MET4300_SWX_LEC11

MET4300_SWX_LEC11 - MET 4300 Lecture 11 Air Masses &...

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MET 4300 Lecture 11 Air Masses & Fronts
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Airmasses An airmass is a large body of air with relatively uniform thermal and moisture characteristics. Airmasses cover large regions of the earth, typically several hundred thousand square kilometers. Airmasses can be as deep as the depth of the troposphere or as shallow as 1 to 2 km. Airmasses form when air remains over a relatively flat region of the earth* with homogeneous surface characteristics for an extended period of time. (* Canadian and Siberian plains, cool oceanic regions such as the North Atlantic and Pacific, deserts, such as the Sahara and the American southwest, and tropical oceanic regions including the equatorial Atlantic and Pacific, and smaller water bodies such as the Caribbean Sea and the Gulf of Mexico).
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Sources of North American Airmasses Continental Arctic (cA): Ice cap or frozen sea Continental Polar (cP): High-latitude land mass Maritime Polar (mP): High-latitude sea Maritime Tropical (mT): Tropical (Trade-Wind) sea Continental tropical (cT): Desert Air-Mass Modification takes place outside source region North American weather is dominated by alternation of cP and mT air
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Key features of an airmass on weather maps : The centers of cold airmasses are associated with high pressure on surface weather maps. High pressure develops in response to cooling.
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In winter, high-pressure centers form and are the dominant feature over the northern parts of the continents of Asia and North America.
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Example of a high pressure system that moved southward into the central US in winter
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In summer, when the oceans are cooler than the landmasses, large high- pressure centers are the dominant feature of the atmosphere over the North Atlantic and Pacific Oceans. The high-pressure center over
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This note was uploaded on 02/18/2012 for the course MET 4300 taught by Professor Staff during the Spring '08 term at FIU.

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MET4300_SWX_LEC11 - MET 4300 Lecture 11 Air Masses &...

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