Characteristics of the Characteristics of the AtmosphereAtmosphere

77thth Grade Science Grade ScienceMr. BombickMr. Bombick

OutlineOutline1.Composition2.Properties3.Organization4.Involvement with Biosphere5.Pollutants

Composition of Dry AirComposition of Dry AirAir ComponentAir Component % of Dry Air% of Dry Air

NitrogenNitrogen 7878

OxygenOxygen 2121

Other (COOther (CO22, H, H22O, O, Noble Gases, HNoble Gases, H22, ,

Methane, Methane, ParticulatesParticulates

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Components of AirComponents of Air

Nitrogen-Each nitrogen molecule contains Nitrogen-Each nitrogen molecule contains two nitrogen atoms; usually biologically inerttwo nitrogen atoms; usually biologically inert

Oxygen-Most oxygen molecules contain two Oxygen-Most oxygen molecules contain two oxygen atoms; critical for animal life; oxygen atoms; critical for animal life; involved in combustion processes; ozone is involved in combustion processes; ozone is a harmful oxygen molecule that contains a harmful oxygen molecule that contains three oxygen atoms (generated by lightning three oxygen atoms (generated by lightning and human sources)and human sources)

Components of Air (cont.)Components of Air (cont.) Carbon Dioxide-Each molecule of carbon Carbon Dioxide-Each molecule of carbon

dioxide has one atom of carbon and two dioxide has one atom of carbon and two atoms of oxygen; absorbed by plant atoms of oxygen; absorbed by plant photosynthesis; released by human sourcesphotosynthesis; released by human sources

Water Vapor-Each water molecule contains Water Vapor-Each water molecule contains one oxygen atom and two hydrogen atoms; one oxygen atom and two hydrogen atoms; wide variations in amount of water vapor wide variations in amount of water vapor depending on the type of climate; critical to depending on the type of climate; critical to formation of clouds; basis of precipitationformation of clouds; basis of precipitation

Components of Air (cont.)Components of Air (cont.)

Other Gases-Hydrogen (one molecule Other Gases-Hydrogen (one molecule of hydrogen contains two atoms of of hydrogen contains two atoms of hydrogen); Noble gases (argon, neon, hydrogen); Noble gases (argon, neon, krypton); methane released from krypton); methane released from biological and human sourcesbiological and human sources

Particulates-solid particles from Particulates-solid particles from biological and chemical sourcesbiological and chemical sources

Properties of the Properties of the AtmosphereAtmosphere

Density-measurement of the Density-measurement of the amount of mass in a given amount of mass in a given volume of airvolume of air

Pressure-The amount of force Pressure-The amount of force of air due to weight of a column of air due to weight of a column of air pushing down on an areaof air pushing down on an area

Measurement of Air Measurement of Air PressurePressure

Can be measured using a barometer (can be Can be measured using a barometer (can be a mercury or aneroid barometer)a mercury or aneroid barometer)

Units of air pressure are given as “inches of Units of air pressure are given as “inches of mercury” or in millibars (National Weather mercury” or in millibars (National Weather Service uses millibars)Service uses millibars)

Inches of mercury refers to the height of a Inches of mercury refers to the height of a mercury column caused by air pressuremercury column caused by air pressure

Millibars are related to inches to mercury Millibars are related to inches to mercury (one inch of mercury equals 33.87 millibars(one inch of mercury equals 33.87 millibars

Air Pressure and Air Pressure and AltitudeAltitude

Air pressure decreases with Air pressure decreases with increasing altitudeincreasing altitude

Air pressure is greatest at sea Air pressure is greatest at sea levellevel

For air pressure to exist there has For air pressure to exist there has to be airto be air

Air Pressure and Air Pressure and DensityDensity

Increasing altitude results in Increasing altitude results in lower air densitylower air density

Gas molecules get farther Gas molecules get farther apart with increasing altitude apart with increasing altitude (due to less pressure)(due to less pressure)

Layers of the Layers of the AtmosphereAtmosphere

Troposphere (0 to 12 km)Troposphere (0 to 12 km) Stratosphere (12 to 50 km)Stratosphere (12 to 50 km) Mesosphere (50 to 80 km)Mesosphere (50 to 80 km) Thermosphere (Above 80 km) Thermosphere (Above 80 km)

composed of Ionosphere and composed of Ionosphere and ExosphereExosphere

TroposphereTroposphere Closest layer to the earthClosest layer to the earth Conditions of this layer are the most Conditions of this layer are the most

variablevariable Layer where weather occursLayer where weather occurs Contains almost all the mass of the Contains almost all the mass of the

atmosphereatmosphere This layer is thickest above the This layer is thickest above the

equator and thinnest at the polesequator and thinnest at the poles

StratosphereStratosphere Extends from top of troposphere to Extends from top of troposphere to

approximately 50 km above Earth’s approximately 50 km above Earth’s surfacesurface

Upper stratosphere is warmer relative Upper stratosphere is warmer relative to the lower stratosphere because of an to the lower stratosphere because of an ozone layer absorbing solar radiationozone layer absorbing solar radiation

Ozone layer is important in shielding Ozone layer is important in shielding Earth from harmful solar UV (ultraviolet) Earth from harmful solar UV (ultraviolet) radiationradiation

MesosphereMesosphere Begins 50 km above Earth to 80 km Begins 50 km above Earth to 80 km

above Earthabove Earth Upper mesosphere is colder than Upper mesosphere is colder than

coldest region of stratospherecoldest region of stratosphere Region of atmosphere that protects Region of atmosphere that protects

Earth’s surface from being hit by most Earth’s surface from being hit by most meteoroids (meteors that have meteoroids (meteors that have entered Earth’s atmosphere)entered Earth’s atmosphere)

ThermosphereThermosphere Region of atmosphere 80 km and Region of atmosphere 80 km and

above Earth’s surfaceabove Earth’s surface Very low density atmosphereVery low density atmosphere Thermal energy of gases are very high Thermal energy of gases are very high

18001800o o C however, temperatures would C however, temperatures would be very low because of sparse density be very low because of sparse density of gas molecules to interact with of gas molecules to interact with thermometer or other objectsthermometer or other objects

Thermosphere Thermosphere (cont.)(cont.)

Thermosphere is composed of two layers, Thermosphere is composed of two layers, the ionosphere and the exospherethe ionosphere and the exosphere

Ionosphere starts at 80 km above Earth and Ionosphere starts at 80 km above Earth and extends to about 400 km above Earthextends to about 400 km above Earth

Ionosphere is the layer responsible for the Ionosphere is the layer responsible for the auroras (Northern and Southern lights)auroras (Northern and Southern lights)

Ionosphere also reflects AM and short wave Ionosphere also reflects AM and short wave radio waves back to Earth’s surfaceradio waves back to Earth’s surface

Exosphere begins at 400 km above Earth Exosphere begins at 400 km above Earth and extends for thousands of kilometers and extends for thousands of kilometers above Earth’s surfaceabove Earth’s surface

The End of The End of Atmosphere Atmosphere

CharacteristicsCharacteristics