Lecture10_Atm_CircI-1 - EAS 1600 Introduction to...

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EAS 1600 Introduction to Environmental Sciences Class10- General Circulation of the Atmosphere In this class we discuss the general circulation of the atmosphere and its role in redistributing the energy that was unevenly deposited on the Earth by the absorption of solar energy. It is sometimes said that the atmosphere is one massive heat engine driven by solar radiation and that weather is simply the manifestation of the heat engine’s work. Today we find out why . .. But first a few definitions: General circulation: The long-term average winds (directions and speed) in the atmosphere as a function of location. By long- term,we usually mean on decadal time scales. Climate: The long-term average state of the atmosphere. Weather: The instantaneous state of the atmosphere and its short-term variability. Sensible heat: The energy contained in molecules as a result of their random kinetic energy (or motion). In other words the energy you can feel as heat. Thermal conduction: The transfer of sensible heat through materials or gases that are in contact as a result of the collision of hot molecules with cool molecules. Note no transfer of mass is required. Thermal convection and advection: The transfer of sensible heat by the movement (or exchange) of mass. Convection usually refers to vertical movement and advection to horizontal movement. Our motivation: Recall: The energy budget of solar and planetary radiation is in balance in total, but not as a function of latitude.
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The imbalance requires energy flow from tropics to poles… One possible way for the atmosphere to accomplish this is through its General Circulation. If winds carry warm air pole-ward and cool air to the tropics (on average), there will be a net flow of energy (as sensible heat) like that illustrated above. Let’s see how. .. Air, like all bodies, are subject to the Laws of Motion. ¾ Things at rest will tend to remain at rest. ¾ To move an object at rest or change the speed or direction of an object, a force must be applied. F = ma So the movement of air requires a force. In general there are two forces available:
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Lecture10_Atm_CircI-1 - EAS 1600 Introduction to...

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