
land.
Conduction and Convection
• Heat transferred by conduction is by
touch.
• Convection causes things to rise and fall
and the movement is up when heated and
down when cooled.
Section 3 Atmospheric Circulation
• Pressure differences cause air movement
everywhere.
• Air generally flows from the poles toward
the equator
You know that the Coriolis effect causes the
air to flow in a curved path.
• Thus winds blowing from high pressure
areas to lower-pressure areas follow a
curved path.