The Atmosphere Earth’s atmosphere is a mixture of gases that distributes heat and enables life to exist on Earth

Composition Earth’s Atmosphere is a mixture of gases that distributes heat and enables life to exist on Earth Gases that make up the atmosphere : Keep earth’s surface warm enough to have liquid water Protect against dangerous radiation Prevent Earth’s surface from getting hit by meteors or chunks of rock from space Gases Nitrogen 78% Oxygen 21% Other gases 1% Water vapor <1% Solids Dust, volcanic ash, salt, dirt, smoke Liquids Water

Composition

Atmospheric Pressure & Temperature Air pressure is the measure of the force with which air molecules push on a surface. Air pressure is strongest at the Earth’s surface because more air is above you. As altitude ( distance from sea level) increases, air pressure decreases Air Temperature also changes as altitude increases due to the way solar energy is absorbed as it moves through the atmosphere High % of gases that absorb solar energy= warmer Less gases that absorb solar energy= cooler

Layers of the Atmosphere Thermosphere: temperature increases; does not feel hot; outer most part of atmosphere; no definite outer limit Mesosphere: middle layer; the coldest layer; most meteoroids burn up here, producing meteoroid trails Stratosphere: gases are layered and don’t mix; contains the ozone layer; protects life by absorbing harmful UV radiation Troposphere: layer in which we live; contains almost all of the weather, carbon dioxide, water vapor, clouds, air pollution, and life-forms

Atmospheric Heating

Energy in the Atmosphere Earth and it’s atmosphere are warmed by energy from the sun. We are going to discuss the three ways that this happens: radiation, conduction, and convection

Radiation: Energy Transfer by Waves Radiation is the transfer of energy as electromagnetic waves The earth receives only about 2 Billionths of the energy radiated by the sun, but it’ enough to drive the weather cycle and make life on earth possible

Conduction: Energy Transfer by Contact Thermal Conduction is the transfer of thermal energy through a material by direct contact Thermal energy is always transferred from warm to cold areas When air molecules come into Direct Contact with the warm surface of earth, thermal energy is transferred to the atmosphere.

Convection: Energy Transfer by Circulation convection is the transfer of thermal energy by the circulation or movement of a liquid or gas Most thermal energy in the atmosphere is transferred by convection As air is heated it becomes less dense and rise, Cool air is denser so it sinks, and as the cool air sinks it pushes the warm air up. This cycle of warm air rising and cool air sinking causes a circular movement of air called a convection Current

Greenhouse Effect Greenhouse effect: process in which gases in the atmosphere absorb thermal energy and radiate it back to Earth (water vapor, carbon dioxide) Atmosphere acts as a greenhouse effect because the gases function like the glass walls and roof of a greenhouse. Allowing solar energy to enter but prevents thermal energy from escaping Amount of energy Earth receives everyday from the sun is balanced by the amount of energy Earth radiates back into save (radiation balance)

The Greenhouse Effect

Greenhouse Gases and Global Warming Global Warming is the gradual increase in average global temperature Human activity, such as burning of fossil fuels, and deforestation, may be increasing the levels of greenhouse gases, such as carbon dioxide, in the atmosphere If global warming temperatures continue to rise, it could disrupt global climate patterns

Quick Check Why does the temperature of different layers of the atmosphere vary?   a. because air temperature increases as altitude increases b. because the amount of energy radiated from the sun varies c. because of interference by humans d. because of the composition of gases in each layer

Quick Check What is the most abundant gas in the atmosphere? a. oxygen b. hydrogen c. nitrogen d. carbon dioxide

Quick Check A major source of oxygen for the earth’s atmosphere is a. sea water. b. the sun. c. animals d. plants

Quick Check The bottom layer of the atmosphere where almost all weather occurs, is the a. stratosphere b. troposphere c. thermosphere d. mesosphere

Quick Check The ozone layer is located in the a. stratosphere b. troposphere c. thermosphere d. mesosphere

Quick Check Match the correct definition with the correct term. a. troposphere b. thermosphere c. stratosphere d. mesosphere ______ contains the ozone layer, which protects us from harmful radiation ______ the coldest atmospheric layer; Meteoroids burn up in this layer ______ is the lowest atmospheric layer; it is the layer in which we live. ______ the uppermost layer of the atmosphere.

Quick Check What percentage of the solar energy that reaches the outer atmosphere is absorbed at the Earth’s surface? a. 20% b. 30% c. 50% d. 70%

Quick Check Which of the following is the best example of thermal conduction? a. A light bulb warming a lampshade b. An egg cooking in a frying pan c. Sitting by a fireplace getting warm by the fire d. Gases circulating in the atmosphere

Quick Check By which method does most thermal energy in the atmosphere circulate? a. conduction b. convection c. advection d. radiation

Quick Check The balance between incoming and outgoing energy is called a. The convection balance. b. The conduction balance. c. The greenhouse effect. d. The radiation balance.

Quick Check As the sun heats the surface of the ocean, some of the water evaporates and enters the air. How does water vapor move in the atmosphere? a. by waves b. by clouds c. by conduction d. by convection

Quick Check Energy transferred as electromagnetic waves is called a. thermal conduction. b. convection. c. radiation. d. convection current.

Quick Check The process by which gases in the atmosphere absorb thermal energy and radiate it back to earth is called a. the thermal effect. b. global warming c. the greenhouse effect. d. radiation balance.