Download Global Wind Patterns - ms. Clayton`s 7th grade Science

Global Wind Patterns
Remember…
• When we talked about air pressure we said
that cold air sinks and warm air rises. This
movement causes air to move.
Key Vocabulary:
• Weather – the condition of Earth’s
atmosphere at a specific time and place.
• Wind – the air that moves horizontally or
parallel to the ground.
• Meteorologist – a person who studies the
weather.
How Wind Forms
1. Sunlight strongly heats an area of the ground.
The warm air rises and low pressure forms.
2. Sunlight heats an area of the ground less
strongly. The cooler air sinks and high
pressure forms.
3. Air moves as wind across the surface from
higher to lower pressure.
How far does wind travel?
• The distance wind travels varies.
• Some wind die out after traveling only a few
meters.
• Global Winds travel thousands of kilometers
in steady patterns and can last for weeks.
Earth’s Rotation Affects Wind Direction
• Because Earth rotates, scientists are able to
tell the directions wind will flow.
• The Coriolis Effect is the influence of Earth’s
rotation on wind patterns.
• Global winds curve as the Earth turns beneath
them. Winds in the northern hemisphere
curve right and winds in the southern
hemisphere curve left.
Global Wind Patterns
• The Earth’s rotation and the uneven heating of
its surface cause a pattern of wind belts
separated by calm regions.
Global Wind Patterns – Calm Regions
• The Doldrums – low pressure zone near the
equator. Warm air rises and spreads out
toward the poles.
• The horse latitudes – high pressure zones
located at 30 degrees north and 30 degrees
south. Warm air traveling away from the
equator cools and sinks in these regions.
Global Wind Patterns – Wind Belts
• The trade winds – blow from the east moving from
the horse latitudes toward the equator. These
winds die out as they near the equator.
• The Westerlies – blow from the west, moving from
the horse latitudes toward the poles.
• The Easterlies – blow from the east, moving from
the polar region toward the mid-latitudes. Stormy
weather often occurs when the cold air of the
easterlies meets the warm air of the westerlies.
Doldrums
Horse
Latitude
Jet Streams
• Not all wind occurs near Earth’s surface.
• Jet streams flow in the upper troposphere
from west to east for thousands of kilometers.
• Air in jet streams often moves at speeds
greater than 200 km per hour.
• Just like other global winds jet streams form
because of the uneven heating of Earth’s
surface.
• Each hemisphere has two jet streams, a polar
jet stream and a subtropical jet stream.
How Does Wind Affect Travel
• Before the invention of steam engines sailors
used sails to capture the wind and take them
across the ocean.
• Name one area that sailors would have disliked.
Why?
• Today jet streams affect air travel. They can
make flights shorter or longer.
• Think of one example where a flight might be
shortened because of a jet stream.