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

Transcription

1 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 Unequal heating! What causes wind? 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)

4

5 Know that air blows from areas of high pressure to areas of low pressure. The statement is fact. Real examples: 1. Air inside a balloon 2. Exhaling 3. 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 Low Pressure Relative Low pressure over sea Cold land air moves to lower 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 Wind: 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

13 Describe how the coriolis force affects wind direction. Coriolis force = 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.63 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 Windward Leeward Chinook 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 Warm, moist air FRONT Hence the name frontal rain 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!)

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: 1. England 2. Midwestern U.S. 3. British Columbia 4. Northern Africa 5. Central Australia Question #26 p. 67 = great active learning lab

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