Understanding Wind Patterns and Local Winds

Winds Chapter 2, Section 3 p. 52-60

What causes wind? What causes wind? Wind: The horizontal movement of air from an area of high pressure to an area of lower pressure.

What causes winds? What causes winds? All winds are caused by differences in air pressure HIGH LOW

What causes these What causes these differences in pressure? differences in pressure? Unequal heating of the atmosphere Remember convection currents? As air becomes less dense, its air pressure decreases.

Measuring Wind Measuring Wind Winds are described by their direction and speed

Measuring Wind Measuring Wind To measure wind direction: we use a wind vane

Measuring Wind Measuring Wind To measure wind speed: we use an anemometer

Wind Wind- - Chill Factor Chill Factor Wind Chill Factor: Increased cooling caused by the wind

Local Winds Local Winds Local winds: winds that blow over short distances

Local Winds Local Winds Local winds are caused by unequal heating of Earth s surface within a small area

Local Winds Local Winds Example: cool breezes blowing in from the water to the beach.

Sea Breeze Sea Breeze Sea Breeze:The flow of air from an ocean or lake to the land. Daytime!

Land Breeze Land Breeze Land Breeze: The flow of air from land to a body of water. Night time!

Land Breeze/ Sea Breeze Land Breeze/ Sea Breeze

Monsoons Monsoons Monsoons: Sea and land breezes over a large region that change directions with seasons

Global Winds Global Winds: Winds that blow steadily from specific directions over long distances

Temperatures Temperatures near the equator are much warmer than the temperatures near the poles.

Intermission Chapter 2, Section 3 p. 57-60

Global Convection Currents Temperature differences between the equator and the poles produce giant convection currents in the atmosphere.

Global Convection Currents This movement of air between the equator and the poles produces global winds.

The Coriolis Effect Coriolis Effect: The way Earth s rotation makes winds curve. Give students this analogy: Assume a plane takes off from some northern location in the U.S. (pick one from your area) and flies several hours due south (pick another location). When the plane arrives, the destination city has moved east due to the Earth s rotation. To really reach the destination due south, the plane actually has to fly a curved path to where the city will be when the plane lands. This is what happens with the air turning to the right.

In the Northern In the Northern Hemisphere Hemisphere Global winds turn toward the RIGHT In the Southern In the Southern Hemisphere Hemisphere Global winds turn toward the LEFT

Global Wind Belts The 3 major wind belts are the: 1. trade winds 2. prevailing westerlies 3. the polar easterlies

Global Wind Belts The 2 calm areas are the: 1. Doldrums 2. Horse Latitudes

Global Wind Belts

Doldrums A calm area where warm air rises Regions near the equator with little or no wind

Horse Latitudes A calm area of falling air Latitudes 30 north and south of the equator

Trade Winds Steady easterly winds which blow from the horse latitudes toward the equator.

Prevailing Westerlies Winds in the mid latitudes which blow from the west to the east. Play an important part in the weather of the United States

Polar Easterlies Cold air near the poles which sinks and flows back toward lower latitudes.

Global Wind Belts

Jet Streams Jet Streams: Bands of high-speed winds about 10 kilometers above Earth s surface