1. week 1 earth, air pressure,cloud.ppt

8/10/2019 1. Week 1 Earth, air pressure,cloud.ppt

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Earth An oxygen-rich and protective atmosphere,moderate temperatures, abundant water,and a varied chemical composition allowearth to support life,


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SCE 3110 EARTH AND SPACE

Earth as a planetThe atmosphereClouds

Air pressure


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The Earth and the other 8 planets and the Sun are

created at about the same time from a vast cloudof dust and gas (nebula).

About 5 billion years ago, the nebula began to

gravitationally contract, began to rotate andflattened.

Eventually, the Sun ignited (fusion) and thenewly formed planets began to differentiate -heavier elements and chemical components sankto the center and rocky material formed the crust.

The newly formed planets and moons released

gas forming early atmospheres.

The Origin of the Earth


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Visualizing Physical GeographyCopyright 2008 John Wiley and Sons Publishers Inc.

- About 4.54 billion years ago the Earth and theother planets in the Solar System formed outof the solar nebula - disk-shaped mass ofdust and gas left over from the formation ofthe Sun

- Initially molten, the outer layer of the planet

Earth cooled to form a solid crust when waterbegan accumulating in the atmosphere.


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A cometary bombardment during the early

history of the planet played a role in theformation of the oceans.

Later, asteroid impacts caused significantchanges to the surface environment.



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The Moon formed soon afterward, possibly as theresult of a Mars-sized object with about 10% of theEarth's mass impacting the Earth in a glancing blow.

Some of this object's mass would have merged withthe Earth and a portion would have been ejected intospace, but enough material would have been sentinto orbit to form the Moon.

Outgassing and volcanic activity produced theprimordial atmosphere.



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Condensing water vapor , augmented by ice and liquid

water delivered by asteroid s and the larger proto-planets ,comets , and trans-Neptunian objects produced theoceans

Beginning with almost no dry land , the total amountof surface lying above the oceans has steadilyincreased. During the past two billion years, forexample, the total size of the continents has doubled.

On time scales lasting hundreds of millions of years,the surface continually reshaped itself as continentsformed and broke up.



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The continents migrated across the surface,occasionally combining to form a supercontinent

Roughly 750 million years ago ( mya ), one of the

earliest known supercontinents, Rodinia , began tobreak apart.

The continents later recombined to form Pannotia ,

600 540 mya, then finally Pangaea , which brokeapart 180 mya.
http://en.wikipedia.org/wiki/Mya_%28unit%29http://en.wikipedia.org/wiki/Rodiniahttp://en.wikipedia.org/wiki/Pannotiahttp://en.wikipedia.org/wiki/Pangaeahttp://en.wikipedia.org/wiki/Pangaeahttp://en.wikipedia.org/wiki/Pannotiahttp://en.wikipedia.org/wiki/Rodiniahttp://en.wikipedia.org/wiki/Mya_%28unit%29


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Earth as Planet3rd planet from the Sun (150 million kilometers)takes 365.256 days travel around the Sun23.9345 hours rotates a complete revolution.

largest of the terrestrial planets in the Solar System indiameter, mass and density.

referred to as the World and Terra

About 71% of the surface is covered with salt-wateroceans (continent + island )


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Earth as Planet

Rapid spin & molten nickel-iron corecreates magnetic fieldalong with atmosphere protect us fromharmful radiationMeteors burn up in the atmosphere beforethey can strike the surface.


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Earth Statistics

Mass (kg) 5.976e+24

Mass (Earth = 1) 1.0000e+00

Equatorial radius (km) 6,378.14

Equatorial radius (Earth = 1) 1.0000e+00

Mean density (gm/cm^3) 5.515

Mean distance from the Sun (km) 149,600,000

Mean distance from the Sun (Earth = 1) 1.0000

Rotational period (days) 0.99727

Rotational period (hours) 23.9345

Orbital period (days) 365.256 Mean orbital velocity (km/sec) 29.79

Orbital eccentricity 0.0167

Tilt of axis (degrees) 23.45

Orbital inclination (degrees) 0.000

Equatorial escape velocity (km/sec) 11.18

Equatorial surface gravity (m/sec^2) 9.78

Visual geometric albedo 0.37

Mean surface temperature 15 C

Atmospheric pressure (bars) 1.013

Atmospheric compositionNitrogenOxygenOther

77%21%

2%

Earth

An oxygen-rich and protective

atmosphere, moderate temperatures,abundant water, and a varied chemicalcomposition allow earth to support life.


