Atmospheric Circulation Atmospheric circulation results from the differential heating of the earth Heat is redistributed evenly over the globe Redistribution occurs via circulation of air in the atmosphere On a global scale, atmospheric circulation results from the differential heating of the planetary surface!! -more heat equator – less heat poles This situation is unstable and the heat must be redistributed more evenly over the globe!! Redistribution of heat occurs via circulation of air in the atmosphere and circulation of water in the oceans!!

Tropical Heating Greatest heating at the equator Hot air Rising air masses Development of low pressure zones Hot air Less dense Holds more moisture than cold air Moist air is less dense than dry air at the same temperature and pressure air with water vapor is less dense than dry air at the same temperature and pressure when heated, air expands and becomes less dense, warm air holds more moisture than cold air Net Effect - cold air is more dense than warm air, and cold, dry air is much more dense than warm, moist air!! greater heating at the equator (i.e., tropics) results in rising air masses and the development of low pressure zones

At altitudes with equivalent ambient temperatures (and densities) As air masses rise: Temperature decreases Water vapor cools and condenses Rain and heat is released At altitudes with equivalent ambient temperatures (and densities) Air masses spread laterally Move poleward and cool Cooling air masses descend at poles Creates high pressure Air moves from high to low pressure temperature decreases with altitude and water vapor in the rising air masses cools and condenses, resulting in rainfall and rainfall releases heat air masses continue to rise, eventually reaching altitudes with equivalent ambient temperatures and therefore densities, air masses spread laterally (i.e., north and south) at equivalent densities with the surrounding atmosphereair masses move poleward (either north or south of the equator) and cool cooling air masses ultimately begin to descend, creating high pressure zones

Hadley cell

Doldrums Trade winds Horse latitudes Prevailing westerlies Polar easterlies

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