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Earth Science
Grade 9-12
Atmospheric Circulation Cells Reference Cheat Sheet
A printable reference covering Hadley, Ferrel, and Polar cells, pressure belts, prevailing winds, Coriolis effect, and ITCZ for grades 9-12.
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Atmospheric circulation cells describe how air moves in large loops from the equator to the poles. This topic explains why Earth has global wind belts, deserts near 30 degrees latitude, and stormy zones near 60 degrees latitude. Students need this cheat sheet to connect heating, pressure, rotation, and climate patterns in one clear reference. It is especially useful for interpreting weather maps, climate zones, and ocean current patterns.
Key Facts
- Unequal solar heating causes warm air to rise near the equator and cold air to sink near the poles.
- The Hadley cell extends from 0 degrees to about 30 degrees latitude, with rising air near the equator and sinking air near 30 degrees.
- The Ferrel cell extends from about 30 degrees to 60 degrees latitude and is an indirect cell driven by neighboring Hadley and Polar cells.
- The Polar cell extends from about 60 degrees to 90 degrees latitude, with rising air near 60 degrees and sinking cold air near the poles.
- The Coriolis effect deflects moving air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
- Surface winds flow from high pressure toward low pressure, but Earth’s rotation curves their path into prevailing wind belts.
- Major surface wind belts are trade winds from 0 degrees to 30 degrees, westerlies from 30 degrees to 60 degrees, and polar easterlies from 60 degrees to 90 degrees.
- The pressure pattern by latitude is low at 0 degrees, high at 30 degrees, low at 60 degrees, and high at 90 degrees.
Vocabulary
- Hadley Cell
- A large circulation loop between the equator and about 30 degrees latitude where warm air rises and then sinks in the subtropics.
- Ferrel Cell
- A midlatitude circulation loop between about 30 degrees and 60 degrees latitude that helps produce the prevailing westerlies.
- Polar Cell
- A high-latitude circulation loop between about 60 degrees and 90 degrees latitude where cold dense air sinks at the poles.
- Coriolis Effect
- The apparent curving of moving air or water caused by Earth’s rotation.
- Intertropical Convergence Zone
- A low-pressure belt near the equator where trade winds meet, warm air rises, and frequent clouds and storms form.
- Prevailing Winds
- Winds that usually blow from a consistent direction over a large region because of global circulation and the Coriolis effect.
Common Mistakes to Avoid
- Reversing high and low pressure belts is wrong because rising air creates lower surface pressure, while sinking air creates higher surface pressure.
- Forgetting the Coriolis direction leads to incorrect wind belts because air curves right in the Northern Hemisphere and left in the Southern Hemisphere.
- Thinking circulation cells are perfectly fixed is wrong because the belts shift north and south with the seasons as the Sun’s direct rays move.
- Calling all winds from west to east trade winds is wrong because trade winds blow generally from east to west, while westerlies blow generally from west to east.
- Ignoring latitude causes incorrect cell identification because Hadley, Ferrel, and Polar cells are defined by their approximate latitude ranges.
Practice Questions
- 1 At 30 degrees north latitude, is air generally rising or sinking, and what type of surface pressure usually forms there?
- 2 A city is located at 45 degrees south latitude. Which circulation cell is it in, and which prevailing wind belt affects it most?
- 3 List the pressure belts from the equator to the North Pole using high or low pressure at 0 degrees, 30 degrees, 60 degrees, and 90 degrees.
- 4 Explain why many large deserts are found near 30 degrees north and 30 degrees south latitude.