1. Notes on “Air Movement”
Pictured is a wind farm off the coast of Massachusetts, U.S. Currently, wind energy accounts for less than 1% of the U.S. energy supply.  However, wind energy could supply up to 20% of the nation's electricity according to the National Renewable Energy Laboratory.
Earth/Space

2. Discuss the Coriolis effect
S.W.B.A.T.
Explain why Earth receives different amounts of solar energy at different latitudes
Discuss the Coriolis effect
Identify and locate the doldrums, trade winds, prevailing westerlies, polar easterlies and jet streams
“Students Will Be Able To…” - another way to state the lesson objectives.

3. Earth is unevenly heated by the Sun due to its curved shape
Wind Formation
Earth is unevenly heated by the Sun due to its curved shape
Warmer air expands and becomes less dense than colder air
Air pressure is lower where air is heated and expands
Areas of permanent low-pressure exist at the equator; permanent high-pressure areas are at the poles. Low-pressure has rainy/cloudy weather associated with it while high-pressure systems have very little clouds and little to no precipitation.

4. Movements of air create convection currents
Wind Formation
Wind – the movement of air from areas of higher pressure to areas of lower pressure
Heated air at the equator is less dense and is replaced by denser colder air from the poles
Movements of air create convection currents
Uneven heating of Earth’s surface also causes convection cells to form. The process of convection is the main means of heat transfer within a fluid that is exposed to a heat source (previous lesson).

5. Video (1:54) “Bill Nye: Wind”
In meteorology, convectional currents are a form of small to high speed winds and one of the many forms of convection on Earth. These winds can be anything from a few knots to in the knot range. Convection currents are caused by a difference in pressure and heat in the tropical and Antarctic/Arctic areas on the earth.
Wind Direction

6. This is called the Coriolis effect
Wind Formation
Earth’s rotation causes air and water to turn clockwise (or to the right) north of the equator and counter-clockwise south of the equator
This is called the Coriolis effect
Named after the scientist who was laid the groundwork for rotating forces and water – French mathematician, engineer & scientist Gustave Coriolis (1820’s).

7. Wind Formation
Solar heating differences and the Coriolis effect create different wind patterns on Earth’s surface
These wind patterns influence the weather and determine when and where ships and planes can efficiently travel
An excellent but 6-minute long video on youtube explains the Coriolis effect as well as the conservation of angular momentum – the video may be a little
advanced for 6-9th grades.

8. Doldrums – wind band located along the equator
Global Winds
Doldrums – wind band located along the equator
Heated air expands, rises and forms a low-pressure zone
Very little to no wind; cloudy and rainy afternoons
Sailors referred to the area as the “doldrums” to signify the negative effects of having no wind to fill their sails and constant rain in the afternoons when water vapor rose and condensed. Not to be confused with the “horse latitudes” which are degrees north and south latitudes and are areas of high-pressure with little to no wind or rain. Due to the sometimes weeks-long lull in travel that sailing ships had to endure if caught in the horse latitudes – the Spanish would jettison their horses overboard because of the lack of fresh water.

9. Trade winds – wind bands just north and south of the doldrums
Global Winds
Trade winds – wind bands just north and south of the doldrums
Air cools and sinks back towards the equator
The Coriolis effect deflects the surface winds to the west where ships sailed to trade
Sailing ships from Europe used the trade winds because of their reliability in use of travel to the New World – and to trade in particular.

10. Global Trade Winds
All of the belts move north during the northern summer and south during the northern winter. Because global heating and cooling lags behind the position of the sun they reach their northernmost latitude at or after the end of the northern summer.

11. Global Winds
Westerlies – between 30 and 60 degrees north and south of the equator, winds blow in the opposite direction of the trade winds
Prevailing westerlies are responsible for much of the movement of weather systems in the United States
The “prevailing westerlies” are so named because the winds “prevail” or blow from the west to east – opposite of the trade winds that blow east to west. When Columbus sailed he knew about the trade winds and the westerlies – which few sailors realized at the time. Columbus’ men were not told of the westerlies and feared they would not make it back to Spain because of the dominance of the east-to-west flow of the trade winds.

12. Prevailing Westerlies
Prevailing Westerlies are the winds in the middle latitudes between 35 and 65 degrees latitude. They tend to blow from the high pressure area in the horse latitudes towards the poles and aredeflected by the Coriolis effect.

13. Polar Easterlies – found near the poles
Global Winds
Polar Easterlies – found near the poles
Winds again shift back or prevail from east to west due to Earth’s rotation
The Polar easterlies are located at the poles next to the westerlies. They are formed as cold air at the poles sinks and begin to move towards the equators. However, as they meet warmer air form the westerlies, they create a polar front located at 60 degrees north and south which is an area of low pressure that often results in storms. Polar easterlies affect the weather in northern Canada and Alaska.

14. (Trade Winds)
A review of global winds covered so far. Trade Winds are also known as tropical easterlies.

15. Global Winds
Jet streams – narrow belts of strong winds that blow near the top of the troposphere
Polar jet streams form a boundary between cold, dry polar air and moist, warm tropical air to the south
Jet streams were first discovered by WWII bomber planes trying to fly above anti-aircraft fire. The planes’ speed – relative to the ground – increased by over 200 km/hr when reaching a certain altitude. An area of very fast winds in the upper troposphere were soon deduced.

16. Jet streams can help move or direct storm systems from west to east
Global Winds
Jet streams can help move or direct storm systems from west to east
Jet pilots will take advantage of the jet stream when flying west to east to save time and fuel
Polar jet streams are much stronger in the winter due to a larger temperature difference in the north and south. Sub-tropical jet streams are stronger in the summer due to the same effect. Meteorologists closely follow the jet stream path – as it can meander or move like a river of air in the sky – to predict storm movement and formation.

17. Local Winds
Global wind systems direct the major weather patterns for the whole planet
Local winds affect areas on a much smaller scale depending on geographic location
Local winds are winds that blow over short distances caused by unequal heating of the Earth’s surface in a small area.

18. Sea Breezes – land is heated quicker during the day
Local Winds
Sea Breezes – land is heated quicker during the day
This causes air to rise over the land & moist, cool air from the sea to rush in
Area of localized low-pressure occurs overland during the day. Facing the beach you would feel the wind blowing in from the water.

19. Land Breezes – land cools much quicker at night than water
Local Winds
Land Breezes – land cools much quicker at night than water
Warmer air over the water rises & cooler air over the land rushes in
Area of localized low-pressure develops over the water at night. Facing the beach you would feel the wind at your back. Ask students if they have experienced these local winds while at the beach during the day or night.

20. Sea Breeze vs. Land Breeze
Video (1:38) “5-Minute Science: Land and Sea Breezes”
Each local wind creates a convection cell or current. Areas of localized high pressure will have sinking air – low pressure = rising air.

21. With arrows indicate from which direction the wind blows
Class Activity
On a world map draw and label the locations of the doldrums, trade winds, westerlies and polar easterlies
With arrows indicate from which direction the wind blows
Students may use their textbook or an online resource if available. Students should start with using a ruler to find and draw/label the equator (doldrums).

22. This slide is available for printing for use in the class activity
This slide is available for printing for use in the class activity. A hyperlink is also included (click on the picture) to take you to the original website.