The AtmosphereThe Atmosphere

Weather vs. climateWeather vs. climate

Weather: The state of the atmosphere at Weather: The state of the atmosphere at a given time (hour to hour or day to day)a given time (hour to hour or day to day)

Climate: A description of aggregate Climate: A description of aggregate weather conditions, based on observations weather conditions, based on observations that take place in a region over a period of that take place in a region over a period of yearsyears

Basic elements of weather & Basic elements of weather & climateclimate

Air temperatureAir temperatureHumidityHumidityType and amount of cloudinessType and amount of cloudinessType and amount of precipitationType and amount of precipitationAir pressureAir pressureThe speed and direction of the windThe speed and direction of the wind

Composition of the AtmosphereComposition of the Atmosphere

Nitrogen: 78%Nitrogen: 78%Oxygen: 21%Oxygen: 21%Other gases 1%Other gases 1%

Carbon dioxideCarbon dioxide

Formula: COFormula: CO22

Absorbs heat energy radiated by earthAbsorbs heat energy radiated by earth Influences heating of the atmosphereInfluences heating of the atmosphere

Water vaporWater vapor

Formula: HFormula: H22OOVaries from 0-4% compositionVaries from 0-4% compositionSource of all clouds and precipitationSource of all clouds and precipitationAbsorbs or release heat energy (latent Absorbs or release heat energy (latent

heat)heat)

OzoneOzone

Formula: OFormula: O33

Ozone is concentrated in the stratosphereOzone is concentrated in the stratosphereOzone absorbs harmful ultraviolet Ozone absorbs harmful ultraviolet

radiation from the sunradiation from the sunOzone is being slowly depleted from the Ozone is being slowly depleted from the

atmosphere due to use of atmosphere due to use of chlorofluorocarbons (CFC’s)chlorofluorocarbons (CFC’s)

Structure of the AtmosphereStructure of the Atmosphere

Four layers of the atmosphereFour layers of the atmosphere

1) Troposphere tropopausetropopause

2) Stratosphere stratopausestratopause

3) Mesophere mesopausemesopause

4) Thermosphere

Structure of the Atmosphere Structure of the Atmosphere (cont.)(cont.)

50% of our atmosphere lies below an 50% of our atmosphere lies below an altitude of 3.5 miles above the Earth’s altitude of 3.5 miles above the Earth’s surfacesurface

TroposphereTroposphere

The bottom layer of the atmosphereThe bottom layer of the atmosphereVirtually all life exists in this layerVirtually all life exists in this layerThis layer is responsible for all our This layer is responsible for all our

weatherweatherTemperature of troposphere decreases Temperature of troposphere decreases

with increasing altitude (3.5with increasing altitude (3.5ooF per 1000 ft.)F per 1000 ft.)Outer boundary is called the tropopauseOuter boundary is called the tropopause

StratosphereStratosphere

This layer lies beyond the tropopauseThis layer lies beyond the tropopauseTemperature remains constant to height of Temperature remains constant to height of

13 miles, then the temperature will 13 miles, then the temperature will gradually increasegradually increase

Ozone is concentrated in this layerOzone is concentrated in this layerOuter layer is called the stratopauseOuter layer is called the stratopause

MesosphereMesosphere

Temperature decreases gradually with Temperature decreases gradually with increasing height until one reaches the increasing height until one reaches the mesopausemesopause

At that point temperature reaches around At that point temperature reaches around

-90-90ooC (-130C (-130ooF)F)

ThermosphereThermosphere

Layer extends beyond the mesopauseLayer extends beyond the mesopauseTemperature rise rapidly and are very high Temperature rise rapidly and are very high

(>1000(>1000ooC or 1800C or 1800ooF)F)

Earth-Sun relationshipsEarth-Sun relationships

Virtually all the energy that drives the Virtually all the energy that drives the earth’s weather comes from the sunearth’s weather comes from the sun

Solar energy is not evenly distributed over Solar energy is not evenly distributed over the earth’s surface. Amount of energy the earth’s surface. Amount of energy depends on latitude and seasondepends on latitude and season

Wind and currents are due to unequal Wind and currents are due to unequal heating of the earthheating of the earth

Earth’s motionsEarth’s motions

Two principal motions:Two principal motions:

1) rotation: Spinning of the earth about its 1) rotation: Spinning of the earth about its axisaxis

2) revolution: movement of the earth 2) revolution: movement of the earth about the sun.about the sun.

When the Earth orbits the Sun, the Earth When the Earth orbits the Sun, the Earth tilts 23 1/2 degrees from the tilts 23 1/2 degrees from the perpendicularperpendicular

This is called the This is called the inclination of the axisinclination of the axis

The greater the angle of the sun, the more The greater the angle of the sun, the more concentrated to the Earth’s surface.concentrated to the Earth’s surface.

