Meteorology 5.01 Heating and Cooling of the Atmosphere References: FTGU pages 123, 124, 136 and 137.
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Transcript of Meteorology 5.01 Heating and Cooling of the Atmosphere References: FTGU pages 123, 124, 136 and 137.
Meteorology
5.01 Heating and Cooling of the AtmosphereReferences:
FTGU pages 123, 124, 136 and 137
5.01 Heating and Coolingof the Atmosphere
• MTPs:– Vertical Structure– Composition– ICAO Standard Atmosphere– Temperature Scales– Atmospheric Properties– Atmospheric Density– Temperature Differences– Heating and Cooling
Vertical Structure
• Troposphere– Weather happens here– To 25,000 – 30,000
feet over poles– To 55,000 – 65,000
feet over equator– Temperature
decreases with height• Stratosphere
– Troposphere to 170,000’
– Temperature increases with height
Vertical Structure
• Mesosphere– Stratosphere to 270,000’– Temperature decreases
with height, to -85°C• Thermosphere
– Tops at 1.1 million to 2.6 million feet (350-800 kilometres)
– Temperature increases with height, up to 1,500°C
• Exosphere– Mainly comprised of
hydrogen and helium– Extends into space
Vertical Structure
Vertical Structure
• Label the layers of the atmosphere!
• Choose from these:– Stratosphere– Thermosphere– Exosphere– Troposphere– Mesosphere
Composition
• The atmosphere is made up of a mixture of gases– Nitrogen (78%)– Oxygen (21%)
– Other (~1%) (Argon, CO2, Water Vapour etc.)– Although water vapour is less than
1% of the atmosphere, it remains
the most important component
from the standpoint of weather,
based especially on its ability to
change state
Nitrogen
Oxygen
Other
ICAO Standard Atmosphere
• The International Civil Aviation Organization (ICAO) Standard Atmosphere:– Sea Level for North America– Based on summer and winter averages at
40°N latitude• The Standard:
– MSL pressure of 29.92” Hg (1013.25 hpa)– MSL temperature of 15°C– Air is a “perfectly dry gas”– Lapse rate of 1.98°C per 1000 feet
Temperature
• Sun heats earth, earth heats atmosphere• Celsius (nearly worldwide):
– Freezing point of water: 0°C– Boiling point of water: 100°C
Atmospheric Properties
• Mobility– The ability for air to move– Atmosphere like an “ocean of air”– Wind like “streams of water”– (Much more freedom of movement with air than water)
• Compression– Air is compressed as it descends into greater
pressure– Occupies less space
Atmospheric Properties
• Expansion– As air rises, it reaches areas of lower
pressure, causing it expand and cool– This cooling can be enough to condense
water vapour in the air, forming cloud– This is why clouds and precipitation are
common in areas of rising air– From a meteorological standpoint, the
most important property of the air!
– www.youtube.com/watch?v=Li9eyds1Y_g
Atmospheric Properties
Density - mass per unit volume• Cold air is dense:
– Molecules are move slowly and are packed close together– Heavier and tends to sink
• Warm is less dense:– Molecules are moving rapidly taking up more space (or less molecules in the same space)– Warm air is lighter and is pushed up by the cold air
Atmospheric Density
• Density Relationships:–Density vs. Temperature:
• Indirectly proportional
–Density vs. Humidity:• Indirectly proportional
–Density vs. Pressure:• Directly proportional
Confirmation
• Questions • 1. What is the most important property of the
atmosphere?
• 2. If the density of the air increases, what happens to the pressure?
• 3. What gas makes up the majority of the atmosphere?– Nitrogen 78%
Temperature Differences
• Horizontal Temperature Differences– Diurnal Variation– Seasonal Variation – earth’s tilt– Latitude- north pole versus equator– Topography
• Land and water differences– Clouds
• Clouds reflect large amounts of solar radiation
• At night, clouds trap the heat radiated off the earth
Atmosphere Heating
• Types of Atmospheric Heating:
– Radiation (heating)• Earth absorbs
sun’s short wave radiation
• The lower atmosphere is then heated by the earth
66
LONG & SHORT WAVELONG & SHORT WAVE’’SS
SHORT WAVEINSOLATION
LONG WAVETERRESTRIALRADIATION
Atmospheric Heating
– Conduction• If two substances are
in contact, heat will flow from the warmer to the colder substance
• Air is a poor conductor, so this usually only occurs in small layers
• Same as the heat transferred when roasting marshmallows
Air warmed by conductionAir warmed by conduction
Cool airCool air
Cold airCold air
Solar radiationSolar radiation
warm surfacewarm surface
Atmospheric Heating
– Convection• Air heated
through conduction becomes buoyant and rises
• This air then heats the air in the upper atmosphere
99
COLD AIR
COLD AIR
COLD AIR
mixing
occurs
warmwarmairair
risesrises
heat is carriedheat is carriedverticallyvertically
by convectionby convection
WARM SURFACEWARM SURFACE
Convection
Atmospheric Heating
– Advection (heating)
• Occurs when cold air moves over a warm surface and its lower layer is heated by conduction
advectiveadvectivewarmingwarming
COLDCOLD WARMWARM
WARM SURFACEWARM SURFACE
Advection
Atmospheric Heating
– Turbulent Mixing• Turbulent air
mixes a warmer surface layer of air with an unheated air aloft, spreading the heat upward
1111
TURBULENT MIXINGTURBULENT MIXING
WIND CAUSES WIND CAUSES TURBULENCE TURBULENCE
MIXES LOW MIXES LOW LEVEL HEAT TO LEVEL HEAT TO UPPER LEVELSUPPER LEVELS
Cool air
warm surface
warm air
Turbulentmixing
Atmospheric Heating
–Compression• As air descends it compresses due to increased pressure and therefore heats up
CompressionSinking Air iscompressed byhigher pressure and its temperature will increase
Atmospheric Cooling
– Advection cooling• Lower levels only• When air is cooled
by moving over a colder surface
• Cooling occurs as a result of conduction between air and surface
• Some mechanical turbulence can aid in spreading cooling effect
Advection CoolingAdvection Cooling
cool surface
COLDCOLD
WARMWARM
advective cooling
Warm Air moving Over a cooler surface
Atmospheric Cooling
– Expansion cooling• The most
important cooling process of the air
• Air forced to rise experiences lower pressure and is allowed to expand
• This expansion causes decrease in temperature
WARMWARM
Lower pressure Lower pressureCOOL
AIREXPANDS
&COOLS
Expansion Cooling
Confirmation
Questions1. Name 2 types of atmospheric heating
2. Name 2 types of atmospheric cooling
3. Describe how the earth is heated and cooled through radiation.
4. Which layer of the atmosphere contains all weather?
Soaring