Wind; The Movement of Air

Chapter 4, Outcome 2.3

The Rules

• In order to understand wind there are 4 rules

• 1. We name pressure systems as alternating with a low over the equator.

• 2. Air moves from areas of high pressure to low

• 3. Air is deflected to the right in the north and to the left in the south

• 4. We name winds based on where they come from

Pressure Systems

• When air is heated it tends to rise causing low pressure. Cooling air drops causing high pressure.

• This causes a sort of convection cell to be created

Air Movement

• Air that is moving horizontally is called wind.

• Wind always moves from areas of high pressure to low pressure

• This happens as air from the high rushes in to replace air that is rising from the earths surface

Coriolis Effect

• This law says that in the northern hemisphere, free moving objects will appear to deflect to the right while in the southern hemisphere its to the left.

» This occurs because the earth is

rotating

Coriolis Effect…..

Coriolis Effect…..

• Remember that the wind turns to the left or right relative to its direction. The diagram to the right is correct. Does it make sense?

Wind Names

• Finally we name the winds from where they come from

Local Winds…..Land and Sea

• A land breeze works the same as a global wind

• Here air over the water is warmer and land is cool• Air over the water is rising and air from the land moves

toward the water (high to low)• Its called a land breeze because the air comes from….

Local Winds…..Land and Sea

• A sea breeze occurs when the land is warm and the sea is cooler (daytime)

• Air over the land is rising and air from the water moves toward the land (high to low)

• Its called a sea breeze because the air comes from….

Monsoons

• Parts of the world have wet and dry seasons because of seasonal rains.

• These are called monsoons and are caused by the same things as winds.

• Air moves from highs to lows and if it is coming from the water we get wet seasons.

• Later in the year the pressure changes place and we get a dry season….. Take a look!!!!

Monsoons

• In summer the land heats up and so the air rises causing a low. The water heats slower so it is a high. The wind moves from the water making it the wet season

• In winter the water heats up and so the air rises causing a low. The land cools quickly so it is a high. The wind moves from the land making it the dry season

Life in India

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Now Lets Draw……