World Geo 32022.3 WINDS

Understand the cause of winds and how they affect climate

Chapter 4 Pages 59-67

2.3.1 Air moves from areas of high pressure to areas of low pressure.

Think of:1. Air inside a balloon2. Air exhaled from a person’s lungs3. Air powered pellet gun

The movement of air from high and low pressures in the earth’s atmosphere are responsible for wind!

P. 59-61

2.3.1 What is Wind?

Wind: * It is the flow or movement of air.

* It results from air masses of different temperatures lying next to each other

* The resulting pressure variation causes “wind” to blow from high pressure area to low pressure area.

2.3.1 Define the term Prevailing Wind. p.61-63

More on these later!

Prevailing Winds:•They are regular, predictable, normal winds in the same direction•They are caused by global convection cells

2.3.2 Describe conditions that result in Land and Sea Breezes

Sea Breezes:

1. During the day the land heats much faster than the water, consequently the air over the land heats and rises.

2. The rising air over the land leaves a relatively low pressure. The air pressure over the water is relatively high, therefore wind blows from high pressure (water) to low pressure (land)

3. Hence the name 'sea breeze'—the wind is blowing off the sea.

Land Breezes:

1.The sea air is warmer than land air. Because this air is warmer, it rises and leaves a relatively low pressure over the sea.

2.The land air then blows to the low pressure over the sea.

Remember—winds are named for where they come from.

For example, easterly winds come out of the east; southerly winds come out of the south; sea breezes come from the sea.

2.3.2 Describe Conditions that result in Land and Sea Breezes

Land BreezeSea Breeze

•Land air is warmer than sea air

•Air rises over land, leaving a relative low pressure

•Sea air moves to lower pressure

•Sea air warmer than land air

•Air rises over sea, leaving a relative low pressure

•Land air moves to lower pressure

2.3.3 Describe how the Coriolis Effect affects Wind Direction.Coriolis Effect: In northern hemisphere, objects in motion tend to

deflect to the right In southern hemisphere, objects in motion tend to

deflect to the south

Impact on winds: In the northern hemisphere, winds tend to

curve to the right In the southern hemisphere , winds deflect

to the left.

Coriolis Effect

2.3.4 Wind Systems relate to Pressure Belts Global convection cells are cycles of air

movement over the earth They are created because of the differential

heating of the earth's surface As the equatorial regions heat the air, it rises

creating a low pressure at the equator. The rising air cools, falls to earth at 30º  North/South, leaving high pressures.

The other lows and highs can be predicted every 30º of latitude north and south!

Alternating high and low pressures result from the convection cells.

A low pressure belt is created at the equator and at 60º N and 60º S, while high pressure belts are created at 30º N and 30ºS, and at the poles.

Prevailing winds form global patterns because of these global pressure belts. They follow the laws of physics and blow from the high pressure belts to the low pressure belts.

2.3.4 Make inferences about how winds are related to major pressure belts. p.63 Air rises from the equator Settles at the poles Result is 6 convection cells 3 above and 3 below the equator.

Low pressures result where hot air rises.

High pressures result where air cools and settles

2.3.5 Explain how wind systems and temperature are related.

Prevailing winds from the south bring warm air toward the north, such as the Westerly Winds. Whereas the North Polar Easterlies bring cold air from the north toward the south.

Prevailing Winds

2.3.5 Explain how wind systems and temperature are related.

How do the prevailing winds affect temperature in:

1. Argentina

2. Columbia

3. Baffin Island

4. Newfoundland

Remember!

The affect on temperature varies with seasons as well! Wind off the land in summer results in heat, whereas, wind off the land in the winter results in cold temperatures.

Land heats up faster than water and therefore the wind blowing over it will pick up the heat. Conversely, land also cools down faster than water and winds blowing over the frozen cold interior will lose its heat.

2.3.6 Define windward, leeward and rain shadow

Windward is on the side facing the wind. Wind carries precipitation

Leeward is on the side sheltered away from the wind. Wind is usually drier

Rain shadow is a dry area on the leeward side of a mountain

2.3.7 Type of rainfall is located to nature of location Types of rainfall:

1. Relief/Orographic Rainfall

– moist air blows off the sea;

– it is forced up by mountains (high relief);

– air cools at higher altitudes;

– cool air holds less moisture;

– clouds condense and rain falls;

– most rain falls on the windward side of the relief;

– the leeward side is often in a dry rain shadow because the moisture has all been lost.

Types of rainfall:

2. Frontal Rainfall – Warm Moisture laden air meets cold air; – warm air is less dense & is forced up over the

cooler, more dense air; – warm moisture laden air cools at higher

altitude; – cool air holds less moisture; – clouds condense and rain falls.

Types of rainfall:3. Convectional Rainfall

– 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;

– warm moisture-laden air cools at higher altitude;

– cool air holds less moisture;

– consequently clouds condense and rain falls.

2.3.8 Explain the relationship between wind systems and precipitation

Prevailing winds blowing off the ocean and onto the land results in high precipitation. Especially if the wind is blowing off a warm ocean, like the Indian Ocean or the south Pacific.

If wind is blowing off the land, then there is very little moisture in it, resulting in low precipitation.

Knowing the direction of winds over mountains is also important in predicting precipitation.

The windward side of a mountain is going to receive the greatest rainfall, while the leeward side will find itself in a rain shadow.

2.3.8 Explain the relationship between wind systems and precipitation

How do the prevailing winds affect precipitation in:

1. England2. Midwestern U.S.3. British Columbia4. Northern Africa5. Central Australia Question #26 p. 67: