the atmosphere: composition and structure

8/8/2019 The Atmosphere: Composition and Structure

1/31

THE ATMOSPHERE:THE ATMOSPHERE:

COMPOSITION ANDCOMPOSITION AND

STRUCTURESTRUCTURE


2/31

The AtmosphereThe Atmosphere

The atmosphere is the envelope of gases thatThe atmosphere is the envelope of gases thatsurround our planetsurround our planet

It is a very thin layer compared to the radius ofIt is a very thin layer compared to the radius ofthe Earththe Earth

We refer to this layer informally as airWe refer to this layer informally as air

The majority of the energy that drives theThe majority of the energy that drives theatmosphere is from the Sun.atmosphere is from the Sun.

The atmosphere receives most of this energyThe atmosphere receives most of this energy

from the surface.from the surface. Imbalances of energy drive the winds.Imbalances of energy drive the winds.

Eventually, all energy degrades down to friction.Eventually, all energy degrades down to friction.


3/31

Origin of the AtmosphereOrigin of the Atmosphere

Volcanoes release HVolcanoes release H22, CO, CO22, H, H22OOvv, N, N22, NH, NH33,,CHCH44

No ONo O22 or Oor O33, so no land organisms!, so no land organisms!

OneOne--celled aquatic organisms release COcelled aquatic organisms release CO22to atmosphere when breaking down foodto atmosphere when breaking down foodthrough fermentationthrough fermentation

Simple aquatic plants took in COSimple aquatic plants took in CO22 andandreleased Oreleased O22 to atmosphere viato atmosphere viaphotosynthesisphotosynthesis

OO33 formed from the Oformed from the O22


4/31

State of the AtmosphereState of the Atmosphere

We commonly express the state of theWe commonly express the state of theatmosphere by measuring it using theatmosphere by measuring it using thefollowing variables:following variables:

PressurePressure

TemperatureTemperature

WindWind

HumidityHumidity

Cloud coverCloud cover

Precipitation type and amountPrecipitation type and amount

Visibility (distance one can see horizontally)Visibility (distance one can see horizontally)


5/31

Types of MeasurementsTypes of Measurements

Contact MeasurementsContact Measurements Also calledAlso calledinin--situ measurements; Asitu measurements; Ameasurement that is conducted bymeasurement that is conducted by

sticking a probe into the mediumsticking a probe into the mediumbeing measured (thermometer).being measured (thermometer).

Remote SensingRemote Sensing A measurementA measurement

conducted by remote means and notconducted by remote means and notfrom directly within the mediumfrom directly within the mediumbeing measured (satellites).being measured (satellites).


6/31

The Relationship Between AirThe Relationship Between Air

Pressure and AltitudePressure and Altitude Pressure decreasesPressure decreases

as you go up inas you go up inheight.height.

The change inThe change inpressure is notpressure is notconstant. Theconstant. Thepressure decreasespressure decreasesexponentiallyexponentially withwithincreasing height.increasing height.


7/31

Pressure & DensityPressure & Density

Gravity pullsGravity pullsgases towardgases toward

earth's surface,earth's surface,

and the wholeand the whole

column of gasescolumn of gases

exerts a pressureexerts a pressure

of 1000of 1000

hectopascalhectopascal((hPahPa) at sea level.) at sea level.


8/31

Pressure and DensityPressure and Density

Decrease with HeightDecrease with Height


9/31

WeatherWeather

Weather is the state of theWeather is the state of theatmosphere at a particular time andatmosphere at a particular time and

a particular place.a particular place. An example of weather informationAn example of weather information

would be the temperature in Manilawould be the temperature in Manilatoday at 7 p.m.today at 7 p.m.


10/31

ClimateClimate

Climate is the longClimate is the long--term state of theterm state of theatmosphere at a particular location.atmosphere at a particular location.

Can be expressed as averages andCan be expressed as averages and

extremes.extremes. Normal conditions is simply a 30Normal conditions is simply a 30--yearyear

average of that particular variable.average of that particular variable.

