Solar Energy, the Atmosphere and
Biomes
Earth-Sun Relationships
Earth’s Motions
• Earth has two principal motions—rotation and
revolution
Earth’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 Heat
Three mechanisms of energy transfer:
Conduction is the transfer of heat through matter
by molecular activity
Convection 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 Vary
Factors include:
• latitude
• heating of land and water,
• altitude
• geographic position
• cloud cover
• ocean currents
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.
Fig. 7-7, p. 145
Elevation
Mountain ice
and snow
Tundra (herbs,
lichens, mosses)
Coniferous
Forest
Deciduous
Forest
Tropical
Forest
Latitude
Tropical
Forest
Deciduous
Forest
Coniferous
Forest
Tundra Polar ice
(herbs,
and
lichens,
snow
mosses)
Stepped Art
Fig. 7-9, p. 147
Properties of Air
Density
• At constant pressure, warm is less dense than
cold air
• Therefore, warm air rises, cold air sinks
Properties of Air
Water Vapor Capacity
• Warm air has a higher capacity for water
• Specific humidity is a measure of the amount
of water vapor in the air
• Relative humidity is a ratio of the amount of
water present to the capacity
• If RH = 100%, saturation occurs
• Dew point is the temperature at which
saturation occurs
Properties of Air
Adiabatic Heating and Cooling
• As air rises in the atmosphere rises, P ↓, air
expands and cools
• As air sinks toward the surface, P ↑, air
volume ↓ and warms
Properties of Air
Latent Heat Release
• As the sun warms surface water, it absorbs
and stores energy as it evaporates
• As water vapor in the atmosphere condenses,
it releases this stored (latent) energy
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
LOW PRESSURE
Cool, dry
air
HIGH PRESSURE
Heat released radiates
to space
Condensation and
precipitation
Falls, is compressed, Rises, expands,
cools
warms
Hot,
wet air
Warm,
dry air
Flows toward low pressure, picks
up moisture and heat
HIGH PRESSURE Moist surface warmed
by sun
LOW PRESSURE
Fig. 7-4, p. 143
Global Winds & Biomes
Moist air rises, cools,
and releases moisture as
rain
Polar cap
Arctic tundra
Evergreen
60° coniferous forest
30°
Temperate deciduous
forest and grassland
Desert
Tropical deciduous forest
Equator
0° Tropical rain forest
Tropical deciduous forest
30°
Desert
Temperate deciduous
60° forest and grassland
Polar cap
Fig. 7-6, p. 144
Fig. 7-8, p. 146
Polar
Tundra
Subpolar
Temperate
Coniferous forest
Desert
Deciduous
forest
Grassland
Chaparral
Tropical
Desert
Rain forest
Tropical seasonal
forest
Savanna
Scrubland
Fig. 7-10, p. 147
Biomes
•
•
•
•
•
•
•
Tundra
Boreal forest
Temperate rainforest
Temperate seasonal forest
Woodland/shrubland
Tropical rainforest
Subtropical desert
CURRENTS
Fig. 7-2, p. 142
Thermohaline Circulation
Warm, less salty,
shallow current
Cold, salty, deep
current
Fig. 7-5, p. 143
El Nino Southern Oscillation
• 3 – 7 year cycle
• Surface currents in the tropical Pacific reverse
direction (trade winds weaken)
• Warm water moves westward, suppressing
the upwelling of nutrients off the coast of S.
America
• Fish populations are hurt
• Global impact: cooler, wetter conditions in SE
US; drier in S Africa, SE Asia
Biomes
For your biome PowerPoint:
• Describe vegetation and animal life
• Describe general climate; include global
location(s)
• Include a climate diagram (annual
temperature & rainfall)
• 3 – 5 slides; keep it simple!
Categorized by salinity, depth, water flow
AQUATIC BIOMES
Streams & Rivers
• Flowing fresh water
• Originate from springs or runoff
• Rapid flow = few producers; rely on terrestrial
biomes (leaves)
• Slow rivers: nutrients settle and provide
substrate for plants
• Rapids: high O2 content
Lakes and Ponds
• Contain standing water
• Divided into distinct zones:
• Littoral Zone: shallow area of soil & water
near shore; rooted plants, photosynthesis
• Limnetic Zone: rooted plants cannot survive;
phytoplankton photosynthesize
• Profundal Zone: deep lakes; low O2 due to
decomposers; muddy bottom: benthic zone