Earth’s Atmosphere Chapter 1---Section 1

Atmosphere Thin layer of air that forms a protective covering around the planet Mixture of gases, solids, and liquids Extends from surface to outer space Much different today than from when it was young

Protective Covering… Keeps Earth’s temperature in a range that can support life Protects life-forms from harmful ultraviolet rays Reduces most meteors to dust and gas before they hit Earth’s surface

Early Atmosphere Produced by erupting volcanoes Contained nitrogen and carbon dioxide, but little oxygen About 2 million years ago, early photosynthetic organisms started to create oxygen.

Composition of the Atmosphere Gases Nitrogen (78%) Oxygen (21%) Water Vapor (0-4%) Argon Carbon dioxide Other trace gases Solids Dust Pollen Liquids From erupting volcanoes Condensed water vapor in clouds

Humans are causing the composition of the atmosphere to change Car exhaust contains gases which combine with oxygen in the presence of sunlight to create smog (brown haze) Carbon dioxide is increasing due to the burning of fossil fuels. This is leading to an increase in global temperature known as the Greenhouse Effect.

Layers of the Atmosphere Troposphere Lowest layer (extends up to 10 km) Contains 99% of water vapor and 75% of atmospheric gases Where weather occurs Temperature decreases with altitude (because it gets its heat from Earth’s surface) Stratosphere directly above the troposphere (extends up to 50 km) Contains the “ozone layer” Temp. increases with alt. (because the ozone traps sun’s rays)

Mesosphere Thermosphere Exosphere Directly above stratosphere (extends up to 85 km) Where meteors burn up (shooting stars) Temp. decreases with alt. Thermosphere Directly above mesosphere (extends up to 500 km) Thickest layer Aurora borealis occurs here Temp. increases with alt. (molecules are first to receive sun’s rays) Exosphere Outermost layer (dissipates into space) Space shuttle/satellites orbit here Temp. increases with alt.

Ionosphere Layer of electrically charged particles within the mesosphere and thermosphere Absorbs AM radio waves during the day and reflects them back at night

Atmospheric Pressure Force exerted on an area by the weight of overlying air Greatest near Earth’s surface and decreases with altitude Why? Because the mass of the gases higher up in the atmosphere are pushing down on the gases closer towards the Earth’s surface

Ozone Layer Found within the stratosphere (19 km - 48 km) Ozone is made up of three oxygen atoms. It is different from the oxygen we breathe, which only has two oxygen atoms. Absorbs most UV radiation that enters the atmosphere Too much exposure can cause skin cancer as well as damage other life-forms

Chlorofluorocarbons (CFCs) are destroying the ozone layer Come from refrigerators, ACs, aerosol sprays, and the production of some foam packaging Enter the atmosphere through leaks and when things containing CFCs are disposed of improperly One chlorine atom from a CFC molecule can destroy approximately 100,000 ozone molecules!

The destruction of ozone molecules seems to cause a seasonal reduction in ozone over Antarctica called the ozone hole. Starts to decrease in late Aug/early Sep and reaches its lowest values in Oct. By Dec, the ozone hole is gone. In the mid-1990s, some governments banned the production and use of CFCs. Since then, their concentration in the atmosphere has started to decrease.

Energy From the Sun Chapter 1------Section 2

Energy from the Sun The Sun provides most of Earth’s energy This energy drives wind, ocean currents, and allows plants to grow, producing oxygen and food for animals

Radiation from the Sun can be: Reflected into space (35%) Absorbed by the atmosphere Absorbed by land or water Energy reaches Earth’s surface and heats it Heat - energy that flows from an object with a higher temp to an object with a lower temp

Heat is transferred through the atmosphere in three ways: Radiation Conduction Convection

Radiation Energy that is transferred in the form of rays or waves Energy from the Sun reaches the Earth in the form of radiant energy. Earth radiates some of the energy it absorbs back into space. Radiant energy from the Sun warms your face.

Conduction The transfer of energy that occurs when molecules bump into one another Molecules in warm objects move faster than molecules in cooler objects. When objects are in contact, energy is transferred from warmer objects to cooler objects. As air moves over warm land or water, molecules in the air are heated by conduction (direct contact with the ground).

Convection The transfer of heat by the flow of material Convection circulates heat throughout the atmosphere. Convection Currents form when cooler, denser air sinks while warmer, less dense air rises.

The Water Cycle The constant cycling of water within the atmosphere and hydrosphere Hydrosphere - a term that describes all of Earth’s waters Plays an important role in determining weather patterns and climate types

Evaporation- Energy from the Sun causes water to change from a liquid to a gas by this process. Condensation- when water vapor in the atmosphere cools and changes back into a liquid.

Why doesn’t life exist on Mars or Venus? Mars is a cold, lifeless world because its atmosphere is too thin to support life or to hold much of the Sun’s heat. Gases in Venus’ dense atmosphere trap heat coming from the Sun making it way too hot to support life. Living things would burn instantly if placed on Venus’ surface. Avg. temp. 470 ˚C (hot enough to melt lead!) Life on Earth exists because the atmosphere holds in just the right amount of the Sun’s energy.

Air Movement Chapter 1----Section 3

Wind The movement of air from an area of higher pressure to an area of lower pressure Caused by the uneven heating of Earth’s surface: Land and water heat up/cool down at different rates Angle of incidence of Sun’s rays affects how much thermal energy different parts of the world receive

Always named for the direction from which they blow Ex: An easterly wind blows from the east toward the west.

Coriolis Effect Causes moving air to turn to the right in the northern hemisphere and to the left in the southern hemisphere Caused by Earth’s rotation

Angle of Incidence Each square meter of area at the equator receives more energy from the Sun than each square meter at the poles does. Due to the angle at which sunlight strikes the atmosphere at the poles, it has to travel through a thicker layer of atmosphere meaning it has a greater chance of getting absorbed, scattered, or reflected before reaching Earth’s surface.

Global Winds Distinct wind patterns on Earth’s surface are caused by: differences in the amount of incoming solar radiation (insolation). the Coriolis effect. The Sun’s uneven heating of the Earth’s surface forms giant loops, or cells, of moving air. The Coriolis effect deflects the surface winds to the west or east, setting up belts of prevailing winds that distribute heat and moisture around the globe.

Doldrums A windless, rainy zone near the equator. Near the equator, Sun heats the air, causes it to rise, creating low pressure and little wind The rising air cools, causing rain

Wind Belts Trade Winds - Blow from the subtropical highs to the low pressure belt at the equator (easterly) Prevailing Westerlies - Blow from the subtropical high to the subpolar lows (from west to east) Polar Easterlies - Blow from the polar highs to the subpolar lows (from east to west)

Jet Streams Narrow belts of strong winds that blow near the top of the troposphere The polar jet stream forms at the boundary of cold, dry polar air to the north and warmer, moist air to the south. Moves faster in the winter because the difference between cold air and warm air is greater Helps storms move across the country Flows from west to east

Sea & Land Breezes Caused by convection currents over areas where the land meets the sea Sea Breeze Wind blowing from sea to land Forms during the day Cooler, denser air over water has a higher pressure and flows toward the warm, less dense air over the land

Land Breeze Winds blowing from land to sea Forms during the night Cooler, denser air over land has a higher pressure and flows toward the warm, less dense air over the water