The Earth’s AtmosphereThe Earth’s Atmosphere

6.66.6 The student will investigate and The student will investigate and understand the properties of air and the understand the properties of air and the structure and dynamics of the Earth’s structure and dynamics of the Earth’s atmosphere. atmosphere.

SOL 6.6aSOL 6.6aAir is a mixture of gaseous elements Air is a mixture of gaseous elements and compounds. and compounds.

• The atmosphere is a mixture of many gases, dust and more additional materials than you can imagine.

Elements • Approximately 78% of the air is nitrogen. (N2)• Approximately 21% of the air is oxygen. (O2)• Argon and other gases make up about 1%

Argon and other gases make up Argon and other gases make up the remaining 1% of our air.the remaining 1% of our air.

• Argon 0.93 %

• Carbon Dioxide 0.036 %

• Neon 0.0018 %

• Helium 0.00052 %

• Methane 0.00015 %

• Krypton 0.00011 %

• Hydrogen 0.00005 %

Air contains gaseous Air contains gaseous compoundscompounds..

• Carbon and oxygen combine to form CO2

• Nitrogen and oxygen form nitrogen dioxide NO2

• Hydrogen and oxygen combine to form H2O ( water vapor ).

Nitrogen78%

Oxygen 21%

Argon and other gases 1%

Air contains many other ingredients!Air contains many other ingredients!

• Millions of tons of particles and polluting gases…• Particles from volcanoes• Salt grains from ocean spray• Dust from meteors• Sand from desert storms• Soot from fires• Rubber vaporized from car tires• Pollen from plants, bacteria, spores from fungi• Chemicals from fertilizers and pesticides• Dust and other human wastes• Carbon monoxide (CO) Emissions from vehicles

Photochemical Photochemical SmogSmog

• Smog is a thick, brownish haze formed when certain gases in the air react with sunlight.

• Major sources of smog are the gases emitted by automobiles and trucks.

• These gases, (hydrocarbons and nitrogen oxides, react in the sunlight, forming ozone (O3). The major, toxic chemical found in Smog.

Acid rainAcid rain

• Another type of pollution caused by power plants and factories, that burn coal and oil

• These fuels produce nitrogen oxides and sulfur oxides when burned.

• Nitric acid and sulfuric acid are created when these gases react with water vapor.

• These acids return to Earth, dissolved in precipitation, as acid rain. (ph may be 4.0)

Properties of AirProperties of Air

• Air has mass – air is made up of atoms, and molecules.

• Air has volume - takes up space.

• Air has density – mass/volume

• Air has pressure – the weight of a column of air pushing down on a surface or area

Air PressureAir Pressure

• Air pressure is measured with a barometer. The barometer may be a mercury barometer or an aneroid barometer.

Altitude and air pressureAltitude and air pressure

• Air pressure decreases with altitude – there is less air pressure on the top of a mountain that at sea level.

• The density of air also decreases with altitude. (More difficult to breathe at high altitudes)

Layers of the AtmosphereLayers of the Atmosphere

The four main layers of the atmosphere are classified according to changes in temperature.

These layers are the Troposphere, the Stratosphere, the Mesosphere, and the Thermosphere.

TroposphereTroposphere

• The layer of the atmosphere closest to the Earth’s surface

• We live in the troposphere• Nearly all of the Earth’s weather occurs in this

layer• Contains 80 % of the atmosphere’s mass• Contains 99 % of the atmosphere’s water• Tropopause separates this layer from the

stratosphere

Troposphere continuedTroposphere continued

• The height of the troposphere varies from 16km to 19km above the equator and 9km to 10km above the North and South poles.

• The temperature at the bottom of this layer (The Earth’s surface) averages 15° Celsius (59° Fahrenheit)

• As the altitude increases in the troposphere the temperature decreases. On average each 1km increase in altitude results in a temperature drop of 6.5° Celsius, until it remains constant at about -60° Celsius.

• Water at the top of the troposphere forms thin, feathery, clouds of ice.

• The Tropopause separates this layer from the stratosphere

The Troposphere affects our The Troposphere affects our weather.weather.

• Temperature variations within this layer help create our weather.

• Colder, denser air sinks, forcing warmer, less dense air to rise. Rising air expands and cools. Water vapor may condense and form clouds and possibly precipitation.

• Sinking air is compressed and warms. In this warmer air, clouds may vaporize or fail to form, resulting in fair weather.

StratosphereStratosphere

• The stratosphere begins at the top of the troposphere.

• The stratosphere begins at about 10km (6 miles) above the Earth’s surface at the poles.

• The stratosphere begins at about 19km (12 miles) above the Earth’s surface at the Equator.

• The upper boundary, the stratopause, reaches up to about 48km to 50km (30 miles).

Stratosphere continued,Stratosphere continued,

• The temperature in the lower level is steady at approximately - 55° Celsius to -60° Celsius (- 167° Fahrenheit).

