1. Understand the cause of wind and how it affects climate
WINDS
Understand the cause of wind and how it affects climate
Chapter 4
Pages 59-67

2. What is Wind? A wind is a horizontal movement of air across a surface.
Vertical movements are currents or updrafts and downdrafts
Caused by what????
Heat versus cold!! Relate it to convection cells previously studied!!!

3. What causes wind? Unequal heating!
Unequal heating causes pressure differences .
Cold, heavy air sinks = high pressure
Warm, expanding air rises = low pressure
Winds blow from high (cold) to low (warm)
Anyone got a light????

5. Know that air blows from areas of high pressure to areas of low pressure.
The statement is fact.
Real examples:
Air inside a balloon
Exhaling
Air powered pellet gun
It is simply fact.
High and low pressures in the earth’s atmosphere are responsible for wind P

6. Application - Land Breeze
Using your knowledge of wind predict & explain the wind direction below. P. 61
FACT: Water holds heat longer than the land.
At night, sea air is warmer than air over the land.
Air rises over sea
Relative Low pressure over sea
Cold land air moves to lower pressure
Low Pressure

7. Land Breeze
Night time
Cool breeze
Off the land

8. Application - Sea Breeze
Using your knowledge of wind predict & explain the wind direction below. P. 61
FACT: Land heats up faster than the water
During the day, air over the land is warmer than air over the sea
Air rises over land
Relative Low pressure over land
Sea air moves to lower pressure
Cold “Breeze” off the ocean during the day
Low Pressure

9. Sea Breeze
Day time
Cool Breeze
Off the ocean

10. Define the terms wind & prevailing wind. p.61-63
is a horizontal movement of air across a surface.
It results from air masses of different temperatures and humidity lying next to each other.
The resulting pressure variation causes “wind” to blow from high pressure areas to low pressure areas.
Prevailing Wind:
Is regular, predictable, normal wind direction for a given area or region.
Caused by global convection cells.
Named after the direction from which it comes

11. Prevailing Winds Lab

12. Prevailing
Winds

13. Describe how the coriolis force affects wind direction.
objects in motion tend to deflect
to the right in north hemisphere
to the left in south hemisphere
Due to the earth’s rotation
Consequently winds:
in the northern hemisphere tend to curve to the right of their path.
while in the southern hemisphere they deflect left of their path.

14. Summary of prevailing wind
Global highs and lows are due to uneven heating of the earth
Air moves from high pressure to low pressure creating winds
Winds are deflected in the directions indicated on the diagram due to the coriolis effect.

15. Make inferences about how winds are related to major pressure belts. p
Air rises at the equator
It settles at the poles
Result = 6 convection cells
3 above and 3 below the equator.
Low pressures result where hot air rises.
High pressures result where air settles

16. Describe Orographic (Relief) rainfall p. 66
Leeward
Chinook
Windward
A relatively warm, moist air blows off the sea
It is forced up by mountains (high relief) and cools at higher altitude
As it cools, water vapor condenses into tiny water droplets forming CLOUDS.
Water droplets continue to grow in size & weight, they will no longer be suspended and will fall as rain (or possibly snow!)
Cool air holds less moisture
Most rain falls on the windward side of the relief
Leeward side is often in a dry rain shadow because the moisture has all been lost

17. Definitions Windward The side of the mountain receiving the wind
(consequently more precipitation as well)
Leeward
The side of the mountain sheltered from the wind
(consequently receives less precipitation)
Rain Shadow
The area located on the leeward side of a mountain that receives low amounts of precipitation.
Mainly due to the air that descends on the leeward side has “dumped” on the windward side.

18. Describe Frontal rainfall p. 66
Weather Front-2 fronts meet
Hence the name frontal rain
FRONT
Warm, moist air
Warm Moisture laden air meets cold air
Warm air is less dense & is forced up over the cooler, more dense air
As it cools, water vapor condenses into tiny water droplets forming CLOUDS.
Water droplets continue to grow in size & weight, they will no longer be suspended and will fall as rain (or possibly snow!)
Cool air holds less moisture

19. Describe Convectional rainfall p. 67
Often associated with thunder storms.
Air heated from the earth
Usually occurs in hot areas like tropics or continental summer
Sun heats the earth causing large amounts of water to evaporate
Hot air rises forming convection currents (hence the name)
As it cools, water vapor condenses into tiny water droplets forming CLOUDS.
Water droplets continue to grow in size & weight, they will no longer be suspended and will fall as rain (or possibly snow!)
Cool air holds less moisture

20. Analyze the relationship between wind systems and temperature.
How do the prevailing winds affect temperature in:
Columbia
Baffin Island
Newfoundland

21. B -Baffin Island
C - Newfoundland
A - Columbia

22. Analyze the relationship between wind systems and precipitation
How do the prevailing winds affect precipitation in:
England
Midwestern U.S.
British Columbia
Northern Africa
Central Australia
Question #26 p. 67 = great active learning lab

23. A - England
C - British Columbia
B - Midwestern U.S.
D - Northern Africa
E - Central Australia