Transcript The Atmosphere

Earth’s Atmosphere
And Weather
Atmosphere Intro
Flying
Paragliding
Composition of the Atmosphere
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78% nitrogen: little effect on weather
21% oxygen: component necessary for human life
Argon: 3rd most abundant gas; no effect on weather
Carbon dioxide: very tiny amount; absorbs energy so it
is significant in heating the atmosphere
• Water vapor: amount varies from 0 – 4%; it is the
source of all clouds and precipitation; absorbs heat
• Ozone: O3 ; located in the ozone layer in the
stratosphere; blocks UV radiation
• dust
Comparison of Earth’s diameter to the thickness of the
atmosphere
• The diameter is 12734.9km and the
atmosphere is approximately 100 km.
Layers of the Atmosphere
Layers of the atmosphere
• Troposphere: lowest layer; as altitude
increases temperature decreases; where
weather is located
• Stratosphere: jet stream; airplanes fly here; as
altitude increases temperature increases;
ozone layer Global Solar Index Guide
• Mesosphere: meteoroids, as altitude increases
temperature decreases
• Thermosphere: satellites orbit here; aurora
borealis; as altitude increases temperature
increases
Earth's Magnetic Field
• Plane ride through the atmosphere
Earth’s Rotation and Revolution
• Earth revolves around the sun once every
365 days.
• Earth rotates on its axis once every 24
hours.
• Earth is tilted on its axis.
Temperature and heat
• Temperature is a measure of the average
kinetic energy of the particles of an object
• Heat transfer is the movement of thermal
energy from a warmer object to a cooler
one
• Three methods of heat transfer: conduction,
convection, radiation
Conduction
• Heat is transferred through conduction when
particles collide and pass movement onto or
increase movement in other particles.
Convection
• Heat transfer through the movement of a fluid
(something that flows – gases as well as
liquids)
Radiation
• Transfer of heat through electromagnetic
waves (infrared are specifically felt as heat)
Density
• The concept of density is very important when
considering heat.
• As objects are heated they become less dense –
there are less particles in a given space
because the heated material expands
Specific Heat
• The amount of heat needed to raise the
temperature of one gram of material by one
degree Celsius
• For this class it is more important to
understand that some materials (land – think
about how hot sand gets in the sun) heat up
and cool off faster than others and this impacts
temperature and weather
Factors that affect temperature
• Land and water: land heats and cools
quicker than water; so proximity to water
moderates temperature
Factors that affect temperature
• Latitude – distance from the equator
Windward (upwind) locations less range in
temp.; leeward (downwind) locations more
range in temp.
Altitude: higher – cooler; lower – warmer
Geographic position affects temperature
Cloud cover and albedo
• Albedo is the fraction of total radiation that
is reflected by any surface.
• Many clouds have a high albedo so they
reflect much of the sunlight that strikes
them back into space.
Affects of cloud cover
• In the day clouds reduce incoming solar radiation and have
a cooling effect.
• At night clouds absorb
radiation from the land
and reradiate it back to
Earth increasing nighttime
temperatures.
Air pressure
measured with a
barometer
air pressure
-is the
pressure
exerted by
the weight
of air above
Exerted in
all
directions
Horizontal differences
cause wind
H
L
wind
Isobars connect places
(on a weather map) of
equal pressure. Spacing
of isobars indicates
amount of pressure
change.
Pressure Centers
• Centers of low pressure or cyclones
1. Pressure decreases from outer isobars inward
2. Winds blow inward and counterclockwise
3. Bring rainy weather
Pressure Centers
• Centers of high pressure or anticyclones
1. Pressure increase from outer isobars inward
2. Winds blow outward and clockwise
3. Bring sunny weather
Wind
Wind is caused by
differences in air
pressure.
L
H
Unequal heating of
earth’s surface causes
air pressure differences
– the heating is from
solar radiation
Pressure differences –
greater difference in
pressure greater the
wind speed
wind
The Corealis Effect
Friction between the
Above the friction layer
deflects the wind to the air and the earth’s
- the jet stream (120 –
right
surface slows wind and 240 km/hr)
changes its direction
Wind
Speed is measured
using a anemometer.
Wind is named for the
direction the wind
comes from.
Wind direction is
indicated by a wind
vane.
Sea Breeze
H
L
breeze
Land Breeze
L
H
breeze
Atmospheric water – changes in state
sublimation
melting
solid
vaporization
liquid
freezing
gas
condensation
deposition
• Humidity – amount of water vapor in air
• Saturation – holding as much moisture as it
can
• Relative humidity – ratio of actual water
vapor content to amount of water vapor air
could hold at that temperature and pressure
– sling psychrometer
• Dew point - temperature to which air must
cool to reach saturation
Cloud Formation
• Adiabatic temperature changes – no
addition or subtraction of heat
• Occur when air expands (it cools) and when
it compresses (it warms)
• As a parcel of air rises high enough it will
cool to dew point and condensation will
begin
• Condensation nuclei – surface for water
vapor to condense on
Processes that lift air
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•
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Orographic
Frontal wedging
Convergence
Localized convective
Orographic Lifting
Frontal Wedging
Convergence
Localized Convective Lifting
Air Masses
• A large body of air with similar temperature
and moisture
• m – maritime : indicates
a moist airmass that forms
over water
• c – continental: indicates
a dry air mass that forms
over land
• P - polar: indicate a cold
air mass
• T – tropical: indicates a
warm air mass
• A – arctic: bitter cold air
mass
Fronts
• Boundaries separating air masses
– Include cold fronts, warm fronts, occluded
fronts and stationary fronts
Cold Front
• Boundary where a cold air mass
is entering an area of warm air
• Symbol blue line with triangles
pointing toward the warm air
• Brings strong heavy rain and possible violent
storms
• Temperature – warmer ahead of front, cooler after
front passes
• Clouds: ahead of front- cirrus, stratocirrus, and
cumulonimbus; at front – cumulonimbus; behind
front - cumulus
Warm Front
• when a warm air mass
overrides a cold air mass
• Symbol – solid red line
With semicircles pointing
toward the cold air
• Brings light to moderate rain, sleet or snow
Occluded front
• When a cold front catches
up with a warm front
• Symbol – a solid line with
alternating triangles and semicircles pointing in the
direction the front is moving
• Brings light, moderate or heavy continuous rain
Stationary
• Occurs when a warm front
Or cold front stops moving
• Symbol – solid line with alternating
triangles and semicircles; triangles point
toward the warm air and the semicircles
point toward the cold air
• Brings long periods of precipitation
• http://www.youtube.com/watch?v=huKYKykjc
m0
Mid-latitude cyclones
https://www.youtube.com/watch?v=ZUaOP677NlI