the pressure exerted by the weight of air
How is air pressure exerted?
in all directions
the air pressure pushing down on an object exactly balances________
the air pressure pushing up on the object
What is a barometer?
a device used for measuring air pressure
How does a barometer measure air pressure?
when air pressure increases, the mercury in the tube rises. When air pressure decreases, so does the height of the mercury column
What three factors combine to control wind?
pressure differences, the Coriolis effect, and friction.
what two terms have to do with pressure differences?
pressure gradient and isobars.
What is a pressure gradient?
the amount of pressure change occurring over a given distance.
What are isobars?
lines on a map that connect places of equal air pressure.
What do they indicate?
they indicate a steep pressure gradient and high winds.
Widely spaced isobars indicate_______
a weak pressure gradient and light winds.
Isobars where the air pressure number is the highest in the middle show______
Isobars that have the lowest air pressure number in the middle show_______
What is the Coriolis Effect
the Coriolis effect describes how Earth's rotation affects moving objects.
What happens in the northern hemisphere in the Coriolis Effect?
all free-moving objects or fluids are deflected to the right of their path of motion
and the southern hemisphere?
all free-moving objects or fluids are deflected to the left of their path of motion.
What is friction?
friction acts to slow air movement, which changes air direction.
What are jet streams?
fast moving "rivers of air
Jet streams travel in a ____ to _____ direction
east to west
Jet streams travel between ___ and ___ ____
120 and 240 kmph
What are cyclones?
centers of low pressure
What are anticyclones?
centers of high pressure
When the pressure gradient and the Coriolis effect are applied to pressure centers in the Northern Hemisphere_______
winds blow counterclockwise around a cyclone and clockwise around an anticyclone.
What happens in the southern hemisphere?
winds blow counterclockwise around an anticyclone and clockwise around a cyclone
In either hemisphere, friction causes a netflow of air inward around a(n)_____ and a net flow of air outward around a(n)______
1. cyclone 2. anticyclone
What is rising air associated with?
cloud formation and precipitation (rain, snow, sleet, hail, etc)
What is sinking air associated with?
Low-Pressure centers (cyclones) produce_____
bad weather in any season
High-Pressure centers (anticyclones) produce____
nice (fair) weather in any season
What is the Non-Rotating earth model?
On a hypothetical non-rotating planet with a smooth surface of either all land or all water, two large thermally produced cells would form.
What are two important things to remember about the non-rotating earth model?
1. It is HYPOTHETICAL!!! 2. the earth would need to be made of ALL land or ALL water.
What is the problem with the non-rotating earth model
some areas would be freezing because of no sunlight and other areas would receive too much sunlight.
Name the 4 global wind types
trade winds, westerlies, easterlies, polar fronts
What is a polar front?
a stormy frontal zone separating cold air masses of polar origin from warm air masses of tropical origin.
What is a monsoon?
the seasonal reversal of wind direction associated especially with Asia.
In the winter, the wind blows from ____ to ___
land to sea
In the summer, the sea blows from ___ to ____
sea to land
What are local winds?
winds that are caused either by topographic effects (mountains, valleys, etc.) or by variations in surface composition (land and water) in the local area
What are land and sea breezes like in the day?
in coastal areas during the warm summer month, in the day the air moves from high pressure to low pressure. The high pressure is the water and the low pressure is the land. So in the day, wind moves from sea to land.
What are land and sea breezes like in the night?
the land cools faster than the water at night so the air moves to the warm water making the wind blow from land to sea at night.
What are valley and mountain breezes?
the air on the slopes of the mountain is heated more intensely than the air at the same elevation but at the valley floor. The air on the slopes is less dense so it glides up the slope and generates a valley breeze. The pattern may reverse after sunset.
What are prevailing winds?
winds that blow more often from one direction than from any other.
What is an anemometer?
an instrument that resembles a cup and is commonly used to measure wind speed.
What is El Niño?
the periodic warming of the ocean
Where does El Niño occur?
in the central and eastern Pacific
What happens at irregular intervals of three to seven years?
the warm countercurrents become unusually strong and replace normally cold offshore waters with warm equatorial waters.
What can a major El Niño cause?
Extreme weather in many parts of the world and the loss of many fish.
What is La Niña?
the name for when the temps. in the eastern pacific are colder than average.
La Niña has___
a distinctive set of weather patterns.