atmospheric temperature

8/11/2019 Atmospheric Temperature

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Elements of Climate

Temperature

Rainfall


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Temperature

Temperature is a

measure of the

average kineticenergy (motion) of

individual

molecules ofmatter.


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Heat

Heat is a form ofenergy that flows

from one system or

object to anotherbecause the two are

at different

temperatures.


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Relation between heat &

temperature

Changes in temperature are caused bygain or loss of heat energy.

Heat Gained- Higher temperature

Heat Lost- Lower temperature


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Earth's Atmosphere

99% of atmospheric gases, including water vapor, extend only 30 kilometer (km)

above earth's surface.

Most of our weather, however, occurs within the first 10 to 15 km.

Figure 1.2

Thin Gaseous envelope


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ATMOSPHERIC TEMPERATURE

This diagram shows the

average global temperature of

air at altitude.

Temperature tends to decrease

with altitude

Temperature inversions(when

it increaseswith altitude) occurwhere various gasescause

varying rates absorption of

radiation

Greenhouse gases

ENVIRONMENTAL LAPSE RATE


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Lapse Rate

The rate at which air temperature

decreases with height.

The standard (average) lapse rate in the

lower atmosphere is about 6.5C per 1

km.

i.e.1 C per 165 m

At h i L


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Atmospheric Layers

Figure 1.7

TroposphereTemp decrease w/ heightMost of our weather occurs in this layer

Varies in height around the globe, but

Averages about 11 km in height.

At h i L


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Atmospheric Layers

Figure 1.7

Stratosphere

Temperature inversion in stratosphere

Ozone plays a major part in heating the air

at this altitude

At h i L


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Atmospheric Layers

Figure 1.7

Mesosphere

Middle atmosphereAir thin, pressure low,

Need oxygen to live in this region. Air

quite Cold -90C (-130F) near the top ofmesosphere

At h i L


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Atmospheric Layers

Figure 1.7

Thermosphere

Hot layer oxygen molecules absorbenergy from solar Rays warming the air.

Very few atoms and molecules in this

region.


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EarthAtmosphere Energy

System Earths atmosphere and surface are driven

by the suns radiant energy.

This solar energy is unevenly distributed

by latitude.

The Earth-Atmosphere Energy System

includes incoming shortwave radiation

(UV light) and outgoing longwave

radiation (thermal infrared).


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Earths Energy Balance

100 units

51 units

14 units

51 units

34 units

17 units


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Insolation intensity decreases as one moves

away from the Equator

The Equator receives maximum insolation assun rays are perpendicular to the surface.

G O A A A O S i SO A O


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GLOBAL VARIATIONS in INSOLATION

Atmospheric

gases, dust andvapour absorb

more energy

before it reaches

the earths

surface.

Radiation

passes through

a greater

length ofatmosphere

when at a low

angle in the

sky than when

overhead.


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CONTINENTAL SCALE VARIATIONSSatellite photo

taken in daytime

in June over

Scandinavia.

Warmer surfaces

show darker. Note

that land is darker

than sea (ie land is

warmer).

Satellite photo

taken at night

over Britain in

January. Warmsurfaces show

darker. Note that

sea is darker

than the land (ie

sea iswarmer).

REASONS FOR CONTINENTAL

TEMPERATURE CONTRASTS

Water has a higher specific heat than land

ie: it takes more energy to heat up an equalmass of water by 1C than it does land. Water

stores heat energy more effectively than land.

Insolation is concentrated into the top few

cm of the land, but is dispersed over the

surface 10-20m of water.

EFFECTSTemperatures of the sea vary less than on land

Land near the sea has temperatures moderated

The larger the ocean, the greater the effect

Land temperatures vary more; the larger the landmass, the larger the variation of temperature.

Continental scale land masses have a more

seasonal climate.


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Marine Effect & Continental Effect

Marine Effect (Maritime):Areas next to

oceans exhibit more moderate temperature

characteristics.

Continental Effect:Areas less affected by

the ocean have a greater range betweenmaximum and minimum temperatures,

both daily and yearly.


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Altitude

The Troposphere extends from the Earths surfaceto 18km. Within the Troposphere, temperatures decrease with

increasing altitude above Earths surface.

Temperatures decrease at an average of 6.4C per kilometer.(Normal Lapse Rate ).

Worldwide, mountainous areas experience lower

temperatures than do regions nearer sea level, even

at similar latitudes.


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Altitude

At higher elevations:

average air temperatures are lower

nighttime cooling is greater the temperature range between day and night is greater

than at low elevations.

The density of the atmosphere also diminishes

with increasing altitude.

ability to absorb and radiate sensible heat is reduced


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ALBEDO is the

reflectivity of the earths

surface. Darker colours

have a lower albedo; itabsorbs more incoming

radiation than lighter

colours.

In the photos, thesnowcapped mountains

have the highest albedo,

the forest the lowest. Ice

cover at the poles has a

high albedo, further

reducing temperature.

Albedo


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Aspect

North facing

South facing


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Unequal Radiation on a Sphere

Insolation > Terrestrial

Radiation

Insolation = Terrestrial

Radiation

Insolation < Terrestrial

Radiation

WINDS A 40 S i f i i i


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WINDS At 40N and S, there is a balance of insolation withoutgoing LW radiation over the year.

Insolation exceeds LW radiation in the daytime, and in

summer; the reverse is true at night and in winter.

Polewards of 40N and S, there is an annual heat

deficit, despite periods of surplus during some days and

in summer.

Equatorwards of 40N and S, there is an annual heat

surplus despite periods of deficit at night and in winter.

Without movement of heat energy, the poles would

become steadily colder and colder, while the equatorwould get progressively warmer. This clearly does not

happen.

This heat transfer (flux) occurs by:

Ocean currents; cold polar water flows towards theequator while warm water flows from equator to poles.

Winds which blow warm air towards the poles and

cold air towards the equator.


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Permanent Winds

OCEAN CURRENTS


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OCEAN CURRENTS

Cold Sea temperature Warm

Labrador current carries

cold water from equator to

pole down east coast of

N.America

Gulf Stream

carries warm

water from

equator towards

the pole, and NW

Europe


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Role of Vegetation

Vegetation changes daily and seasonally

Tropical Rainforest- Cool & Wet

Desert Vegetation- Hot & Dry

Deciduous Forest- Seasonal rainfall


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Humidity

Cools the air

Reduces temperature

Examples-

5N & 5 S Latitudes

Deserts


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Cloud Cover

Approximately 50% ofEarth is cloud covered atany given moment.

Clouds lower dailymaximum temperatures andraise nighttime minimumtemperatures.

D i l d


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Cloud Cover

At night,clouds act asinsulation andradiate

longwaveenergy,preventingrapid energyloss.

Daytime, clouds

reflect

insolation.


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Urbanization

GREENHOUSE EFFECT & OZONE


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The GREENHOUSE EFFECT, like a real greenhouse (below)

is to allow heat in, but not out. Gases in the atmosphere (CO2,

Methane) naturally trap outgoing LW radiation more

effectively than they do incoming SW radiation. This retains

heat, warming the earths atmosphere.

GREENHOUSE EFFECT & OZONE

DEPLETION

Ozone traps UV (SW)

radiation from

reaching the earthssurface. Human

pollutants (CFCs etc)

are destroying this

protective layer and

causing cancers of the

skin in Australia -

near the Antarctichole in the Ozone

layer.

THE ANTARCTIC

HOLE IN THE

OZONE LAYER

This has, over geological

time, been in balance.

Now, human activity is

increasing such gases so

the warming effect is

(possibly) beyond recall.

This is the modern

atmospheric temperature

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