• The upper layer is warmer, reaching approximately -2° Celsius (28° Fahrenheit)

• Ozone in this upper region, absorbs harmful, ultraviolet radiation from the sun.

Ozone in the stratosphereOzone in the stratosphere

• Ozone (O3) absorbs this light and converts it into heat. This is why the upper region of this layer is warmer.

• About 80 to 90% of the ozone in the atmosphere is found in the stratosphere.

Ozone data: Ozone data: compliments of a sixth compliments of a sixth

grade studentgrade student

• Ozone can aggravate asthma

• Ozone can cause reduced lung function, inflame chronic lung disease and cause permanent damage to lungs

• Prevention of exposure includes reducing outdoor activities

Stratosphere and weatherStratosphere and weather

• Strong, complex winds, known as the jet stream are located in the boundaries between the stratosphere and the troposphere.

Stratosphere and weatherStratosphere and weather

• The stratosphere is extremely dry, nearly cloudless, and weather does not occur there. Ice clouds however, do form above the polar regions in the winter time.

Stratosphere and weatherStratosphere and weather

• Weather balloons rise into the stratosphere before they burst, allowing their instrument packages to fall back to Earth.

Mesosphere LocationMesosphere Location

• The mesosphere begins at an altitude of about 48 to 50 km (30 miles) above the Earth’s surface, and extends to about 80 km (50 miles), upward.

Mesosphere temperaturesMesosphere temperatures

• A drop in temperature above the stratosphere, marks the beginning of the mesosphere.

• Temperatures decrease as you go higher in the mesosphere, reaching -90° to -109° Celsius (-165° Fahrenheit).

MesosphereMesosphere

• The mesosphere protects the Earth from meteorites, chunks of rock and metal from space, as they usually burn up upon entering this layer.

• “Shooting stars,” or meteors, leave a trail of burning gases that are often seen in this part of the atmosphere.

ThermosphereThermosphere

• The thermosphere begins at the mesopause, the uppermost boundary of the mesosphere at about 80 km (50 miles) and continues into space

• It has no definite outer edge. Gas atoms and molecules there are so far apart that the air blends gradually with outer space, (1000+ kilometers or 620+ miles, above the Earth).

Thermosphere ContinuedThermosphere Continued

• The air at the upper boundary of the mesosphere is very thin. Imagine one cubic meter of air at sea level, being expanded to 100,000 cubic meters at the mesopause.

• The air in the thermosphere is even thinner.

Thermosphere CompositionThermosphere Composition

• Molecules of nitrogen (N2) and atoms of Oxygen (O) make up most of the lower parts.

• At about 200km (125 miles) Oxygen atoms begin to outnumber nitrogen molecules.

• Above 1000Km (620 miles) the thermosphere contains mainly Hydrogen and Helium.

Thermosphere TemperatureThermosphere Temperature

• The thermo in thermosphere means “heat.”

• Air temperatures rise steadily with altitude.

• The temperature rises from about -90°C

(-130°F) at an altitude of 80 Km, to more than 1200°C (2200°F) at about 350Km (220 miles).

Thermosphere absorbs heatThermosphere absorbs heat

• The upper region of the thermosphere, the exosphere, absorbs more radiation from the sun.

• Changes in solar activity cause the temperatures in the thermosphere to vary more than any other layer.

Heat is not transferredHeat is not transferred

• High temperatures result from rapid movement of the atoms and molecules.

• Because the atoms and molecules are spaced so far apart, their movement is not recorded on ordinary thermometers. (Temperature would appear to be well below 0° Celsius).

When is 2200° Fahrenheit cool?When is 2200° Fahrenheit cool?

• You would not feel warm in the thermosphere.

• Satellites and other spacecraft also stay cool in this layer because the air is too thin to transfer much heat.

Thermosphere divided in two…Thermosphere divided in two…

• The thermosphere is divided into two parts

• The lower layer, the Ionsphere, begins at about 80 Km above the Earth’s surface, and continues up to about 550 Km.

• Energy from the sun causes gas molecules to be come electrically charged particles called Ions.

IonosphereIonosphere

• Radio waves bounce of the ions and then bounce back to the Earth’s surface, allowing us to communicate.

IonosphereIonosphere

• The Northern Lights, (aurora borealis) also occur in the Ionosphere.

• Particles from the sun enter the ionosphere near the North Pole, striking Oxygen and Nitrogen atoms, causing them to glow.

ExosphereExosphere

• Exo- means “outer,” so the exosphere is the outer layer of the Thermosphere.

• The exosphere extends from about 550 km above the Earth’s surface, outward for 1000’s of km to outer space.

Satellites in the ExosphereSatellites in the Exosphere

• Satellites traveling in the exosphere are used for transmitting signals used for cell phones, television, tracking the weather and carrying telescopes to look into space.