Transcript Chapter Opener

Our
atmosphere
is perilously
thin.
Yet it provides
important
solar
protection as
well as
oxygen.
Components of Earth’s
Atmosphere
78% Nitrogen
21% Oxygen
~1% Trace gases
CO2
H 2O
Argon
Methane
Trace gases are critical because they
regulate temperatures on Earth.
Other Components:
•
Aerosols
Tiny, microscopic
particles of solids
that stay
suspended in the
air
Fine dust, volcanic
ash, sea salt,
pollen, etc.
Important because:
– Act as
condensation
nuclei for
raindrops to
form.
– Can absorb or
reflect solar
radiation.
Other Components:
Ozone
03 molecules
– Absorb ultraviolet
(UV) rays
Critical in stratosphere
Pollutant in troposphere
Layers of Earth’s Atmosphere
Earth’s atmosphere is divided into layers,
each with different characteristics:
• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Ionosphere
• Exosphere
Troposphere
•
•
•
•
Closest to Earth
Thinnest/densest layer
Convection
Where weather occurs
—water vapor and clouds
• Temperature decreases
with altitude
—6°C per kilometer
Stratosphere:
• Above troposphere to
50 km above surface
• Ozone layer
—Absorbs harmful UV
radiation
• Temperature increases
because of ozone
absorption of UV
radiation.
Other layers:
Mesosphere
Thermosphere
Ionosphere
Aurora Borealis
Exosphere
The average temperature
of Earth’s atmosphere
varies in a zig-zag pattern
with altitude.
Solar radiation- electromagnetic energy
emitted by the Sun.
• Visible, short-wavelength radiation
Terrestrial radiation is reemitted solar
radiation from Earth’s surface.
• Infrared, longer-wavelength radiation
Radiation-ConductionConvection
The Sun sends
ultraviolet and
visible light to Earth
by radiation.
Infrared (heat) is
produced at the
surface and warms
Earth’s atmosphere
by conduction.
Convection works in
the atmosphere.
Solar Energy
Solar intensity is highest
where the Sun’s rays strike
Earth’s surface straight on.
• Flashlight beam at 90°
angle to the surface
• Equatorial regions
Solar intensity is weaker
where the Sun’s rays strike
Earth’s surface at an angle.
• Flashlight beam at an
angle
• Higher latitudes
The Sun’s
rays don’t
strike all
places on the
Earth with the
same
intensity.
Solar Energy
Variation in solar intensity with latitude helps to
explain the different climates.
Seasons
When the Sun’s rays are closest to
perpendicular at any spot on the Earth,
that region’s season is summer.
Six months later, as the rays fall upon the
same region more obliquely, the season is
winter.
In between are the seasons fall and spring.
Air Pressure
Atmospheric pressure
= force the
atmosphere exerts
on an area of
surface.
Force = weight of air
molecules above
that surface.
Air Pressure
• At any level in the
atmosphere, force
= total weight of
air above that
level.
• At higher
elevations, fewer
air molecules
above—
atmospheric
pressure is less.
Air Characteristics
Warm air:
• Expanded-lower density
and lower pressure
• Rises due to density
differences
Cool air:
• Contracts-higher density
and higher pressure
• Sinks due to density
differences
This process is called
convection and drives
the weather
What is the wind?
Wind is air that flows
horizontally from
higher pressure to
lower pressure.
What causes the wind?
Pressure differences (gradient) - caused by
uneven heating of the Earth’s surface.
The greater the pressure gradient, the
stronger the wind.
Water has a high specific heat.
It takes a long time to warm up but a long
time to cool down again.
This contributes to the pressure differences.
Coriolis Effect
Earth’s rotation greatly affects the
path of moving air.
• Moving bodies (such as air) deflect
to the right in the Northern
Hemisphere, to the left in the
Southern Hemisphere.
• Deflection of wind varies according
to speed and latitude.
— Faster wind, greater deflection
— Deflection greatest at poles,
decreases to zero at equator
Global Wind Circulation
Patterns
The atmosphere is
divided into circulation
cells.
This results from:
unequal heating of
Earth’s surface and
Earth’s
rotation.
Latitudes have different
characteristics due to circulation
cells.
Equator- low pressure, clouds form, rainy
climate. Low winds (doldrums)
• Rainforests
30° N and S- high pressure, dry air (horse
latitudes)
• Deserts
60° N and S- low pressure, cool, dry air meets
warm, moist air— (Polar Front)
Wind Patterns
Equator to 30°N and S
• Trade winds- strong winds that blow
westward (0°–)
30° to 60 ° N and S
• Westerlies –winds blow eastward
60°– 90° N and S
• Polar easterlies-winds blow westward
There are 5 major gyres in the
ocean.
Each gyre is powered by both the trade
winds and the westerlies.