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8.11: The Coriolis Effect on Atmospheric and Ocean Circulation Systems

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    The Coriolis Effect on Atmospheric and Ocean Circulation Systems

    Heat from insolation (short for INcoming SOLar radiATION) is the driving force behind the fluid motion of the atmosphere and the oceans. However, the patterns of motion are also influenced by the forces created by the rotation of the Earth on its axis. Any mass moving in a rotating system experiences a force (the Coriolis force) the acts perpendicular to the direction of motion and to the axis of rotation. Because air has mass, air currents maintain momentum when moving from a location of high pressure to low pressure. However, because the Earth is rotating, the rotation causes a right-turn deflection in the Northern Hemisphere and a left-turn deflection in the Southern Hemisphere (Figure 8.29).

    Coriolis Effect
    Figure 8.29. The Coriolis effect is cause by the rotation of the Earth on its axis. This rotation causes air masses moving from high to low pressure to deflect.

    The Coriolis effect influences all moving objects, especially ones moving over large distances (such as intercontinental ballistic missiles). The Coriolis effect causes objects or moving masses of air to:
    • Change direction—not speed.
    • Maximum Coriolis effect occurs at poles.
    • No Coriolis effect occurs at equator.

    Rotation of pressure systems due to the Coriolis effect:

    Northern Hemisphere:
    • High pressure turns clockwise
    • Low pressure turns counter-clockwise

    Southern Hemisphere: opposite of N.H.
    • High pressure turns counter-clockwise
    • Low pressure turns clockwise

    Coriolis effect video (NOVA PBS)

    So... which way does the water spin in a toilet in the northern hemisphere, southern hemisphere, and on the equator?

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