CHAPTER 15EARTH’S

ATMOSPHERE

Section 1

Earth’s atmosphere is a thin layer of air that forms a protective covering around the planet. It protects life forms from some of the Sun’s harmful rays. It keeps Earth’s temperature in a range that can support life.

Earth’s atmosphere is made up of gases, solids and liquids that surround the planet.

Gases in the Atmosphere: Nitrogen is the most abundant gas, making up 78% of the atmosphere. Oxygen actually makes up only 21% of Earth’s atmosphere. Water Vapor makes up as much as 4% of the Earth’s atmosphere. Other gases that make up the atmosphere include argon and carbon dioxide.

Solids and Liquids in the Atmosphere: dust, salt, pollen and liquid droplets other than water droplets in clouds.

LAYERS OF THE ATMOSPHERE

Lower Layers

Troposphere – this is the lowest atmospheric layer. You study, eat, sleep and play in this layer. It contains 99% of the water vapor and 75% of the atmosphere gases. Rain snow and clouds occur in the troposphere, which extends up to about 10km.

Stratosphere – layer above the troposphere that extends from 10km above Earth to about 50km. the stratosphere contains higher levels of a gas called ozone.

Upper Layers

Mesosphere – layer above the stratosphere. If you’ve ever seen a shooting star, you might have witnessed a meteor in the mesosphere.

Thermosphere – named for its high temperatures. This is the thickest atmospheric layer and is found between 85km and 500km above the Earth’s surface.

Exosphere – in contrast to the troposphere, the layer you live in, the exosphere has so few molecules that the wings of the shuttle are useless. In the exosphere, a spacecraft relies on bursts from small rocket thrusters to move around. Beyond the exosphere is outer space.

Within the mesosphere and the thermosphere is a layer of electrically charged particles called the ionosphere.

Atmospheric Pressure: Air pressure is greater near Earth’s surface and decreases higher in the atmosphere.

Temperature in the Atmospheric Layers: (Figure 8/pg.431) the temperature decreases with altitude in the troposphere and mesosphere. The exosphere and thermosphere are closer to the sun therefore temperatures are high. Molecules in the stratosphere absorb some of the sun’s energy and raise the temperature; because ozone molecules are in the upper portion of the stratosphere, the temperature in this layer rises with increasing altitude.

Unspillable Water ExperimentAir pressure can be stronger than gravity. This unspillable water experiment

demonstrates its strength as it keeps the contents of a water glass in place, even upside down.

What You'll Need:Juice glass Water 4x6-inch index card

Step 1: Fill a juice glass full of water. Let the water run over so that the lip of the glass is wet. Be sure that you fill the glass right up to the top.

Step 2: Place a 4x6-inch index card on top of the full glass of water. Be sure to press the card down securely with your hand so that it makes a good seal all around the wet lip of the glass.

Step 3: Working over a sink, hold the card in place with one hand as you turn over the glass. Carefully let go of the index card. The card will stay in place, and the water will stay in the glass.

What happened?

The force of air pressure against the card is stronger than the force of gravity on the water. The air pressure holds the card in place.

The Ozone Layer: atmospheric layer within the stratosphere. Ozone is made up of oxygen. You can’t see it, but your life depends upon it! The ozone absorbs most of the ultraviolet radiation that enters the atmosphere.

Ultraviolet Radiation: one of the many types of energy that come to Earth from the Sun. Can cause skin damage such as cancer.

Chlorofluorocarbons (CFC’s): chemical compounds found in refrigerators, air conditioners, and aerosol sprays that are destroying the ozone layer. If these appliances leak or they are improperly discarded they can enter the Earth’s atmosphere to cause damage.

The Ozone Hole: The destruction of ozone molecules by such things as CFC’s, cause a seasonal reduction in the ozone over Antarctica called the Ozone Hole.

Section 2: Energy Transfer in the Atmosphere

Energy from the sun is reflected back into space by clouds, particles and Earth’s surface and some of the energy is absorbed by the atmosphere.

Heat is energy that flows from an object with a higher temperature to an object with a lower temperature.

Heat is transferred within the Earth’s atmosphere in three

ways:Radiation – energy that is transferred in the form of rays or waves

Conduction – the transfer of energy that occurs when molecules bump into one another

Convection – transfer of heat by the flow of material

- describes all the waters of the Earth

Hydrosphere

The Water Cycle: plays an important role in determining weather patterns and climate

types.

Energy from the sun causes water to change to a gas by a process called evaporation. If water vapor in the atmosphere cools enough this turns into a liquid in a process called condensation. Clouds form when condensation occurs high in the atmosphere. The clouds are made up of tiny water droplets that create precipitation. This completes the cycle in the hydrosphere.

Section 3: Air Movement

Earth is mostly rock or land, with three-fourths of its surface covered by a relatively thin layer of water, the oceans.

These two areas influence the Global Winds

Global Wind

Global wind systems determine the major weather patterns for the entire planet

Global winds were used by early settlers to navigate the oceans.

Sometimes sailors found little to no wind to move their sailing ships near the equator. It also rained nearly every afternoon.

This windless, rainy zone near the equator is called the doldrums.

Coriolis Effect: like the merry-go-round, the rotation of Earth causes moving air and water to appear to turn to the right north of the equator and to the left south of the equator.

Winds in the Upper Troposphere: Jet Streams – narrow belts of strong winds that blow near the top of the troposphere.

Sea and Land Breezes: convection currents over areas where the land

meets the sea can cause wind Sea Breeze:

created during the day because solar radiation warms the land more than the water. These daily winds occur because land heats up and cools off faster than water does.

Land Breeze: movement of air toward the water from the land