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Why do we have thunderstorms in the afternoon on
many summer days in Gainesville? |
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The pressure decreases with altitude. |
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Warm air expands and cold air contracts. |
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The pressure above the warm air is thus higher
than above the colder air for a given altitude. |
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There is a force and wind from the warmer to
colder air. |
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As air flows, the air above the colder region
becomes further compressed. |
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This creates a high pressure near the surface. |
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A surface wind blows from cold to warm regions. |
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During the day, the water heats less than the
land. |
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The air above the water is cooler and the air
blows from water to land. |
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Rising air over land creates clouds. |
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Because of the sea breeze, air blows from the
east on the east coast and from the west on the west coast. |
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The converging and rising air creates clouds and
rain. |
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Because of sea (lake) breezes, the temperature
tends to be cooler on the coast and warmer inland during the summer. |
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At night the air cools more than the water. |
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The wind blows from land to sea. |
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Clouds created by rising air form over the
water. |
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In the winter a large shallow high pressure area
develops over Siberia, producing clockwise flowing air that goes to the
Indian Ocean and South China Sea. |
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Monsoon wind system = changes direction
seasonally. |
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In the summer air over the continents becomes
much warmer and air flows in from the water, creating rain and the wet
season. |
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During the day sunlight warms the valley walls. |
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The warm air rises producing a valley breeze and
frequently clouds. |
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The process reverses at night (mountain breeze). |
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Strong downhill winds result when air flows from
a high plateau (cold, high pressure) to a valley (warmer, low). |
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Examples: bora (Yugoslavia), mistral (France),
Columbia Gorge wind (US). |
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As wind blows from the West over the Rocky
Mountains it looses its moisture and warms creating the warm dry Chinook
wind on the eastern slope. |
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The warming is due to latent heat and
compression. |
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Air descends from elevated desert plateau,
funneling through mountain canyons, into LA basin and San Fernanodo Valley. |
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Air warms through compression, carries dust and
sand, and dries out vegetation. |
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Cold downdrafts along leading edge of a
thunderstorm lift dust and sand. (Shown: Pheonix, Arizona). |
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Warm rising air is twisted by wind blowing past
an obstacle leading to a dust devil, whirlwind, or willy-willy. |
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Different from tornado where air descends. |
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Texas norther – intense winter storm goes east
across the Great Plains through Texas. Temperatures may drop 10o
in a few hours. |
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Northeasters – storm develops off of east coast
and moves north east along the coast.
They usual bring heavy winds and snow. |
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Thermal circulations created by uneven
heating/cooling over land and water create sea breezes, afternoon showers
in Florida, and the monsoon in India and Asia. |
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Wind flowing over or down mountains create
valley breezes, katabatic winds, the Chinook wind, and the Santa Ana wind. |
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