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air pressure

the air exerted by the weight of air above

all directions

in which direction is air pressure exerted?

exactly balances it

What does the air pressure pushing down on an object do to the air pressure pushing up on the object?

barometer

the instrument the measures atmospheric pressure

millibar

the unit scientists use to measure atmospheric pressure

1013.2 millibars

standard sea-level pressure

aneroid barometer

uses a metal chamber with some air removed

variations in air pressure

what is an aneroid barometer extremely sensitive to?

wind

the result of horizontal differences in air pressure

unequal heating of Earth's surface

what generates pressure differences that generate winds?

solar radiation

what is the ultimate energy source for most wind?

pressure gradient

The difference in atmospheric pressure between areas of higher pressure and lower pressure.

isobars

lines of equal pressure on a weather map

a steep pressure gradient and high winds

what do closely spaced isobars indicate?

a weak pressure gradient and light winds

what do widely spaced isobars indicate?

anticyclones

air moves clockwise away from the center

highs/anticyclones

pressure increases from the outside toward the center

lows/cyclones

pressure decreases from the outer isobars toward the center

cyclones

air moves counterclockwise toward the center

cloud formation and precipitation

what is rising air associated with?

low

in what type of pressure areas does the air rise?

clear skies

what does sinking air produce?

high

in what type of pressure area is the air sinking?

Polar Easterlies, Westerlies, and Trade Winds

the atmosphere is divided into these 3 main wind belts

heating from the sun

what causes air at the equator to rise?

the warm air that rose at the equator cools as it moves north and south and descends at 30 degrees. as it descends it warms and dries out

Why do desserts tend to be located at 30 degrees North and South?

at the equator, calm winds

where are the Doldrums located?

trade winds

two belts that blow almost constantly from easterly directions at 30 degrees north and south to the equator. early sailing ships used these winds to sail by

sea breeze

starts developing shortly before noon and generally reaches its greatest intensity during mid- to late afternoon

sea breeze

these relatively cool winds can be a moderating influence on afternoon temperatures in coastal areas

land breeze

the opposite of a sea breeze. they influence the evening temperatures in coastal areas

land breeze

the cooler air over the land moves to the sea, where the air is warmer and at lower pressures

valley breeze

this is created because warmer air on mountain slopes is less dense and it rises up along the slope

mountain breeze

air along the mountain slopes cools and air moves down slope into the valley. air in the valley is still warmer and rises and is replaced by the cooler air

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