1. Explain the causes of winds on the Earth.
2. Explain the differences between land breezes and sea breezes, and their causes.
3. Describe the Coriolis Effect
4. Explain how the Coriolis Effect and the unequal heating of the Earth affect the global wind systems.
5. Describe the location of the polar easterlies.
6. Describe the location of the prevailaing westerlies.
7. Explain the trade winds.
8. Describe the doldrums.
9. Explain air currents and jet streams.
10. Explain how air currents move geographically from time to time during a year.
11. Describe the impacts of air currents on the surface of the Earth.

Wind

Air flows form areas of higher pressure to areas of lower pressure.

Differences in air pressure are caused by uneven heating of the Earth's surface. Therefore, the sun (solar energy) is the ultimate cause of wind.

Land and Sea Breezes

This causes temperature differences between the land and the sea, which leads to a thermal circulation (or wind based on temperature differences).

During the day, the land gets hotter faster, and the hot air rises, creating an area of lower pressure. Wind blows from the sea to the land. This is a sea breeze.

At night, the land cools off faster than the sea. Cooler air descends creating an area of higher pressure. Wind blows from the land to the sea. This is a land breeze.

Much of the solar energy that the earth receives causes intense heating in the equatorial regions.  This intense heat produces powerful convection in these areas.

As the warm, moist air rises, it creates a zone of low pressure, clouds, and precipitation along the equator.  As that warm air rises, it eventually reaches the troposphere and can rise no higher.  It spreads outwards towards the poles.

As it spreads, it cools and sinks back down to the surface at about 30 degrees north and south of the equator.  This sinking air produces areas of higher pressure with drier conditions.

Many of the world's deserts are located in these high pressure areas, around 30^o north and south of the equator.
Examples?
Sahara Desert
Great Victoria Desert, Australia
Kalahari Desert
Sonoran Desert

Some of this air, as it sinks, moves back towards the equator. This air flowing back towards the equator produces what is know as the trade winds.

The trade winds obtained their name from the sailing ships used in foreign trade, which were called traders. These winds propelled the ships from Europe to the New World.

The area near the equator where these winds die out is referred to as the doldrums.

These areas where air rises at the equator, sink at 30 degrees north and south latitude, and then flow back to the equator are known as Hadley cells. Although most of the air that sinks at 30 degrees north and south latitude returns to the equator, some of it continues to move poleward.

At approximately 60 degrees north and south, this air meets cold polar air. The areas where these air masses meet form polar fronts. The air moving in from the lower latitudes is generally warmer and will rise. It then moves back towards the equator, sinking at about 30 degrees north and south. This sinking air contributes to the high pressure systems located there.

The circulation cells that form between 30 degrees and 60 degrees north and south are called Ferrel cells.

Some of the air that rises at the polar fronts continues to move poleward, sinking at the poles and then moving back towards 60 degrees north and south.
These Hadley cells are weaker than the tropical ones.

As the air that sinks at these locations flows back along the surface of the earth, it does not flow in a straight north-south path. This flow of air is affected by the Coriolis Effect.

The Coriolis Effect

• Turn to the right of its direction of motion in the Northern Hemisphere and
• Turn to the left of its direction of motion in the Southern Hemisphere.