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Weather and Climate

Global atmospheric and oceanic circulation

  • 3 things to know
  • A2 Unit 4

Overview

Three cells of the tricellular model, operation of the Hadley cell and polar cell.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

Name the three cells of the tricellular model.

Key term

Describe the operation of the Hadley cell.

Key term

Explain why deserts cluster around 30° north and south.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Name the three cells of the tricellular model.

    Model answer

    The Hadley cell, the Ferrel cell and the Polar cell.

  2. 2

    Describe the operation of the Hadley cell.

    Model answer

    Intense heating at the equator makes air rise, it moves polewards aloft, cools and descends at around 30°, then returns to the equator as the trade winds.

  3. 3

    Where is the intertropical convergence zone, and what happens there?

    Model answer

    It is the belt near the equator where the trade winds of both hemispheres meet, forcing air to rise and producing heavy convectional rainfall.

  4. 4

    Explain why deserts cluster around 30° north and south.

    Model answer

    Air descending in the subtropical high pressure belt warms and dries as it sinks, so cloud cannot form and rainfall is very low.

  5. 5

    Describe the Polar cell.

    Model answer

    Cold dense air sinks at the pole, flows towards lower latitudes at the surface as the polar easterlies, and rises again at around 60°.

  6. 6

    What is the polar front?

    Model answer

    The polar front is the boundary at around 60° where warm tropical air meets cold polar air and is forced to rise, generating depressions.

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