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.