The sun’s angle is highest in summer, and The sun’s angle is highest in summer, and lowest in the winterlowest in the winter

SeasonsSeasons

Seasons are based on two contributing Seasons are based on two contributing factors:factors:

a) length of daylighta) length of daylight

b) angle of the sunb) angle of the sun

During the summer solstice (June 21), the During the summer solstice (June 21), the Northern Hemisphere is leaning 23 ½ Northern Hemisphere is leaning 23 ½ degrees degrees towards the suntowards the sun

During the winter solstice (December 21), During the winter solstice (December 21), the Northern Hemisphere is leaning 23 ½ the Northern Hemisphere is leaning 23 ½ degrees away degrees away from the sunfrom the sun

During the autumnal and spring equinoxes During the autumnal and spring equinoxes (September 22 & March 21), the Earth is (September 22 & March 21), the Earth is tilted 0tilted 0oo from the sun. from the sun.

Facts about the summer solsticeFacts about the summer solstice

Occurs June 21 or 22Occurs June 21 or 22Vertical rays of the sun are striking the Vertical rays of the sun are striking the

Tropic of Cancer (23 ½ north latitude)Tropic of Cancer (23 ½ north latitude)Northern Hemisphere are experiencing the Northern Hemisphere are experiencing the

greatest length of daylightgreatest length of daylightLocations north of the Tropic of Cancer Locations north of the Tropic of Cancer

are experiencing the highest noon Sun are experiencing the highest noon Sun anglesangles

The farther you are north of the equator, The farther you are north of the equator, the longer the period of daylight, until the the longer the period of daylight, until the Arctic Circle is reached, where the daylight Arctic Circle is reached, where the daylight lasts for 24 hourslasts for 24 hours

The opposite occurs during the winter The opposite occurs during the winter solsticesolstice

Heat & Heat transferHeat & Heat transfer

Heat: Form of energy that moves from a Heat: Form of energy that moves from a warmer body to a cooler bodywarmer body to a cooler body

If two objects of unequal temperature are If two objects of unequal temperature are in contact with each other, heat will travel in contact with each other, heat will travel from the warmer body to the cooler body.from the warmer body to the cooler body.

The temperature of the warmer will The temperature of the warmer will decrease, temperature of the cooler body decrease, temperature of the cooler body will increasewill increase

Mechanisms of Heat TransferMechanisms of Heat Transfer

1)1) ConductionConduction

2)2) ConvectionConvection

3)3) radiationradiation

ConductionConduction

Transfer of heat through matter by Transfer of heat through matter by molecular activity (direct contact)molecular activity (direct contact)

Transfer occurs by collisions from one Transfer occurs by collisions from one molecule to anothermolecule to another

Conduction of heat varies from one Conduction of heat varies from one material to anothermaterial to another

Metals are the best heat conductorsMetals are the best heat conductors

ConvectionConvectionTransfer of heat by mass movement or Transfer of heat by mass movement or

circulation within a substancecirculation within a substanceConvection primarily takes place in fluidsConvection primarily takes place in fluidsThis is the type of heat transfer that primarily This is the type of heat transfer that primarily

occurs in the atmosphereoccurs in the atmosphere

RadiationRadiation

Transfer of energy through a vacuum or Transfer of energy through a vacuum or spacespace

Solar energy reaches our planet by way of Solar energy reaches our planet by way of radiationradiation

Forms of RadiationForms of Radiation

1)1) VisibleVisible

2)2) InfraredInfrared

3)3) UltravioletUltraviolet

4)4) X-raysX-rays

5)5) MicrowavesMicrowaves

6)6) radiowavesradiowaves

Radiation (cont.)Radiation (cont.)

All these radiations constitutes a collection All these radiations constitutes a collection of radiations called an electromagnetic of radiations called an electromagnetic spectrumspectrum

Each of these radiations have a Each of these radiations have a characteristic wavelengthcharacteristic wavelength

Wavelength: Distance from one crest to Wavelength: Distance from one crest to the nextthe next

Visible radiationVisible radiation

Radiation which can be seen by our eyes.Radiation which can be seen by our eyes.Visible radiation can be broken down into Visible radiation can be broken down into

its seven colors (what are the colors?)its seven colors (what are the colors?)

Infrared radiationInfrared radiation

Radiation is longer in wavelength than Radiation is longer in wavelength than visible lightvisible light

Lies above the red region of the visible Lies above the red region of the visible spectrumspectrum

Responsible for heat radiationResponsible for heat radiation

Ultraviolet radiationUltraviolet radiation

Shorter wavelength than visible radiationShorter wavelength than visible radiationLies below the violet region of the visible Lies below the violet region of the visible

spectrumspectrumPrimary source of radiation from the sun. Primary source of radiation from the sun.

