4 What is wind A windsock that is filled with strong wind hangs horizontally Wind is another name for moving air Air is a mixture of gases that together make up the atmosphere that surrounds the Earth Our atmosphere contains nitrogen oxygen argon and small amounts of carbon dioxide as well as other gases Air moves all around our planet It can be gentle or forceful Gentle winds can fly a paper kite strong winds can tear down trees What makes wind blOw The Sun heats whatever it touches and when it heats up air the air becomes warmer and lighter Warm air is lighter than cool air so it rises Cool air moves in to replace the warm air This movement of warm air rising and cool air replacing it is what creates breezes winds and even hurricanes WindsOcks Even the most technologically-advanced airports still use windsocks to show the strength and direction of the wind The wind fills the sock and makes it point away from the direction the wind is coming from When the wind is strong the sock will point almost horizontally but it will hang down when there is little or no wind
Weathervanes A weather vane is mounted on a roof or tower and swings round as the wind blows always pointing in the direction itZs blowing It often has a cockerel on the top which is why it is sometimes called a weather-cock Below the cockerel are the four points of the compass They are fixed in place and show where the wind is coming from and blowing to Weather ballOOns Weather balloons are instruments for collecting and measuring information about the air high above the ground They are filled with hydrogen or helium which are both gases that are much lighter than air They can rise about 25 miles above the ground They carry a radio probe that records information on atmospheric pressure temperature humidity and wind speed 5 A traditional weather-cock shows wind direction KEY WORDS gas atmosphere windsock weather vane compass weather balloon wind speed Weather balloons are released twice daily from 800 locations around the globe
6 Breeze to gale How fast the wind is blowing can be very important A gentle breeze can be pleasant on a sunny day A gale can blow you over if you’re not careful And a hurricane is dangerous and can tear down houses as well as trees WIND SPEED Depending on their strength winds can be known as a breeze a gale a storm or a hurricane The speed is often measured in knots A breeze travels at 17-21 knots and a hurricane at over 70 knots A knot is the number of nautical miles travelled in one hour The Beaufort scale Wind is measured on the Beaufort scale from 0-12 At zero there is no breeze so smoke from a fire rises vertically into the sky A reading of Force 6 is a strong breeze 9 is gale force and 12 is a hurricane 1 Light air 2 Light breeze 5 Fresh breeze 6 Strong breeze 9 Strong gale 10 Storm
Measuring wind An anemometer is an instrument used to measure wind It is a tall rod with small cups attached to it The wind spins the cups around and the speed of the spin gives a measurement of the force of the wind An anemometer 3 Gentle breeze 4 Moderate breeze 7 Near gale 8 Gale 7 KEY WORDS gale hurricane knot Beaufort scale anemometer 11 Violent storm 12 Hurricane The Beaufort Scale measures the force of the wind on a scale of 1 to 12
