physical science 22 characteristics of the atmosphere

Physical Science 22Characteristics of the

Atmosphere

Objectives

• Identify the primary layers of the atmosphere

• Describe how the atmosphere has evolved over time

• Describe how the oxygen-carbon dioxide cycle works, and explain its importance to living organisms

• Discuss the recent changes in Earth’s atmosphere

Layers of the atmosphere

• Earth’s atmosphere consists of two main gases:

• Nitrogen 78%

• Oxygen 21%

• Trace elements~ 1%

The atmosphere has several different layers

• The layers differ in:

temperature

density

amount of gases present

• Turn to page 742 in your text book

• Copy figure 1 in your notebook

Be sure to note the different atmosphere layers, location, temperature, altitude, pressure, and special characteristics

Almost all weather occurs in the troposphere

• Troposphere-the lowest layer of the atmosphere, in which temperature drops at a constant rate as altitude increases

• This is the densest of the layers due to the weight of all other layers

The troposphere gets cooler with increasing altitude

• At the top of the troposphere the temperature stops decreasing

• This region, the tropopause, at (-55°C) keeps the water vapor and clouds.

Cold air can be trapped beneath warm air

• Temperature inversion- the atmospheric condition in which warm air traps cooler air near Earth’s surface

• This occurrence can trap pollution in areas surrounded by mountains

Stratosphere

• Stratosphere- the upper layer of the atmosphere, which lies immediately above the troposphere and extends from 10 km to about 50 km above Earth’s surface

• Ozone-a gas molecule that is made up of three oxygen atoms

• The stratosphere is a cold, low-pressure layer

• Key differences:– Little water vapor– No weather or clouds– Increase in temperature with increased

altitude (ozone layer-absorbs much of the sun’s ultraviolet radiation)

The mesosphere and thermosphere exhibit extremes of

temperature• Mesosphere- the coldest layer of the

atmosphere, between the stratosphere and the mesosphere (-80°C °F? )

• Thermosphere- the upper-most layer of the atmosphere, in which temperature increases as altitude increases

(980°C °F? )

Ionosphere is used in radio communication

• Ionosphere- area in which solar energy is absorbed in the lower thermosphere and upper mesosphere

(creating electrically charged ions)

• Electrons in the ionosphere reflect radio waves, allowing them to be received over long distances

Auroras

• Auroras- colorful light displays in the ionosphere that encircle Earth’s magnetic poles

• Form when energetic ions from the sun hit atoms and molecules causing photons of light to be emitted– Aurora borealis– Aurora australis

Changing in Earth’s Atmosphere

• Early in Earth’s existence, the atmosphere contained mostly carbon dioxide, nitrogen, and a few other trace gases

( H2, water vapor, H20, NH3, CH4, CO, CO2, but no O2)

This was due to outgassing from volcanoes

Photosynthetic plants contribute oxygen to the atmosphere

• Around 2.5 billion years some cells evolved a method of capturing energy from the sun and converting it to sugar that can be used as a food source

• Photosynthesis produces oxygen as a byproduct

Animals produce carbon dioxide necessary for photosynthesis

• In the oxygen-carbon dioxide cycle, plants produce oxygen, which is used by animals for respiration

• Animals produce carbon dioxide, which is used by plants for photosynthesis

Man-made chemicals can deplete the ozone layer

• Remember the ozone layer is in the stratosphere!!!

• O3 molecules absorb much of the sun’s damaging ultraviolet radiation

• Without the ozone layer UV rays would cause serious cellular damage

Ozone destruction

• Ozone destruction is caused by chlorofluorocarbons (CFCs)

• CFCs were widely used as refrigerants and in aerosol spray cans

• CFC use was banned Jan 1st 1996

The greenhouse effect keeps Earth warm

• Greenhouse effect- the warming of the surface and lower atmosphere of Earth that occurs when carbon dioxide, water vapor, and other gases in the air absorb and reradiate infrared radiation

• The greenhouse effect is a process in which atmospheric gases trap some of the energy from the sun in the troposphere

• A. Solar radiation warms Earth’s surface and is radiated back into the atmosphere as heat radiation

• B. Greenhouse gases, CO2 and H2O receive this heat radiation and radiate some back to Earth’s surface

• C. CO2 is added to the air in the burning of fossil fuels and in forest fires, possibly causing global warming!

Increased levels of carbon dioxide may lead to global warming

• Without the greenhouse effect, Earth would have a colder average temperature

• If too much heat is trapped, the global temperature will rise

• Global warming could cause the icecaps to melt, ocean levels to rise, and droughts to occur in some areas!

Sources of carbon dioxide

• Burning of coal, oil, and gas for power plants, machinery, and cars

Cause of global warming and what to do about it is highly debatable

Assignment

• Work on Earth Science Review Packet