Responsible for sunburnResponsible for sunburn

Basic Laws of RadiationBasic Laws of Radiation

1)1) All objects give off radiation, regardless All objects give off radiation, regardless of temperatureof temperature

2)2) Hotter objects give off more radiation Hotter objects give off more radiation than colder objectsthan colder objects

3)3) The hotter the radiating body, the shorter The hotter the radiating body, the shorter the wavelength of maximum energythe wavelength of maximum energy

4)4) Objects that are good absorbers are also Objects that are good absorbers are also good emitters as wellgood emitters as well

Fate of incoming solar radiationFate of incoming solar radiation

When radiation strikes an object, three When radiation strikes an object, three possible outcomes can occur:possible outcomes can occur:

1) Radiation can be absorbed by the object1) Radiation can be absorbed by the object

2) Radiation can be transmitted (go 2) Radiation can be transmitted (go through) the objectthrough) the object

3) Radiation can be reflected (bounced off) 3) Radiation can be reflected (bounced off) an objectan object

Solar radiation and our EarthSolar radiation and our Earth

About 50% of the solar energy reaching About 50% of the solar energy reaching the atmosphere is absorbed by the Earth’s the atmosphere is absorbed by the Earth’s surfacesurface

About 30% is reflected back into space by About 30% is reflected back into space by the atmosphere, clouds, and other the atmosphere, clouds, and other reflective surfacesreflective surfaces

About 20% is absorbed by clouds and the About 20% is absorbed by clouds and the atmosphere’s gasesatmosphere’s gases

ReflectionReflection

About 30% of the solar energy reaching About 30% of the solar energy reaching the outer atmosphere is reflected back to the outer atmosphere is reflected back to the spacethe space

This fraction of total radiation that is This fraction of total radiation that is reflected is called albedoreflected is called albedo

ScatteringScattering

Occurs when a beam of light produces a Occurs when a beam of light produces a larger number of weaker rayslarger number of weaker rays

The weaker rays travel in all directionsThe weaker rays travel in all directionsScattering of light accounts for the Scattering of light accounts for the

blueness of our skyblueness of our sky

AbsorptionAbsorption

Gases are selective absorbersGases are selective absorbersNitrogen is a poor absorber of solar Nitrogen is a poor absorber of solar

radiationradiationOxygen removes most of the shorter Oxygen removes most of the shorter

wavelength ultraviolet radiation and ozone wavelength ultraviolet radiation and ozone absorbs most of the ultraviolet rays from absorbs most of the ultraviolet rays from the stratospherethe stratosphere

Factors affecting albedoFactors affecting albedo

Amount of cloud coverAmount of cloud coverSun’s angleSun’s anglePresence of particulate matterPresence of particulate matterNature of the Earth’s surfaceNature of the Earth’s surface

The greenhouse effectThe greenhouse effect

This is the increase in the temperature of a This is the increase in the temperature of a planet’s atmosphere caused when planet’s atmosphere caused when infrared-absorbing gases are introduced infrared-absorbing gases are introduced into the atmosphereinto the atmosphere

Greenhouse gasesGreenhouse gases

Carbon dioxideCarbon dioxideWater vaporWater vaporWithout the greenhouse effect, life on our Without the greenhouse effect, life on our

planet will not existplanet will not exist

Temperature controlsTemperature controls

A factor that causes temperature to vary A factor that causes temperature to vary from place to place and from time to timefrom place to place and from time to time

Why Temperatures VaryWhy Temperatures Vary

Factors other than latitude that exert a Factors other than latitude that exert a strong influence on temperature include strong influence on temperature include heating of land and water, altitude, heating of land and water, altitude, geographic position, cloud cover, and geographic position, cloud cover, and ocean currents.ocean currents.

Temperature ControlsTemperature Controls

Land and WaterLand and WaterLand heats more rapidly and to higher Land heats more rapidly and to higher

temperatures than water. Land also cools temperatures than water. Land also cools more rapidly and to lower temperatures than more rapidly and to lower temperatures than water.water.

Geographic PositionGeographic Position

The geographic setting can greatly The geographic setting can greatly influence temperatures experienced at a influence temperatures experienced at a specific location.specific location.

Leeward vs. WindwardLeeward vs. WindwardRain ShadowRain Shadow

AltitudeAltitude

The altitude can greatly influence The altitude can greatly influence temperatures experienced at a specific temperatures experienced at a specific location.location.

The higher into the troposphere, the cooler The higher into the troposphere, the cooler the temperaturethe temperature

Cloud Cover and AlbedoCloud Cover and Albedo

Albedo is the fraction of total radiation that is the fraction of total radiation that is reflected by any surface.is reflected by any surface.

Many clouds have a high albedo and Many clouds have a high albedo and therefore reflect back to space a therefore reflect back to space a significant portion of the sunlight that significant portion of the sunlight that strikes them.strikes them.

AlbedoAlbedo

The fraction of radiation that is reflected by The fraction of radiation that is reflected by the earth’s surfacethe earth’s surface

Albedo of the Earth, as a whole is 30%Albedo of the Earth, as a whole is 30%Albedo varies on Earth from place to place Albedo varies on Earth from place to place

and from time to timeand from time to time

50% of the solar energy that strikes the 50% of the solar energy that strikes the Earth’s surface is absorbedEarth’s surface is absorbed

Most of this radiation is radiated skywardMost of this radiation is radiated skywardThe radiation that the Earth gives off has The radiation that the Earth gives off has

longer wavelengths than solar radiationlonger wavelengths than solar radiation

World Distribution of World Distribution of TemperatureTemperature

Isotherms are lines on a weather map are lines on a weather map that connect points where the temperature that connect points where the temperature is the same.is the same. Isotherms generally trend east and west and Isotherms generally trend east and west and

show a decrease in temperatures from the show a decrease in temperatures from the tropics toward the poles.tropics toward the poles.