solar energy and the atmosphere. earth-sun relationships earth’s motions earth has two principal...
TRANSCRIPT
Solar Energy and the Atmosphere
Earth-Sun Relationships
Earth’s Motions• Earth has two principal motions—rotation and
revolutionEarth’s Orientation (tilt)• Seasonal changes occur because Earth’s
position relative to the sun continually changes as it travels along its orbit
Energy Transfer as HeatThree mechanisms of energy transfer:Conduction is the transfer of heat through matter
by molecular activityConvection is the transfer of heat by circulation
within a substance.Radiation is the transfer of energy (heat) through
space by electromagnetic waves that travel out in all directions
What Happens to Solar Radiation?
• Scattering:–Clouds, dust and gas reflect and bend light
rays; light rays are sent out in all directions–Causes sky to appear blue (blue light is more
easily bent)– Sunsets appear red because longer
wavelengths (red) are able to reach the surface (we are looking through more atmosphere on the horizon)
What Happens to Solar Radiation?
• Reflection:–20% of solar radiation is absorbed by the
atmosphere–50% is absorbed by the surface–30% is reflected back into space–Albedo: fraction of solar radiation that is
reflected back into space. – Earth’s albedo is 0.3
What Happens to Solar Radiation?
Absorption & Infrared Energy:• As the surface absorbs radiation, it heats up and
releases IR radiation• IR radiation is trapped by water vapor and CO2 in
the atmosphere• This process is called the greenhouse effect
What Happens to Solar Radiation?
Why Temperatures VaryFactors include:• latitude • heating of land and water, • altitude• geographic position• cloud cover• ocean currents
Fig. 7-7, p. 145
Prevailing winds pick up moisture from an ocean.
On the windward side of a mountain range, air rises, cools, and releases moisture.
On the leeward side of the mountain range, air descends, warms, and releases little moisture.
Latitude
Tropical Forest
Deciduous Forest
Coniferous Forest
Tundra (herbs, lichens, mosses)
Polar ice and
snow
Fig. 7-9, p. 147
ElevationMountain ice and snowTundra (herbs, lichens, mosses)Coniferous Forest
Deciduous ForestTropical Forest
Stepped Art
Factors Affecting Wind
• Wind is the result of horizontal differences in air pressure. Air flows from areas of higher pressure to areas of lower pressure
• The unequal heating of Earth’s surface generates pressure differences
• Three factors combine to control wind: pressure differences, the Coriolis effect, and friction
Factors Affecting Wind
Pressure Differences• A pressure gradient is the amount of pressure
change occurring over a given distance• Isobars are lines on a map that connect places
of equal air pressure• Closely spaced isobars indicate a steep pressure
gradient and high winds
Factors Affecting Wind
Coriolis Effect• The Coriolis effect describes how Earth’s
rotation affects moving objects. • In the Northern Hemisphere, all free-moving
objects or fluids, including the wind, are deflected to the right of their path of motion.
• In the Southern Hemisphere, they are deflected to the left
Factors Affecting Wind
Friction • Friction acts to slow air movement, which
changes wind direction• Jet streams are fast-moving rivers of air that
travel in a west-to-east direction (120 - 240 km/hour); little friction
Global Winds
• Convection Cells:–Warm air rises near the equator–Cooler air from the north replaces it at the
surface–The warm air that rose flows northward
and downward as it cools–The convection cells are called Hadley Cells
Fig. 7-4, p. 143
Heat released radiates to spaceCool, dry
air
Condensation and precipitation
Falls, is compressed, warms
Rises, expands, cools
Warm, dry air
Hot, wet air
Flows toward low pressure, picks up moisture and heat
HIGH PRESSURE Moist surface warmed by sun
LOW PRESSURE
LOW PRESSURE HIGH PRESSURE
Global Winds
Fig. 7-6, p. 144
Moist air rises, cools, and releases moisture as rainPolar cap
Arctic tundraEvergreen coniferous forest60°
Temperate deciduous forest and grassland
30°Desert
Tropical deciduous forest
Equator 0° Tropical rain forest
30° Desert
60°Temperate deciduous forest and grassland
Tropical deciduous forest
Polar cap
Fig. 7-8, p. 146
Fig. 7-10, p. 147
Cold Polar
TundraSubpolar
TemperateConiferous forest
Desert
Deciduous forest
GrasslandChaparral Tropical
Hot
DesertWet Rain forest Savanna
Tropical seasonal forest
Dry
Scrubland
Trade Winds• Winds that blow out of the east between 0-
30° latitude
Westerlies• Winds out of the west; between 30-60°
Polar Easterlies• Winds out of the east; from 60-90°
Global Winds
The Doldrums:• Equatorial “Low”• Little or no winds“Horse” Latitudes:• 30° latitude: sub-tropical high• Little or no winds
CURRENTS
Fig. 7-5, p. 143
Warm, less salty, shallow current
Cold, salty, deep current
Fig. 7-2, p. 142