WIND
 Is air in motion
 Is caused by the uneven heating of the earth’s surface by the sun
 Warm air which weighs less than cold air, rises. Cool air moves in and
replaces the rising warm air
Cold Air
Warm Air
 High pressures are cool air; low pressures are warm air
 Winds blow from a high pressure to a low pressure
 Winds are named from the direction they blow from
DIFFERENT TYPES OF WIND PATTERNS
1. JET STREAM: narrow belts of strong winds found in the lower stratosphere
2. GLOBAL WIND PATTERNS: These are winds that are happening in the upper
atmosphere ALL THE TIME. These patterns are made because hot air (low
pressure) rises and cold air (high pressure) sinks.
Tradewinds—0-30 degrees latitude
 at the equator (0 degrees), air rises, and then sinks at around
30 degrees north and south
Westerlies—30-60 degrees latitude
 Air sinks at 30 degrees north and south and rises again at 60
degrees north and south
 Are responsible for moving weather across the U.S.
Polar Easterlies—60-90 degrees latitude
 Air rises at 60 degrees north
and south, and then sinks at the
poles
Doldrums
 are found at the equator and
are weak winds.
Horse Latitudes
 Found at about the 30° latitude
over the oceans…weak winds
here
3. LOCAL BREEZES: occur because of the heating differences of land and water
SEA BREEZES—a convection current blows wind from
the cooler sea towards warmer land during the day
Land warms up faster than water during the day
Wind blows from a high to a low (cold to warm)
Sea Breeze
LAND BREEZES occur at night, air moves toward the
water as the land cools more rapidly than the water.
Water keeps its heat longer than land at night
Land Breeze
Winds are named by the direction they blow
from
AMAZING EARTH SCIENCE FACTS
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Winds are caused by the uneven heating of the earth
Coriolis Effect causes deflections of air masses and ocean currents due to the rotation of the
Earth
Winds blow from high pressure to low pressure
Cold air is high pressure because the molecules are close together and weight more than hot
air
Warm air is low pressure because the molecules are far apart, therefore weight less
U.S. weather is dominated by prevailing westerlies. Weather moves west to east.
Sea breeze- daytime, land is hot (low) ocean is cold (high) winds blow high to low
Land breeze-occurs at night and is the exact opposite of the conditions above