Our atmosphere is perilously thin. Yet it provides important solar protection as well as oxygen.
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Transcript of Our atmosphere is perilously thin. Yet it provides important solar protection as well as oxygen.
Our atmosphere is perilously thin.
Yet it provides important solar protection as well as oxygen.
Components of Earth’s Atmosphere
78% Nitrogen21% Oxygen~1% Trace gases
CO2
H2OArgonMethane
Trace gases are critical because they regulate temperatures on Earth.
Other Components:
• AerosolsTiny, 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
• Closest to Earth • Thinnest/densest layer• Convection• Where weather occurs
—water vapor and clouds
• Temperature decreases with altitude
—6°C per kilometer
Troposphere
• Above troposphere to 50 km above surface
• Ozone layer—Absorbs harmful UV
radiation
• Temperature increases because of ozone absorption of UV radiation.
Stratosphere:
Other layers:
Mesosphere
Thermosphere
IonosphereAurora Borealis
ExosphereThe 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-Conduction-Convection
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 EnergyVariation 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 CharacteristicsWarm 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.