Examples of climate information would be:Examples of climate information would be:

The normal high in Palawan on August 1 is 83The normal high in Palawan on August 1 is 83degrees.degrees.

The record amount of precipitation in PalawanThe record amount of precipitation in Palawanon August 1 is 2.55 inches back in 1961.on August 1 is 2.55 inches back in 1961.


11/31

More DefinitionsMore Definitions

Meteorology is the study of theMeteorology is the study of theEarths atmosphere, its motions andEarths atmosphere, its motions andbehaviorbehavior

Climatology is the study of theClimatology is the study of theEarths climate, its past and futureEarths climate, its past and future


12/31

Atmospheric CompositionAtmospheric Composition

Dry air (neglecting water vapor) isDry air (neglecting water vapor) iscomposed of the following gases:composed of the following gases:

Nitrogen (NNitrogen (N22)) = 78%= 78%

Oxygen (OOxygen (O22)) = 21%= 21%

Argon (Ar)Argon (Ar) = 1%= 1%

Trace GasesTrace GasesDust, bacteria, and other particulatesDust, bacteria, and other particulates


13/31


14/31


15/31

Atmospheric MoleculesAtmospheric Molecules

Note that the Oxygen, Nitrogen, andNote that the Oxygen, Nitrogen, andHydrogen that we breathe are notHydrogen that we breathe are notsingle atoms of that gas, but insteadsingle atoms of that gas, but insteadare two atoms of that gas bondedare two atoms of that gas bondedtogether in what is called a diatomictogether in what is called a diatomicmolecule.molecule.

Ozone is an example of a triatomicOzone is an example of a triatomicmolecule with three oxygen atoms.molecule with three oxygen atoms.


16/31

Atmospheric CompositionAtmospheric Composition

The dry air components in the air are wellThe dry air components in the air are well--mixed, meaning they do not vary widelymixed, meaning they do not vary widelywith location or time at the surface.with location or time at the surface.

Water vapor (HWater vapor (H22O) is a variable gas. YouO) is a variable gas. Youwill see it depends on temperature andwill see it depends on temperature andthe availability of liquid water. A volumethe availability of liquid water. A volume

of air can have between 0% and 4% waterof air can have between 0% and 4% watervapor, and this varies both in time andvapor, and this varies both in time andspace.space.


17/31

Vertical Layers of the AtmosphereVertical Layers of the Atmosphere

The Earths atmosphere has 4 distinctThe Earths atmosphere has 4 distinctlayers that are identified by the waylayers that are identified by the waytemperature changes with height.temperature changes with height.These layers are:These layers are:

-- TroposphereTroposphere

-- StratosphereStratosphere

-- MesosphereMesosphere

-- ThermosphereThermosphere


18/31

Atmospheric LayersAtmospheric Layers

8 layers are8 layers are

defined bydefined by

constant trendsconstant trends

in average airin average airtemperaturetemperature

(which changes(which changes

with pressurewith pressure

and radiation),and radiation),

where the outerwhere the outerexosphere isexosphere is

not shown.not shown.


19/31

TroposphereTroposphere

This is the layer closest to the EarthsThis is the layer closest to the Earthssurfacesurface

Almost all the weather phenomenonAlmost all the weather phenomenonwe know of occurs in this layer.we know of occurs in this layer.

The depth of the troposphere variesThe depth of the troposphere variesby the season (deeper in summer)by the season (deeper in summer)

Temperature on average decreasesTemperature on average decreaseswith height.with height.


20/31

StratosphereStratosphere

The next layer above the troposphereThe next layer above the troposphere

The boundary between the stratosphereThe boundary between the stratosphereand troposphere is called the tropopause.and troposphere is called the tropopause.

The ozone layer is found hereThe ozone layer is found here

Some clouds can form here near the polesSome clouds can form here near the poles

Temperature increases with heightTemperature increases with height

Very little mixing occurs between theVery little mixing occurs between thetroposphere and stratosphere.troposphere and stratosphere.


