What Causes Wind?

1
What Causes Wind?

• Differences in air pressure

2
What is Wind?

• The horizontal movement of air from an area of
  high pressure to an area of low pressure

3
An Anemometer measures wind speed

• The increased cooling that a a wind can cause is
  called a wind-chill factor.
• Makes it feel colder than the actual temperature

4
LOCAL WINDS

• Winds that blow over short distances
• Always caused by unequal heating of Earths
  surface within a small area
• Only form when no winds are blowing from farther
  away

5
Sea Breeze Flow of air from an ocean or lake
onto land During the day, the air over land
becomes warmer than the air over the waterwarm
air expands and rises, creating a low-pressure
area. So, cool air blows inland from the water
and moves beneath the warm air.
6
Land Breeze flow of air from land to a body of
water

• At night, it reverses and land cools more quickly
  than water, so the air over land becomes cooler
  than the air over waterso, warm air over the
  water rises and is replaced by cooler air from
  the land.

7
Monsoons

• Sea and land breezes over a large region that
  change direction with the seasons
• Summer monsoon important for crops in South Asia

8
Global Winds

• Winds that flow steadily from specific directions
  over long distances
• Created by unequal heating of the Earths surface

9
Global Convection Currents

• Produced by the movement of air between the
  equator and the poles caused by temperature
  differences
• So, air pressure is lower toward the equator and
  higher toward the poles

10
The Coriolis Effect

• Because earth rotates, global winds do not travel
  in a straight line
• The way Earths rotation makes winds curve is
  Coriolis Effect
• In the Northern Hemisphere, winds gradually turn
  rightopposite in the southern hemisphere

11
Global Wind Belts

• Trade winds Equator to 30 north and south
  (N-from NE, S-from SE)
• Horse Latitudes At 30N and S, Belt of calm air
  forms, Air stops moving towards poles and sinks
• Doldrums near the equator, sun heats surface
  strongly, warm air rises, cool air replaces, but
  is warmed rapidly and it rises.little
  horizontal movement, little or no wind

12

• Prevailing Westerlies blow from the west
  between 30 and 60 N and S of the equator
• Polar Easterlies At 60 N and S, from the east

13
Jet Stream

• About 10 km above earths surface
• High-speed winds
• Blow from west to east
• Wander N and S along a wavy path
• When planes fly east, save fuel and time by
  flying in a jet stream