Transcript Atmospheric Processes

The Sun
Mercury
Venus
Earth
The Moon
Mars
Phobos
Jupiter
Europa
Saturn
Titan
Uranus
Oberon
Neptune
Pluto
Order…
Atmospheric Processes
The structure of the atmosphere
The structure of the
atmosphere
•
8th June 1898 – French
scientist Léon Teisserenc de
Bort used balloons carrying
thermometers to record
temperature variations
within the atmosphere
•
Temperature decreased with
height to 11.8 km above sea
level (ASL), then remained
constant to 13 km ASL
•
206 further balloon ascents
over next 4 years showed
that temperature begins to
increase above 13 km ASL
•
Teisserenc De Bort had
discovered the stratosphere
Atmosphere can
be divided into
four layers:
Thermosphere
Mesosphere
Stratosphere
Troposphere
Layers reflect
differences in
ability to absorb
solar radiation
Atmospheric
pressure
•
Rapid fall in air density and
pressure with increasing
height above Earth’s surface
•
50% of atmospheric mass
lies within lowest 5.6 km
•
>99% of atmospheric mass
lies within lowest 40 km
•
Atmospheric pressure units
= millibars (mb or mbar)
•
Normal pressure at sea-level
= 1013.2 mb
Troposphere
•
Derived from the Greek word ‘tropos’
meaning ‘turn’ – referring to the layer’s
convective and mixing characteristics
•
Lowest layer of atmosphere – contains
75% of atmospheric mass
Pressure decreases with altitude
•
•
Approximately uniform decrease in
temperature with height of c.6.5°C per
1000 m – environmental lapse rate
•
Contains virtually all the atmosphere’s
water vapour, clouds and pollution
•
Contains the weather
Tropopause
Troposphere
Tropopause
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Temperature inversion that
acts as a ‘ceiling’ to air rising
within the troposphere
•
Latitudinal variations in height
of tropopause ASL:
– Equator = 16-18 km (11 miles)
– Poles = 8-9 km (5 miles)
•
Distortions in tropopause
occur above mid-latitude
jetstreams & tropical cyclones
– Dust and water vapour may
penetrate up into stratosphere
– Dry ozone-rich air drawn
down from stratosphere into
troposphere
Stratosphere
•
Derived from the Greek word ‘stratum’ meaning ‘layer’ – referring to
the layer’s stratified, non-convective nature
•
Located above troposphere – between c. 10 and 50 km (30 miles) ASL
•
Temperature increases with height from c. –60OC (lower stratosphere)
to c.0°C at c.50 km ASL (stratopause)
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Contains small amounts of ozone (Ozone Layer) – absorbs ultraviolet
(UV) solar radiation, causing warming of stratosphere
•
Extremely dry layer with no weather (stable conditions due to cold air
below)
•
Most meteorites entering the atmosphere burn out above the
stratosphere
Ozone Layer
• Discovered by Charles Fabry
and Henri Buisson, 1913
• From the Greek – “to smell”
• Absorbs 93-99% of the sun’s
UV light which could be
damaging to life on Earth
• Approximately 11-50 km in
altitude
• Approximately 90% of
Ozone in our atmosphere is
found here
• Created by the Ozoneoxygen cycle
Nacreous clouds
•
Also known as ‘mother of pearl’
or polar stratospheric clouds
•
Form at c.15-25 km (9-16 miles)
ASL during polar winter when
lower stratosphere
temperatures fall to c. –80OC
•
Consist of droplets / ice
crystals of water, nitric acid and
/ or sulphuric acid
•
Only visible before dawn / after
dusk as clouds receive sunlight
from below horizon and reflect
it to ground surface
Nacreous clouds
Nacreous clouds
Mesosphere
•
Derived from the Greek word ‘meso’ meaning ‘middle’
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Located above stratosphere – between c.50 and 85 km (50 miles) ASL
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Temperature again decreases with height from c.0OC (at stratopause)
to c.–90OC at c.80 km ASL (mesopause) (lowest value within layers)
There are no gases, particles or water vapour to absorb UV radiation
•
Thermosphere
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Derived from the Greek words ‘thermos’ meaning ‘heat’
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Located above mesosphere – between c.85 and 500 km ASL
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Temperature increases with height to c.1200OC at 350 km ASL – due
to oxygen molecules absorbing ultraviolet (UV) solar radiation
Ionosphere - upper mesosphere and
thermosphere (above 80km)
• Contains many ions (electrically charged particles)
• Absorbs UV radiation
• Can reflect radio signals
• Give rise to the northern and southern lights
There is no clearly defined boundary which marks the end
of the atmosphere – gases are continuously lost into space
(Exosphere) which is mainly made up of Helium and
Hydrogen
Noctilucent clouds
Noctilucent clouds
Noctilucent clouds
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Polar mesospheric clouds
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Form at c.85 km (50 miles) ASL
– highest clouds in atmosphere
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Formation not fully understood
– mainly composed of water ice
•
Most commonly observed
between 50O and 60O north
during summer months
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Only visible before dawn / after
dusk when lower atmosphere is
in Earth’s shadow – otherwise
too faint to be seen
•
First reported in 1885 – shortly
after eruption of Krakatoa
Aurora borealis
Aurora borealis
Fly through - NASA
• http://svs.gsfc.nasa.gov/vis/a010000/a01000
0/a010014/
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