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The Earth System I

The global interconnections of air,

water, rocks and life.

Earth system science is the study of the

whole earth as a system of manyinteracting parts.


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There are four reservoirs of materialon the earth.

These are:(1) the geosphere(2) the atmosphere,(3) the hydrosphere(4) the biosphere.

The Earth System II


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The amount of matter that enters orleaves the Earth system is so smallcompared with the mass of the systemthat the Earth can be considered a closedsystem.

Because the amount of matter in aclosed system is finite , the mineralresources on this planet are also finite.

The Earth System III


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Earth: Open or Closed System?


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Earth:Matter does not come and go

Earth is aClosedSystem

to Matter

So matter is

constantlyrecycled on

Earth


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Earth:Earth constantly gains & loses energy

Earth is aOpen

Systemto Energy

Heat

Sunlight


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Earth: Open or Closed System?

Mostly Open to Energy

Mostly Closed to Matter


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The whole earth is a closed system , butall of its innumerable smaller parts are

open systems and both matter and energycan be transferred between them. Theatmosphere, hydrosphere, biosphere, and

geosphere are all open systems.

The Earth System IV


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Sunlight

Evaporation from lakes,streams and soils

RainTranspiration

SeaWater from streams and groundwater flows to the sea

OPEN SUB-SYSTEM OF THE EARTH


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The Earth System VI Energy reaches

the Earth inabundance in theform of solarradiation andleaves the earth inthe form ofinfrared radiation.

Biosphere

Short Wave Radiation

Long Wave Radiation

Sun

Atmosphere

Geosphere Hydrosphere


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Earths Sphere

Atmosphere

Hydrosphere Lithosphere Biosphere

The Earth iscomposed of several

integrated parts thatinteract with oneanother: spheres


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Lithosphere - Al l processes associated with the solid earthHydrosphere - Al l processes associated wi th waterAtmosphere - All pr ocesses associated with the gases that envelope the ear thBiosphere - Al l processes that i nvolve living organi sms


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Atmosphere A gaseous sphere

and it envelopes theEarth

Consists of a mixtureof gases composedprimarily of nitrogen,oxygen, carbondioxide, and water

vapor.Nitrogen 78.0842%Oxygen 20.9463%

Argon 0.9342%Carbon dioxide 0.0384%

Other 0.0020%


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Atmosphere

Ozone at thislayer

4 major layers.


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Atmosphere

Protects life on Earth by; absorbing ultraviolet solar radiation, warming the surface through heat

retention (greenhouse effect), reducing temperature extremes

between day and night.


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Atmosphere

Temperaturechange withlatitude.


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Structure of the Atmosphere

Thermosphere

Mesosphere

Ozone Maximum

Stratosphere

Troposphere

Temperature


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Hydrosphere

All of thewater onEarth

71% of theearth iscovered bywater andonly 29% isterra firma


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Biosphere All life on earth,

including man,and all organisms.

The life zone onour planetdistinguishes ourplanet from theothers in the solarsystem.


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Cryosphere The portion of

the Earth'ssurface where

water is in a solidform

Snow or ice:

includes glaciers,ice shelves,snow, icebergs,and arctic

climatology


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Anthrosphere

Man and hisdirectancestors,hominids.

The humanpopulation, itsbuildings,dams,and otherconstructions.


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Cloud

Condensation results in dew, fog or cloudWater vapors need a surface to condense.

Eg grass, leaves, car screen = dewFog consequence of radiation; cooling ormoving air over a cold surface.


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Cloud

How about in the air above ground?Condensation nuclei tiny bits particulatematters (dust, smoke & salt particles calledhygroscopic nuclei absorb water)Without condensation nuclei humid atmos.


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Cloud

Water vapor absorbed by these particlesbecome visible as clouds.

If clouds form below freezing temp.,tiny ice crystals form.


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Cloud

droplets orfrozen crystalsfloating in theatmosphereprovide visibleindication.


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Condensation & Cloud Formation (4Condensation I

When air becomes saturated with water, eitherwater condenses or ice crystals precipitatedepending on the temperature.

Condensed cloud droplets are so small that airturbulence keeps them suspended. However astheir density increases they start to coalesce(combine) and fall. As they fall these furthercoalesce with droplets they bump into andeventually a rain drop is formed. The formationof sleet (frozen rain), and in particular snow, ismore complex.


