Transcript Understanding Our Environment

Air, Weather, and Climate
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Earth’s Atmosphere
Compared to the size of the Earth (12000 km),
the atmosphere is a thin shell (120 km)
Composed of:
– ~78% N2 gas
– 21% O2 gas
– 1% argon gas and other permanent gases
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If the Earth is
compared to
this Orange…
the Earth’s
atmosphere
would be
thinner than
the layer of
pesticide on
this Orange’s
surface
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Layers of the Atmosphere
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Troposphere
Stratosphere
Mesosphere
Thermosphere
Ionosphere
Exosphere
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Troposphere
 Closest to the earth’s surface
 Where we live
– Weather occurs here
 very thin (averaging 11 km or 7 miles high)
 Contains 75% of mass most from water vapor
 Temp decreases as altitude increases
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Stratosphere
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Above the troposphere
extends to 50 kilometers (31 miles) high
dry and less dense
Warmer temps higher up and cooler layers
farther down, due to the absorption of uv rays
 Ozone layer
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Mesosphere
 extends to 85 kilometers (53 miles) high
 extremely low air pressure
 temperature decrease with altitude reaching
-90°C at the top
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Thermosphere
 extends to 600 kilometers (372 miles) high
 temperatures go up as altitude increases due to
absorption of solar radiation by oxygen
 molecules so few and far between that they
collide rarely
 Farthest away from earth’s surface
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Ionosphere
 when solar energy is absorbed directly by air
molecules, the atoms gain or lose electrons and
become charged particles called ions
 reflects many types of radio waves allowing
them to bounce around the world
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Exosphere
 Top of the thermosphere and continues until it
merges with interplanetary gases, or space (372
to 6200 miles)
 H and He are the primary components
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Weather
 Contribute to Weather
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Air temperature
Air pressure
Humidity
Cloud cover
Precipitation
Winds
 Types of Weather
– Fronts
– Severe Weather
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Air Temperature
 As solar energy reaches the equator, regions heat
up more than the poles.
 Warm air and water at the equator travel toward
the poles while cold air and water at the poles
travel toward the equator in an attempt to
equalize the temperature
– Constant struggle = changing weather
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http://www.usatoday.com/weather/tg/wglobale/wglobale.htm
Air Pressure
 Caused by the weight of air pressing down on the Earth
 High pressure-cool, dense air that descends towards
surface of earth
– Fair weather
 Low pressure-less dense warm air goes toward the
center of a low pressure air mass
– Produces cloudy and stormy weather
 Air pressure changes with weather
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Humidity and Cloud Cover
 Relative humidity-amount of water vapor in the air
 Cloud Cover
– clouds cool the planet by reflecting sunlight back
into space.
 Albedo
– reduces the amount of heat that radiates into space
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Winds
 Horizontal wind moves from areas of high to
low pressure
 Vertical wind moves from low to high pressure
 Speed is determined by differences in pressure
 Coriolis effect
– As air moves from high to low pressure in the N.
hemisphere, it is deflected to the right
– Opposite for S. hemisphere
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Winds cont.
 Hadley cells
– Carries heat and moisture from the tropics to the
northern and southern mid-latitudes
 Rising air motion near the equator
 Descending air motion in the subtropics
– Lost most of water vapor
– Where deserts are located
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Convection Currents
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Weather
 Weather – daily temperature and moisture
conditions in a place
– driven by atmosphere
– atmospheric conditions over short time periods (hours
or days) in small geographic areas
– produced by interacting air masses
– Types of weather
 Warm Front-warm air displaces cool air
 Cold Front-cooler air displaces warmer air
 Severe-hurricanes, thunderstorms, tornadoes
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Climate
 Climate – long term weather patterns
– driven by atmosphere
– Uneven heating of earth’s surface
 Equator
 Seasonal changes in temp and precip
 Opposite seasons in N&S hemispheres
– determines distribution of biomes across Earth
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What Factors Control Climate?
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Latitude
Elevation/topography
Nearby water
Ocean currents
Vegetation
Prevailing winds
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Ocean Currents
 Warm/cold currents influence land climate
 Currents redistribute heat from sun which influences climate
– El Nino – change in the direction of tropical winds warms SA
and NA coastal surface waters, suppresses upwellings, and
alters weather
 Warm water spreads from the west Pacific to the east
Pacific
 Effects
– Distorts jet stream
– Reduces primary productivity
 Some fish species decline
– La Nina -cooling counterpart
 Upwelling of nutrient rich water
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“Natural” Greenhouse Effect
 Solar radiation passes through the atmosphere.
– ~51% of the sun's radiation reaches the surface
 This energy is then used in number of processes including:
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heating of the ground surface
melting of ice and snow
evaporation of water
plant photosynthesis
– ~30% is reflected back to space by clouds and the surface
– ~19% of the energy available is absorbed by clouds and gases
 Gases absorb and reradiate this outgoing radiation, effectively storing
some of the heat in the atmosphere, thus producing a net warming of
the surface
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“Natural” Greenhouse Effect cont.
 This process has kept the Earth's temperature
about 60 degrees Fahrenheit warmer than it
would otherwise be.
 Life on Earth could not be sustained without the
natural greenhouse effect.
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