Download Circulation Cells - Hadley

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Circulation Cells
Heating of the Earth’s surface and atmosphere by the sun drives convection within the atmosphere and oceans,
producing winds and ocean currents. Air circulating via convection cells and acted upon by the Coriolis force
redistribute that heat energy. These patterns create bands of warmer, wetter regions and bands of cooler, drier
regions at specific latitudes. This pattern creates a diversity of conditions for life and results in the existence of
different biomes (major ecosystems) on the planet.
Convection Cell Circulation
1. Draw and label 2 Hadley convection cells
Hot air rises from the equator (red arrow), spreads north and loses heat eventually sinking (blue arrow)
when it reaches the 300 latitude and cycles back toward the equator. A second Hadley cell rises at the
equator, spreads south, sinks at the south 300 latitude and cycles back to the equator.
2. Draw and label 2 Ferrel convection cells
Sinking air at the 300 northern latitude splits and some of it moves northward instead of cycling back to the
equator (blue arrow). It picks up heat as it moves across the surface and eventually is hot enough to rise
when it reaches the 600 latitude (red arrow). Label this the Ferrel cell. A second Ferrel cell sinks at the 300
southern latitude (blue arrow) and rises at the 600 latitude (red arrow).
3. Draw and label 2 Polar convection cells
Earth’s coldest air from the 900 pole sinks along the land (blue arrow) and warms as it moves along the
surface. By the time it reaches the 600 latitude it has absorbed enough heat and rises (red arrow) and cycles
back to the pole. Label it the Polar cell. Draw a second polar cell for the south pole with air sinking at 900
(blue arrow) moving toward the equator and rising at the 600 (red arrow).
4. Label Atmospheric Pressure Zones
Rising air has Low pressure. There are 4 low pressure zones label each.
Dropping air has High pressure. There are 3 high pressure zones label each.
5. Draw and label the Trade Winds.
The bottom of each convection cell produces surface winds that is curved due to the spin of the Earth called
the Coriolis effect. Air in the northern hemisphere is curved toward the right and in the southern
hemisphere is curved toward the left. Draw an arrow for each Hadley cell that goes from 300 toward the
equator but is curved toward the west. Label them the Trade winds.
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6. Draw and label the Westerlies
Wind is often named for the direction it originates; so the westerlies start in the west and move east.
The wind in the Ferrel cell area moves along the surface from 300 to 600 but is curved toward the east.
Draw and label this wind the Westerlies.
7. Draw and label the Polar Easterlies
The wind in the Polar cell moved from the pole to the 900 but is curved toward the west. Draw and
label the Polar Easterlies.
8. Distribution of Biomes
Biomes are large ecosystems that are characterized by their temperature and rainfall. These are distributed
on the earth based on convection cell locations.
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Rainforests are hot and wet and found between 200 north and 200 south latitudes. Shade the land areas
within these latitudes light green.
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Deserts are hot and dry and found at 25-350 north and south. Shade them brown.
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Forests are cold and wet found between 45- 570 north and south latitudes. Shade dark green.
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Tundras are cold and dry found north of 600 north latitude. Shade yellow
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Create a Key to show which color relates to which biome.
Follow-up questions:
1. What parts of the Earth are the hottest? Why?
2. What is a convection cell? What causes convection cells to start?
3. Draw one convection cell with 4 arrows. Label the hot air, cold air, more dense air, less dense air and
the surface air that would become wind.
4. How many convection cells are there on the Northern hemisphere? What are they called and what is the
latitude area of each?
5. When air is rising what happens to the temperature? To the pressure? To the climate?
6. When air is sinking what happens to the temperature? To the pressure? To the climate?
7. On Earth, what latitudes have high pressure? What direction is the air moving there? What is the
climate like there?
8. On Earth, what latitudes have low pressure? What direction is the air moving there? What is the
climate like there?