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8.4: Density of Air

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    10265
    • Contributed by Miracosta Oceanography 101
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    Density of Warm Air vs. Cool Air

    As air is heated it expands (moving atoms apart). This reduces the density of air in unconfined space. As a result warm air rises. Conversely, as air cools, it condenses (moving atoms together) and increases it's density in unconfined space. As a result cold air sinks. Because the atmosphere is unconfined, dense cool air will sink and flow to displace warm air in another location (Figure 8.12).

    Hot air and cold air
    Figure 8.12. Differences in air pressure at different levels in the atmosphere drive the movement of air.

    Density of Moist Air vs. Dry Air

    Air saturated with water vapor is less dense than dry air. As a result, moist air will rise relative to dry air if air temperatures and pressures are the same.

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