Chapter Chapter 22.122.1

Characteristics of the Characteristics of the AtmosphereAtmosphere

What is the Atmosphere?What is the Atmosphere? AtmosphereAtmosphere – the layer of gases that – the layer of gases that

surrounds the Earth.surrounds the Earth.

The Two Functions of Our The Two Functions of Our Atmosphere:Atmosphere:

1.1.To protect the EarthTo protect the Earth’’s surface from s surface from the Sunthe Sun’’s radiation.s radiation.

2.2.To regulate the temperature of the To regulate the temperature of the EarthEarth’’s surface.s surface.

Chemical Composition of the Chemical Composition of the AtmosphereAtmosphere

Abundant Abundant ElementsElements

Nitrogen Nitrogen (78%)(78%)Oxygen Oxygen (21%)(21%)Argon Argon (0.9%)(0.9%)

Abundant Abundant CompoundsCompounds

Carbon dioxide Carbon dioxide (CO(CO22))

Water Vapor Water Vapor (H(H22O)O)

Water Vapor in the Water Vapor in the AtmosphereAtmosphere

The Two Process That Put Water Vapor Into Air Are:The Two Process That Put Water Vapor Into Air Are:1.1. EvaporationEvaporation

2.2. Transpiration (from plants)Transpiration (from plants)

The Two Process That Take Water Vapor Out of Air The Two Process That Take Water Vapor Out of Air Are:Are:

1. Condensation2. Precipitation

Based on Based on thethe time of time of day, location, day, location, andand

season, water vapor season, water vapor in in thethe atmosphere can vary atmosphere can vary from from asas low low asas 1% to 1% to asas

much much asas 4%. 4%.

Ozone (OOzone (O33) is a form of oxygen found in the ) is a form of oxygen found in the stratosphere (The stratosphere is the layer stratosphere (The stratosphere is the layer ABOVE the layer we live in which is called ABOVE the layer we live in which is called

the troposhere.). the troposhere.).

OzoneOzone is is created when ultraviolet radiationcreated when ultraviolet radiation (UV (UV rays)rays) fromfrom the the SunSun strikesstrikes and and splits splits oxygen oxygen

molecules molecules (O(O22)) toto atomic oxygen atomic oxygen (O).(O).

The atomic oxygen The atomic oxygen (O)(O) quickly quickly combinescombines with with further oxygen molecules further oxygen molecules to formto form ozone (Oozone (O33):):

Ozone

It should be noted that ground level (troposphere) ozone, which is produced by hydrocarbons that react with sunlight, is a

pollutant itself!!! Ground level ozone causes SERIOUS lung irritation!!!

OzoneOzone Before Earth had an ozone layer, all life lived

under the oceans … NONE could live above

them!Ozone absorbs harmful ultraviolet radiation (UV rays) coming from the

sun. Ultraviolet radiation

can cause severe burns, cancers, mutations, and

even death!). Ozone can be

destroyed by: CFC propellants in old

aerosol spray cans, Freon coolant from refrigerants in old

refrigerators and air conditioners, and

nitrogen oxide exhaust gases from burning supersonic jet fuel.

Dust In The Wind…Dust In The Wind…

Sources of Sources of Atmospheric Atmospheric Particulates:Particulates:

Dust from volcanic Dust from volcanic eruptionseruptions

Ash from firesAsh from fires Microscopic organismsMicroscopic organisms Minerals lifted from Minerals lifted from

soil by windssoil by winds Pollen from plantsPollen from plants

Particles from Particles from meteorite impactsmeteorite impacts

Salt from sea spraySalt from sea spray

ParticulatesParticulates – tiny solid particles in the – tiny solid particles in the air.air.

TheThe tinier tinier thethe particle, particle, thethe longer longer it can stayit can stay suspended suspended

in thein the air. air.

What is Atmospheric Pressure?What is Atmospheric Pressure?Atmospheric pressureAtmospheric pressure – the force per unit – the force per unit

area that is exerted on a surface by the area that is exerted on a surface by the weight of the atmosphere.weight of the atmosphere.

99% of the total mass of the atmosphere is located 99% of the total mass of the atmosphere is located within 32 km (20 miles) of the Earthwithin 32 km (20 miles) of the Earth’’s surface.s surface.

