Local and Global Wind Systems S6E4c. Develop a model demonstrating the interaction between unequal heating and the rotation of the Earth that causes local and global wind systems.

What is wind? Wind is moving air and is caused by differences in air pressure within our atmosphere. High pressure always moves towards low pressure The greater the difference in wind, the faster the air flows Wind is described using direction and speed Local winds are named for where they originate (begin)

Types of Wind Local Winds Global Winds Smaller wind systems that affect local weather Sea Breezes and Land Breezes Mountain and Valley Breezes Larger wind systems that determine major weather patterns for the entire planet

Let’s Review Air Pressure Air pressure is the measure of the force with which air molecules push on a surface Air pressure is greatest at the surface of Earth because there are more air molecules pushing down from above

As you increase in altitude, air pressure decreases. There are fewer air molecules above you to push down, so the force will be less This Photo by Unknown Author is licensed under CC BY-SA

Air Pressure is dependent on density More dense air will have higher air pressure – there are more molecules in a given space to push down on you Less dense air will have lower air pressure – there are fewer air molecules to push down on you

Temperature and Air Pressure Warm air is less dense than cold air, so warm air has lower air pressure and cold air has higher air pressure. Molecules in cold air are moving slowly and are close together = high air pressure Molecules in warm air are moving fast and are spread further apart = low air pressure

Partner Share Land heats and cools faster than water. How does this affect wind?

Sea Breeze High Pressure 65°F 85°F Low Pressure Look at the temperatures of the land and the sea in this diagram. Where is the low and high pressure? Which direction would the wind blow? Explain High Pressure Sea Breeze The wind will blow from the sea to the land because it is a cooler temperature which means higher pressure and winds flow from high pressure to low pressure. 65°F 85°F Low Pressure

Land Breeze 65°F 55°F Low Pressure High Pressure At night when the earth’s surface is no longer being heated by the sun, the land cools much more rapidly than ocean water. What happens to the wind? Land Breeze The wind changes direction, now originating from the land since the temperature is lower than that of water. Pressure still moves from high to low pressure. 65°F 55°F Low Pressure High Pressure http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm?chapter_no=visualization

Land Breeze Sea Breeze

Mountain and Valley Breezes Mountain Breeze (Night) Valley Breeze (Day) The cool air moves down the slopes into the valley. During the day, the sun warms the air on the slopes creating a valley breeze. The cool air pushes the warm air up the slopes

Global Winds Created by unequal heating of Earth’s surface Warm Air = less dense  warm air rises at the equator Cool Air = more dense  cool air sinks at the poles The movement of air between the poles produces patterns of circulation called global winds The circular motion of the winds is created by the Coriolis Effect

Use this diagram to fill in your notes

Local and Global Winds http://studyjams. scholastic Local and Global Winds http://studyjams.scholastic.com/studyjams/jams/science/weather- and-climate/air-pressure-and-wind.htm