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Condensation & Cloud Formation (4Condensation II

Process II - supercooledwater dropletsevaporate, & icecrystals grow byincorporating newlyformed water vapour

Process I


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Condensation & Cloud Formation


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When precipitation occurs (rain)?

Cloud consisting millions of tiny waterdroplets (20 micrometer) suspended inair.Human hair diameter 75 micrometerRain drop diameter 2000 micrometer

# million times the vol. of cloud droplet.Precipitation needs additional waterdroplets and collision.

C d ti & Cl d F ti (5


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Condensation & Cloud Formation (5Clouds 1

Clouds form when air rises and becomes saturated inresponse to adiabatic cooling. There are 4 reasons for the upward movement of air:

1. Density lifting - warm, low density air risesconvectively displacing cooler dense air.

2. Frontal Lifting - occurs when 2 flowing air 3. Orographic Lifting - occurs when flowing air is

forced upward as a resulting of a slopingterrain (west coast of Tasmania) 4. Convergence Lifting - occurs when flowing air

masses converge & are forced upwards.


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B & C Frontal Lifting - boundaries b/w air masses of different temp. &humidity are called fronts. May getwarm fronts or cold fronts (10 -150kms in width)

Condensation & Cloud Formation (5


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Clouds are visible aggregations of minute waterdroplets, tiny ice crystals or both.

Since clouds form by condensation of watervapour, all common clouds are phenomena of the

troposphere.

Condensation & Cloud Formation (5Clouds III


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Clouds are classified on the basis of shape, appearance

and height into 3 families: cumulus, stratus, and cirrus .



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Cumulus clouds are puffy, globular,individual clouds thatform when hot, humid

air rises convectively.

Cumulus Cumulonimus

Altocumulus


Clouds V

Condensation & Cloud Formation (8)


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Condensation & Cloud Formation (8)Clouds VI

Cirrostratus Stratocumulus

Stratus Altostratus

Stratus Clouds aresheets of cloud thatform at altitudesfrom 2-15 kms andgenerally cover theentire sky. Theyform as aconsequence offrontal lifting.

Nimbostratus


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Types of Cloud

2 categories: layered and convective.stratus clouds or stratiform means "layer"and cumulus clouds or cumuliform means"piled up.

High clouds (Family A)CirrocumulusCirrus cloudCirrostratus

Middle clouds (Family B) Altostratus

Altocumulus

Classification


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Cloud

Low clouds (Family C)include the stratuswhich contact theground called fog.

CumulusCumulus humilisCumulus mediocrisStratocumulusNimbostratusStratus

Vertical clouds (Family D)Cumulonimbus(associated with heavyprecipitation and

thunderstorms)Cumulonimbus calvusCumulonimbus incusCumulonimbus

CumulusCumulus congestusPyrocumulus

Classification


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Air Pressure Gas molecules bombard

randomly againstsurfaces in all directions;

As air density increases,the number of strikesper unit time & area alsoincreases thus exertedforce (higher pressure).

As altitude increases,the number of moleculesdecreases, meaning adecrease in air pressure.

Composition & Structure of the


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Composition & Structure of theAtmosphere (20)

Air Pressure III Air pressure decreases with

altitude because air iscompressible and behaveslike a pile of springs.

(A) The springs near thebase are compressed by theweight of the springsabove.

(B) Air is similarlycompressed by the weightof the air above.


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Air Pressure Atmosphere extends more than 15

miles (24 km) up;

one half of the air molecules in theatmosphere are contained within thefirst 18,000 feet (5.6 km).

Pressure produced by weight of airconfined in the atmosphere.

Composition & Structure of the


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Composition & Structure of theAtmosphere (19)

Air Pressure II If a helium balloon 1m in

diameter is released at sealevel, it expands as it floatsupward because of the pressuredecrease.

This emphasised thecompressible nature of gases(including atmospheric gases)


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Air Pressure

Air pressure is measured with adevice called a barometer.

At sea level 1kg/cm2

1013.2 millibars 29.92 inches of mercury Producing changes to weather Variations between places;

generates winds & bringchanges in temperature &humidity.


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Reference

Skinner et. al., 1999 The Blue

Planet (2nd Edition), Chapter 12.

1. week 1 earth, air pressure,cloud.ppt

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