Key Concepts 1 Earth’s atmosphere formed as Earth cooled and chemical and biological processes took place. Earth’s atmosphere consists of nitrogen, oxygen, and a small amount of other gases, such as CO 2 and water vapor. The atmospheric layers are the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere. Air pressure decreases as altitude increases. Temperature either increases or decreases as altitude increases, depending on the layer of atmosphere. Lesson 1: Earth’s Atmosphere PhotoLink/Getty Images

Troposphere Troposphere is the layer closest to the Earth’s surface. The Troposphere extends from the Earth’s surface to a height of about 8 – 15 km. Weather develops here Jet stream occurs here Warmest part is near Earth’s surface because sunlight that passes through the atmosphere warms the surface of Earth and then the warmth radiates up Temperature decreases with altitude Air thins with altitude

Stratosphere The stratosphere is the directly above the troposphere. Extends from about 15 km to about 50 km above Earth’s surface. Contains the highest concentration of ozone gas forming a layer called the ozone layer. Unlike the troposphere the stratosphere gets its heat by the ozone layer absorbing radiation from the sun. As a result, it gets warmer the further away you get from the Earth. Weather balloons go as high as the stratosphere. Most planes fly here.

Ozone An Ozone molecule is not the same as a molecule of oxygen gas that you breathe. Ozone absorbs the Sun’s ultraviolet rays more effectively than oxygen molecules therefore protecting Earth from the harmful effects of the ultraviolet rays. Why is the ozone layer becoming thinner? (O ₂ ) Oxygen (O ₃ ) Ozone

Mesosphere The mesosphere extends from the stratosphere to about 85 km above the earth. This is where most meteors burn up upon entry. The coldest place on Earth is at the top of the mesosphere.

Thermosphere The thermosphere is located directly above the mesosphere. The thermosphere can extend to 500 km above the Earth. The air is very thin here and temperatures get extremely hot Hubble Telescope, International Space Station and most Space shuttles orbit in the thermosphere.

Key Concepts 2 Lesson 2:Energy Transfer in the Atmosphere The Sun’s energy is transferred to Earth’s surface and the atmosphere through radiation, conduction, convection, and latent heat. Air circulation patterns are created by convection currents.

Thermal Energy Transfer There are three type of thermal energy transfer that occur between the Sun, atmosphere and Earth. Energy is transferred on Earth and in the atmosphere through: 1: radiation 2: conduction 3: convection Thermal energy always moves from an object with a higher temperature to an object with a lower temperature HIGHER LOWER

Energy on Earth As the Sun’s energy passes through the atmosphere, some of it is absorbed, or taken in, and some of it is reflected back into space. As a result, not all of the energy coming from the Sun reaches Earth’s surface.

Circulating Air in the Atmosphere 1: Solar radiation heats the Earth’s surface 2: The heat from the Earth’s surface is transferred through the atmosphere by conduction. 3: When the layer of air receives enough heat through conduction, it expands, becomes less dense and is pushed upward. Colder, denser air sinks under it. 4: Process is repeated over and over because air is constantly moving and circulating Circulating air affects weather and climate around the world by creating local breezes, winds, cyclones, and thunderstorms.

Key Concepts 3 Uneven heating of Earth’s surface creates pressure differences. Wind is the movement of air from areas of high pressure to areas of low pressure. Air currents curve to the right or to the left due to the Coriolis effect. The main wind belts on Earth are the trade winds, the westerlies, and the polar easterlies. Lesson 3: Air Currents

What are Winds WindWind is the movement of air from areas of high pressure to areas of low pressure. Hot air rises, and cold air sinks creating pressure differences which was created by uneven heating of earths surface. Cool air sinks resulting in HIGH PRESSURE Warm air rises resulting in LOW PRESSURE

Types of Winds: Global Winds Global winds (Prevailing Winds) are really large air masses that are created mainly as a result of the earth’s rotation, the shape of the earth, and the sun’s heating power. Main wind belts in each hemisphere Trade Winds Westerlies Polar Easterlies

Local Winds: Sea Breeze During the day, the land heats up very quickly Air above the land heats up a lot more than air over water Warm, less dense, air over land begins to rise – low pressure is created Colder, denser air over water creates a high pressure system which then moves to occupy empty space over land. Cool air moving from sea to land is called SEA BREEZE A sea breeze is wind that blows from the sea to the land due to local temperature and pressure differences.sea breeze

Local Winds: Land Breeze During the night, the land loses its heat very quickly Water retains its warmth Warm, less dense, air over water begins to rise – low pressure is created Colder, denser air over land creates a high pressure system which then moves to occupy empty space over water. Cool air moving from land to sea is called LAND BREEZE A land breeze is a wind that blows from the land to the sea due to local temperature and pressure differences.land breeze

Key Concepts 4 Some human activities release pollution into the air. Air quality standards are monitored for the health of organisms and to determine if anti-pollution efforts are successful. Lesson 4: Air Quality C. Sherburne/PhotoLink/Getty Images