When a parcel of air is allowed to expand, it_____?
cools
Why does a parcel of air expand as it rises upward through the atmosphere?
Air pressure decreases as you go up, allowing air to expand and cool.
Air pressure is the pressure exerted by the _____ of air above a certain point.
weight
Why doesn't the weight of air above a table crush it?
The air pressure pushing down exactly balances the air pushing up.
barometer
measures air pressure
When air pressure increases, the mercury in the tube of a mercury barometer_____.
rises
_____is caused by horizontal differences in air pressure.
wind
What three factors combine to control wind?
pressure differences, the coriolis effect, and friction
How are isobars related to pressure gradients?
the spacing between them indicates the change in pressure or pressure gradient.
Due to the Coriolis effect, winds in the Northern Hemisphere are deflected to the___?
right
How does friction effect wind?
it slows air movement, which changes wind direction.
___ _____ are high-altitude fast-moving rivers of air that travel from west to east.
jet streams
How do pressure differences affect wind?
as pressure increases, wind increases
Cyclones are centers of ____ pressure associated with clouds and precipitation.
low
In the Southern Hemisphere, winds around a cyclone flow _____.
outward
Why do weather reporters always emphasize cyclones and anticyclones?
so they can predict bad weather
In which wind zone does sinking dry air produce deserts in some areas?
trade winds
What causes monsoons?
seasonal changes/a shift in wind direction
What is a polar front?
when the polar easterlies collide with the westerlies (creating a stormy boundary)
Cyclones have...?
a low pressure center and inward winds
Anticyclones have...?
a high pressure center and outward winds
In the Northern Hemisphere, low pressure = _____-_____ ____, and high pressure = _____ _____.
counter-clockwise winds; clockwise winds
In the Southern Hemisphere, low pressure = _____ _____, and high pressure = ____-_____ ____.
clockwise winds; counter-clockwise winds
How does friction affect the flow of cyclones and anticyclones?
in cyclones it causes air to flow inward around low pressure; in an anticyclone it causes air to flow outward around high pressure
Weather around a low pressure center can be expected to be_____.
bad
Weather around a high pressure center can be expected to be______.
good
_____ _____ are small-scale winds produced by a locally generated pressure gradient.
local winds
List two causes of local winds...
1) topographic effects 2) variations in surface composition in the immediate area
Land Breeze
At night, air over land cools and moves out over water.
Valley Breeze
during the day, heated air along mountain slopes rises.
Sea Breeze
During the day, heated air over land rises, allowing cooler air to move in from over water.
Mountain Breeze
At night, cooled air along mountain slopes moves downward.
What is a prevailing wind?
it occurs when wind blows more constantly from one direction than from any other.
Anemometer
measure wind speed
El Nino
an episode of ocean warming that affects the eastern tropical pacific.
El Nino episodes occure at irregular intervals of __ to __ years.
3 to 7
What conditions trigger a La Nina episode?
surface temp. and weather patterns such as trade winds
How are rain forests related to wind paterns?
how much rain they get is affected by the trade winds and their convergence.