1. Solar Energy, the Atmosphere and Biomes

2. 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

4. 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

6. 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)

7. 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

8. 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

10. What Happens to Solar Radiation?
Why Temperatures Vary
Factors include:
latitude
heating of land and water,
altitude
geographic position
cloud cover
ocean currents

13. 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.
Figure 7.7
The rain shadow effect is a reduction of rainfall and loss of moisture from the landscape on the side of a mountain facing away from prevailing surface winds. Warm, moist air in onshore winds loses most of its moisture as rain and snow on the windward slopes of a mountain range. This leads to semiarid and arid conditions on the leeward side of the mountain range and the land beyond. The Mojave Desert in the U.S. state of California and Asia’s Gobi Desert are both produced by this effect.
Fig. 7-7, p. 145

14. Tundra (herbs, lichens, mosses)
Elevation
Mountain ice and snow
Tundra (herbs, lichens, mosses)
Coniferous Forest
Deciduous Forest
Tropical Forest
Latitude
Tropical Forest
Deciduous Forest
Coniferous Forest
Tundra (herbs, lichens, mosses)
Polar ice and snow
Figure 7.9
Generalized effects of elevation (left) and latitude (right) on climate and biomes. Parallel changes in vegetation type occur when we travel from the equator to the poles or from lowlands to mountaintops. Question: How might the components of the left diagram change as the earth warms during this century? Explain.
Stepped Art
Fig. 7-9, p. 147

15. Properties of Air Density
At constant pressure, warm is less dense than cold air
Therefore, warm air rises, cold air sinks

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

24. 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 ( km/hour); little friction

25. 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

26. Heat released radiates to space Condensation and precipitation
LOW PRESSURE
HIGH PRESSURE
Heat released radiates to space
Condensation and precipitation
Cool, dry air
Falls, is compressed, warms
Rises, expands, cools
Warm, dry air
Hot, wet air
Figure 7.4
Energy transfer by convection in the atmosphere. Convection occurs when hot and wet warm air rises, cools, and releases heat and moisture as precipitation (right side). Then the denser cool, dry air sinks, gets warmer, and picks up moisture as it flows across the earth’s surface to begin the cycle again.
Flows toward low pressure, picks up moisture and heat
HIGH PRESSURE
LOW PRESSURE
Moist surface warmed by sun
Fig. 7-4, p. 143

27. Global Winds & Biomes

29. Moist air rises, cools, and releases moisture as rain
Polar cap
Arctic tundra
Evergreen coniferous forest
60°
Temperate deciduous forest and grassland
Desert
30°
Tropical deciduous forest
Equator 0°
Tropical rain forest
Tropical deciduous forest
30°
Desert
Figure 7.6
Global air circulation, ocean currents, and biomes. Heat and moisture are distributed over the earth’s surface via six giant convection cells (like the one in Figure 7-4) at different latitudes. The resulting uneven distribution of heat and moisture over the planet’s surface leads to the forests, grasslands, and deserts that make up the earth’s terrestrial biomes.
Temperate deciduous forest and grassland
60°
Polar cap
Fig. 7-6, p. 144

30. Figure 7.8
Natural capital: the earth’s major biomes—the main types of natural vegetation in various undisturbed land areas—result primarily from differences in climate. Each biome contains many ecosystems whose communities have adapted to differences in climate, soil, and other environmental factors. Figure 5 on p. S27 in Supplement 4 shows the major biomes of North America. Human activities have removed or altered much of the natural vegetation in some areas for farming, livestock grazing, lumber and fuelwood, mining, and construction of towns and cities (see Figure 3, pp. S24–S25, and Figure 7, pp. S28–S29, in Supplement 4). See an animation based on this figure at CengageNOW. Question: If you factor out human influences such as farming and urban areas, what kind of biome do you live in?
Fig. 7-8, p. 146

31. Decreasing temperature Decreasing precipitation
Cold
Polar
Tundra
Subpolar
Temperate
Coniferous forest
Decreasing temperature
Desert
Deciduous forest
Grassland
Tropical
Chaparral
Hot
Figure 7.10
Natural capital: average precipitation and average temperature, acting together as limiting factors over a long time, help to determine the type of desert, grassland, or forest biome in a particular area. Although each actual situation is much more complex, this simplified diagram explains how climate helps to determine the types and amounts of natural vegetation found in an area left undisturbed by human activities. (Used by permission of Macmillan Publishing Company, from Derek Elsom, The Earth, New York: Macmillan, Copyright © 1992 by Marshall Editions Developments Limited).
Desert
Wet
Rain forest
Savanna
Dry
Tropical seasonal forest
Scrubland
Decreasing precipitation
Fig. 7-10, p. 147

32. Biomes Tundra Boreal forest Temperate rainforest
Temperate seasonal forest
Woodland/shrubland
Tropical rainforest
Subtropical desert

33. Currents

34. Figure 7.2
Natural capital: generalized map of the earth’s current climate zones, showing the major contributing ocean currents and drifts and upwelling areas (where currents bring nutrients from the ocean bottom to the surface). Winds play an important role in distributing heat and moisture in the atmosphere, which leads to such climate zones. Winds also cause currents that help distribute heat throughout the world’s oceans. See an animation based on this figure at CengageNOW™. Question: Based on this map what is the general type of climate where you live?
Fig. 7-2, p. 142

35. Thermohaline Circulation
Warm, less salty, shallow current
Figure 7.5
Connected deep and shallow ocean currents. A connected loop of shallow and deep ocean currents transports warm and cool water to various parts of the earth. This loop, which rises in some areas and falls in others, results when ocean water in the North Atlantic near Iceland is dense enough (because of its salt content and cold temperature) to sink to the ocean bottom, flow southward, and then move eastward to well up in the warmer Pacific. A shallower return current aided by winds then brings warmer, less salty—and thus less dense—water to the Atlantic. This water can cool and sink to begin this extremely slow cycle again. Question: How do you think this loop affects the climates of the coastal areas around it?
Cold, salty, deep current
Fig. 7-5, p. 143

36. 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

38. 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!

40. Categorized by salinity, depth, water flow
Aquatic biomes

41. 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

42. 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