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Weather and Climate

Global atmospheric circulation and the tricellular model

  • 3 things to know
  • Component 3 Section B

Overview

Three cells of the model in each hemisphere, circulation within the Hadley cell and circulation within the Polar cell.

What you need to know

Answer each one before you reveal it.

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Key term

What does the tricellular model describe?

Key term

Name the three cells of the tricellular model in each hemisphere

Key term

Between which latitudes does the Hadley cell operate?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What does the tricellular model describe?

    Model answer

    The tricellular model describes the three circulation cells that operate in each hemisphere between the equator and the pole. The model explains the global pattern of pressure and winds.

  2. 2

    Name the three cells of the model in each hemisphere.

    Model answer

    The three cells are the Hadley cell, the Ferrel cell and the Polar cell.

  3. 3

    Between which latitudes does the Hadley cell operate?

    Model answer

    The Hadley cell operates between the equator and roughly 30° of latitude.

  4. 4

    Describe the circulation within the Hadley cell.

    Model answer

    Intense heating at the equator lifts air, which cools and releases heavy rainfall. The air moves poleward aloft, sinks at about 30° and returns as the trade winds.

  5. 5

    Why is there low pressure at the equator?

    Model answer

    Strong surface heating causes air to rise, which reduces the mass of air pressing on the surface. The rising motion creates a belt of low pressure.

  6. 6

    Why is there high pressure at about 30° of latitude?

    Model answer

    Air that rose at the equator has cooled and lost its moisture, and it converges and sinks at around 30°. Descending air increases surface pressure.

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