Download - 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