What causes the wind to blow? How is wind created? The uneven heating of the Earth's surface by the sun creates wind. What causes the wind to blow? As the sun warms the Earth's surface, the atmosphere warms too. Some parts of the Earth receive direct rays from the sun all year and are always warm. Other places receive indirect rays, so the climate is colder. Warm air, which weighs less than cold air, rises. Then cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow.

Global Winds vs. Local Winds · movement of air across large distances. · they flow high up in Earth's atmosphere. · they move in predictable patterns and do not change much. · move across smaller distances. · move closer to the Earth's surface. · respond to changes in air pressure. · they are less predictable, because they change with the weather.

Heating & Cooling Causes Global Winds · The sun heats the Earth more at the Equator and less at the poles. · Air moves across the Earth to distribute this heat more evenly. · This creates global winds that flow between the Equator and the poles. · These winds change direction at different latitudes due to the rotation of the Earth.

Global Wind #1: Polar Easterlies Look at the words 'Polar' and 'Easterlies', where do you think these winds are coming from? · Cold winds that begin in the east and blow toward the west. · These winds begin and blow away from the poles (North & South Poles) · Why do these winds blow away from the poles? (hint: Think about what cold air wants to do)

Global Wind #2: Prevailing Westerlies Look at the word Westerlies, where do you think these winds are coming from? · Move from west to east. · These winds affect our weather by:· Moving systems (High Pressure and Low Pressure) from west to east across the United States. · Moving fronts (Warm, Cold, Stationary, Occluded) from west to east.

Global Wind #3: Trade Winds · Wind moving towards the Equator · Blows from East to West. · Warm, steady breezes that blow almost continuously. · Called Trade Winds due to their ability to move trading ships across the ocean.

Jet Streams A jet stream is a band of fast-moving wind located 5 – 7 miles above earth’s surface that flows from west to east. Where a jet stream flows over North America, it greatly affects the weather. Jet streams affect the paths of storms and movement of high and low pressure systems.

Types of Jet Streams Jet streams do not follow regular paths around Earth. Instead, they dip, bend, and change position. When the polar jet stream dips south, it lets cold air from Canada flow down into the USA (this is the main one that affects our weather). When the subtropical jet stream bends north, it lets warm air flow in from the South.

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Think, Pair, Share What is the name of the global wind that moves weather systems across the USA? What is a jet stream? What jet stream affects the USA the most? How does the jet stream affect temperatures and movement of weather systems?

Local Breezes Water takes a long time to heat and cool. Land heats and cools rapidly. Differences in the rate of cooling and heating between land and water create differences in air pressure. Remember, air always wants to go from high pressure to low pressure.

Sea Breezes During the day as warm air over the land rises (low pressure), cool air from over the ocean rushes in to takes its place (high pressure); this is called a sea breeze. Remember, air always wants to go from high pressure to low pressure.

Land Breezes During the night, the air temperatures switch; the warm air is now above the ocean since it takes longer for water to cool down, and the cool air is above the land since the land cools quicker. The warm air over the ocean rises (low pressure) and the cool air from the land rushes in to take its place (high pressure); this is called a land breeze. Remember, air wants to go from high pressure to low pressure.

Monsoons A monsoon is a sea breeze that occurs on a larger scale and for a longer time. A monsoon usually forms during the summer when the sun heats a large area of land. This warm air rises and cool air from the ocean rushes in to take its place. As the moist air from the ocean moves over the land, it produces heavy rain, often times for months. https://www.youtube.com/watch?v=uFilBJsu224

Hurricanes https://www.youtube.com/watch?v=4f45jA5UxB0

The Gulf Stream The Gulf Stream is a powerful Atlantic Ocean current that circulates warm water up the East Coast of the USA. The Gulf Stream impacts local weather by helping to keep temperatures along coastlines (like North Carolina’s) mild as it brings warm moist air to those areas. Current: the movement of the surface layer of water in response to the force of winds above it. Video Link: https://www.youtube.com/watch?v=rR5TFWNLtOc

El Nino *El Nino is a weather phenomenon where there is an unusual warming of the surface water in the eastern Pacific Ocean near the Equator. *This occurs sometime in December, every 3-5 years, lasting 9-12 months. *SST = Sea Surface Temperatures.

Effects of El Nino *The jet stream is pushed south during this time and this affects the track of storms, which in turn affects weather conditions. *For the east coast of the USA, during the winter, this means cooler temperatures and increased precipitation. *The west coast of the USA is also very wet. *It also means a less active Atlantic hurricane season. Video Link: http://education.nationalgeographic.com/education/activity/the-ocean-and-weather-el-nino-and-la-nina/?ar_a=1

La Nina *La Nina is a weather phenomenon where there is unusual cooling of the surface water in the eastern Pacific Ocean near the Equator. *This occurs sometimes in December, every 3-5 years, lasting for 9-12 months.

Effects of La Nina *The jet stream is pushed north during this time and this affects the track of storms, which in turns affects weather conditions. *For the east coast of the USA, during the winter, this means warmer temperatures and less precipitation. *It also means a more active Atlantic hurricane season.

Summary *We are currently expected to experience an El Nino pattern beginning this month.* Review: *What is the difference between El Nino and La Nina? *What are east coast winters like during each pattern? *During which pattern is the Atlantic hurricane season more severe?