The general trend between atmospheric pressure and The general trend between atmospheric pressure and altitude is that, the higher up in the atmosphere one altitude is that, the higher up in the atmosphere one

goes, the less atmospheric pressure there will be.goes, the less atmospheric pressure there will be.

altitudealtitudepressurepressureA you go up in the atmosphere, the air gets thinner and therefore there A you go up in the atmosphere, the air gets thinner and therefore there

is less pressure. That is why ears pop when ascending and descending in is less pressure. That is why ears pop when ascending and descending in an airplane!an airplane!

Measuring Atmospheric Measuring Atmospheric PressurePressure

Measuring atmospheric pressure:Measuring atmospheric pressure: BarometerBarometer – a device used to measure atmospheric – a device used to measure atmospheric pressure. pressure. There are two types of barometers:There are two types of barometers: Mercury BarometerMercury Barometer – a barometer that works when air – a barometer that works when air pushes down on a pan of mercury forcing the mercury to rise pushes down on a pan of mercury forcing the mercury to rise up a calibrated, inverted tube.up a calibrated, inverted tube. Aneroid BarometerAneroid Barometer – a barometer that works when air – a barometer that works when air pressure squeezes on the sides of a can moving an attached pressure squeezes on the sides of a can moving an attached pointer.pointer.

Three values for Standard Pressure

(at sea level):1 atmosphere760 mm Hg1000 mb.

Did you know…Did you know…Mount Everest, Mount Everest,

the highest the highest elevation above elevation above

sea level, is sea level, is only about 8.8 only about 8.8

km high, km high, keeping it in keeping it in the bottom the bottom layer of the layer of the

atmosphere.atmosphere.

Layers of the Atmosphere 1

The Earth's atmosphere is composed of several layers: We live in the Troposphere where almost all weather occurs

(ex. wind, clouds, fog, rain, hail, sleet, snow and storms).

Above the Troposphere is the Stratosphere, which contains the Ozone Layer, which blocks out harmful UV rays.

Commercial airliners (ex. a 747) usually fly in the troposphere, whereas supersonic jet airliners (ex. the Concorde) fly in the lower

stratosphere.

Layers of the Atmosphere Layers of the Atmosphere 22

TroposphereTroposphere All weather change occurs here.All weather change occurs here. Temperature within this layer Temperature within this layer decreases as altitude increasesdecreases as altitude increases because there is an because there is an increase in increase in

distancedistance from the from the warming effect of warming effect of sunlightsunlight absorbed absorbed by the by the EarthEarth’’s s

surface.surface.

StratosphereStratosphereThe The Ozone LayerOzone Layer absorbsabsorbs harmful harmful

UV RaysUV Rays here, explaining the here, explaining the unexpected increase in temperature.unexpected increase in temperature.

MesosphereMesosphere Coldest layerColdest layer of the atmosphere of the atmosphere.

Temperature within this layer Temperature within this layer decreases as altitude increases.decreases as altitude increases.

ThermosphereThermosphere Lower regionLower region called called ionosphere.ionosphere. Upper regionUpper region called called exosphere.exosphere.

NitrogenNitrogen and and oxygenoxygen atoms atoms absorbabsorb deadly deadly gammagamma and and X raysX rays here, explaining the here, explaining the unexpected unexpected

increase in temperature.increase in temperature.

Air PollutionAir Pollution

The greatest source of air pollution todayThe greatest source of air pollution today is from is from the the burning of fossil fuelsburning of fossil fuels which which releasesreleases pollutants pollutants

such as such as sulfur dioxide gas (SOsulfur dioxide gas (SO22), hydrocarbons, ), hydrocarbons, nitrogen oxides (NO), carbon monoxide (CO), nitrogen oxides (NO), carbon monoxide (CO), and and

lead (Pb) lead (Pb) into the air.into the air.

These pollutants can cause These pollutants can cause irritating smog irritating smog which can which can make breathing difficult, especially for people with make breathing difficult, especially for people with asthma, allergies, and lung disease … asthma, allergies, and lung disease … OR cause …OR cause …

Acid Rain!!!Acid Rain!!!

All rain is somewhat naturally acidic!!

But when chemicals from car and factory exhaust (CO, CO2, NO, NO2, SO, SO2) combine with rainwater, they can produce HIGHLY

acidic rains that damage buildings and monuments and kill plants and fish.

The End!... The End!... Up Next … Light and the Up Next … Light and the

Electromagnetic Spectrum …Electromagnetic Spectrum …