Global and Local Winds

Air Movement Wind is the horizontal movement of air from high pressure to low pressure. It is caused by differences in air pressure The greater the difference, the faster the wind moves

Air Pressure Differences in air pressure are caused by the uneven heating of Earth Cool, denser air with a higher pressure flows underneath the warm, less dense air. This forces the warm air to rise.

Wind Vane- measures wind direction Wind Vane- measures wind direction.- tells you where the wind is coming from. Ex: a north wind comes FROM the north. Barometer- measures air pressure Anemometer- measures wind speed. Wind chill factor- the increased cooling a wind causes.

Wind Chill Why does a cool breeze feel refreshing in the summer, but cold in the winter? Wind blowing over your skin removes body heat. The stronger the wind, the colder you feel.

Local Winds Generally move short distances and can blow in any direction Caused by geographic features that produce temperature differences Caused by the unequal heating of Earth’s surface within a small area.

It takes more energy to warm up and cool down a body of water than it does to warm up land. Wherever the cool air is located, that is the type of breeze. Ex: sea breeze- cool air is over the sea.

Sea Breezes High pressure is created over the ocean (cooler air) during the day and low pressure (warmer air) over land due to uneven heating Air moves from the ocean to the land creating a sea breeze

A. Sea Breeze Happens during the day. Land warms up faster than the water. Air over the land becomes warmer than air over the water. The warm air expands and rises, creating a low-pressure area. Cool air blows inland from over the water and moves underneath the warm air, causing a sea breeze. Sea Breezes blow FROM THE SEA.

Sea Breeze

Land Breezes Low pressure occurs over the ocean during the night and high pressure over land due to the uneven heating of earth This causes wind to move from the land to the ocean creating a land breeze

B. Land Breeze 1.Happens at night. Land cools more quickly than water. Air over the land becomes cooler than air over the water. Warmer air over the water expands and rises. Cooler air from land moves beneath it. Land Breezes blow FROM THE LAND.

Land Breeze

Sea and Land Breeze animation http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm

Question 1 What causes winds?

Answer Winds are caused by the uneven heating of Earth’s surface, which causes pressure differences

Teach Time Teach your neighbor about land and sea breezes.

Pressure Belts Uneven heating produces pressure belts which occur every 30° latitude

As warm air rises at the equator and moves toward the poles, it cools Pressure Belts As warm air rises at the equator and moves toward the poles, it cools As it cools, some of the air sinks around 30° north and south of the equator

At the poles, cold air sinks and moves towards the equator Pressure Belts At the poles, cold air sinks and moves towards the equator Around 60° north and south, the air begins to heat up and rise

A. Coriolis Effect As the winds blow, Earth rotates from West to East underneath them, making it seem as if winds are curving. Global winds in N. Hemisphere turn toward right. S. Hemisphere, winds curve toward left.

These are polar easterlies, westerlies, and trade winds Global Winds The combination of pressure belts and the Coriolis Effect cause global winds These are polar easterlies, westerlies, and trade winds

Global Winds Winds that blow steadily from specific directions over long distances. Created by the unequal heating of Earth’s surface. Near the equator, sun’s rays strike earth directly. Near the poles, sun’s rays do not strike Earths’ surface directly. The sun’s energy is spread out over a larger area, so it heats the surface less. Therefore, temps. Near the poles are lower than near the equator.

5. Temp. differences btwn equator and poles create giant convection currents, movements of air between the equator and poles. 6. Warm air rises at the equator and cold air sinks at the poles. 7. Air pressure tends to be lower near the equator and greater near the poles. Winds at the surface blow from poles toward equator. High in the atmosphere, air flows away from the equator toward the poles. They curve because of Earth’s rotation.

Wind belts that extend from the poles to 60° latitude Polar Easterlies Wind belts that extend from the poles to 60° latitude Formed from cold sinking air moving from the poles creating cold temperatures

E. Polar Easterlies Cold air near poles sinks and flow back toward lower latitudes (away from the poles). Mixing of warm and cold air along the polar front has major effect on weather in US.

Wind belts found between 30° and 60° latitude Westerlies Wind belts found between 30° and 60° latitude Flow towards the poles from west to east carrying moist air over the Unites States

D. Prevailing Westerlies mid-latitudes, btwn 30 and 60 North and South, winds blow toward poles are turned toward the east by Coriolis effect. Winds blow west to east. PLAY IMPORTANT ROLE IN WEATHER IN USA.

Winds that blow from 30° almost to the equator Trade Winds Winds that blow from 30° almost to the equator Called the trade winds because of their use by early sailors

C. Trade Winds Cold air over horse latitudes causes high pressure when it sinks. High pressure causes surface winds to blow toward equator and away from it. Winds that blow toward equator are turned west by Coriolis effect. Winds are high and they help ships get across the ocean. In the Northern Hemisphere, they move from the NE. In the Southern Hemisphere, they move from the SE.

Doldrums Located along the equator where no winds blow because the warm rising air creates and area of low pressure

A. Doldrums Near equator, sun heats surface strongly. Warm air rises, creating low pressure. Cool air moves into area, but is warmed rapidly and rises before it moves very far. Little or no wind there (very calm)

B. Horse Latitudes Warm air rises at equator and flows both north and south. At 30 degrees north and south, air stops moving toward poles and sinks. Calm air is here.

Most deserts on the Earth are located here because of the dry air Horse Latitudes Occur at about 30° north and south of the equator where the winds are very weak Most deserts on the Earth are located here because of the dry air

Separates warm air from cold air Jet Stream The jet streams are narrow belts of high speed winds that blow in the upper troposphere and lower stratosphere Separates warm air from cold air

F. Jet Streams Bands of high-speed winds about 10km above Earth’s surface. They are hundreds of km wide but only a few km deep. Jet streams blow from west to east at speeds of 200-400km/hr.

What are the three types of global winds? Question 2 What are the three types of global winds?

Answer Polar Easterlies Westerlies Trade Winds

What is the difference between a land breeze and a sea breeze? Question 3 What is the difference between a land breeze and a sea breeze?

Answer Sea breezes occur during the day when the land is warmer than water and a land breeze occurs at night when the water is warmer than land

Bill Nye http://www.youtube.com/watch?v=JfeaCU2y6t4 – Wind http://www.youtube.com/watch?v=dz4fgG9ZCIc - Atmosphere

Mr. Parr Winds Blow http://www.youtube.com/watch?v=g4O9z_R5ZSc