ch4 - Ch. 4 The Atmospheric Circulation System The Global...

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Ch. 4 The Atmospheric Circulation System The Global Circulatory Subsystems Movement of air Over Earth’s surface because there are horizontal differences in pressure Vertically bc it is forced to rise mechanically due to changes in buoyancy : tendency of an object to float in a fluid; controlled by differences in density between the object and the fluid, where density is given by the mass of a substance within a unit volume Horizontal/vertical movements differences in temps on Earth Vertical movement As temp increases, so does pressure, molecules move faster Ex. In a balloon: air in balloon is less dense than air surrounding it, positively buoyant , rises o Balloon continues to rise until density of air outside matches inside, neutral buoyancy o Air in balloon is more dense than surrounding air, balloon will sink, negative buoyancy Heating surface below a parcel (column) of air parcel expands, density decreases parcel rises through air column Horizontal movement 2 adjacent columns of air, cooler column has greater density and higher pressure o air moves horizontally from region of higher-pressure cool air to the region of lower-pressure warmer air- air moves down the pressure gradient o atmospheric pressure is force f determined by mass m of air column and acceleration a due to gravity o pressure decreases as you rise up in atmosphere, at top – pressure reduces to 0 1. air moves from high pressure area to lower pressure area until 2 pressures are equalized. a. Air moves horizontally in lower troposphere from higher to lower pressure 2. Air mass is heated until its density is lower than that of its surroundings, the lower-density air will rise – convection a. Subsidence: air mass is cooled until its density is higher than that of the underlying air, sinks The Driving Force: The Global Energy Distribution
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ch4 - Ch. 4 The Atmospheric Circulation System The Global...

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