21/31

Mesosphere/ThermosphereMesosphere/Thermosphere

The mesosphere is the next layer above theThe mesosphere is the next layer above thestratosphere.stratosphere.

Clouds (noctilucent) are rare in the mesosphere.Clouds (noctilucent) are rare in the mesosphere.

The thermosphere rests above the mesosphere,The thermosphere rests above the mesosphere,and no clouds exist.and no clouds exist.

Temperature decreases with height in theTemperature decreases with height in themesosphere and increases with height in themesosphere and increases with height in thethermosphere.thermosphere.

The highest temperatures for the atmosphereThe highest temperatures for the atmosphereoccur in the thermosphere, but it doesnt feel hotoccur in the thermosphere, but it doesnt feel hotbecause the atmosphere is so thin up there.because the atmosphere is so thin up there.


22/31

Atmospheric DensityAtmospheric Density

Density and pressure in theDensity and pressure in theatmosphere decrease exponentiallyatmosphere decrease exponentiallywith heightwith height

Approximately 75% of the totalApproximately 75% of the totalatmosphere is in the troposphereatmosphere is in the troposphere

Approximately 99% of theApproximately 99% of theatmosphere is the troposphere andatmosphere is the troposphere andstratospherestratosphere


23/31

Biogeochemical CyclesBiogeochemical Cycles

The following are contributoriesThe following are contributoriesto the composition of theto the composition of the

atmosphere:atmosphere: Nitrogen CycleNitrogen Cycle

Carbon Dioxide CycleCarbon Dioxide Cycle

Oxygen CycleOxygen Cycle


24/31

Nitrogen CycleNitrogen Cycle


25/31

Carbon CycleCarbon Cycle


26/31

Oxygen CycleOxygen Cycle


27/31

Heat Transfers in the AtmosphereHeat Transfers in the Atmosphere

Heat transfersHeat transfersfrom high tofrom high tolow temps.low temps.

There areThere arethree means:three means:

ConductionConduction

ConvectionConvection RadiationRadiation


28/31

Heat TransferHeat Transfer -- ConductionConduction

Conduction occurs whenConduction occurs whenheat is transferredheat is transferredmolecule to moleculemolecule to molecule

Solids including wet soilSolids including wet soil

are good conductorsare good conductors CalmCalm air is a poorair is a poor

conductor; the heat hardlyconductor; the heat hardlytravels by conduction a fewtravels by conduction a fewcentimeters from surfacecentimeters from surfacein into the atmosphere.in into the atmosphere.

But we know heat fromBut we know heat fromsurface can reachsurface can reachkilometers high.kilometers high.


29/31

Heat TransferHeat Transfer -- ConvectionConvection

It is because the atmosphere is seldomIt is because the atmosphere is seldomcalm; rather it often moves up and down.calm; rather it often moves up and down.

Mass movement in vertical caries heatMass movement in vertical caries heatwith itwith it

Heated air is less dense, expands, andHeated air is less dense, expands, andrisesrises starts thermals.starts thermals.

Cooler, denser air sinks to replace warmCooler, denser air sinks to replace warmairair completes convective cycle.completes convective cycle.

This vertical heat transfer is known asThis vertical heat transfer is known asconvection.convection.


30/31


31/31

RadiationRadiation

What is radiation? It is the energy inWhat is radiation? It is the energy intransient and is also called radiant energy.transient and is also called radiant energy.

Recall we also said radiation is a meansRecall we also said radiation is a means

of energy transfer in parallel toof energy transfer in parallel toconduction and convection.conduction and convection.

Radiation is also viewed as stream ofRadiation is also viewed as stream ofparticle called photons that carries energy.particle called photons that carries energy.

As a means of transfer, radiation travels inAs a means of transfer, radiation travels inelectromagnetic waves.electromagnetic waves.

the atmosphere: composition and structure

Documents