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
8 MOving gases Wind is moving air and air is a mixture of gases in a thick layer stretching from ground level up about 310 miles into space but most of the air is in the 10 5 miles-thick layer nearest Earth’s surface called the troposphere Oxygen Oxygen takes up 21 of the space in the troposphere Nitrogen takes up 78 In the oceans nitrogen forms 88 of the oceanZs mass It is the third most abundant chemical element in the universe after hydrogen and helium Oxygen and carbon dioxide are the gases that affect Earth most thermosphere mesosphere stratosphere troposphere Gases in the air 99 of EarthZs atmosphere is made up of about 4 parts of nitrogen to 1 part of oxygen The other 1 is mostly the gases argon and carbon dioxide with tiny traces of other gases The reason there is so much nitrogen in our air is because it is a heavy gas It doesnZt drift up and away from the pull of EarthZs gravity like lighter gases such as helium or hydrogen
CarbOn diOxide When we breathe we use the oxygen in the air to release energy in our body We breathe out carbon dioxide and water vapor Much of the carbon dioxide is absorbed by plants that combine it with light and water to produce energy The plants release oxygen back into the atmosphere In addition fossil fuels such as coal gas and oil release carbon dioxide into the atmosphere when they are burned Since we are using more and more fossil fuels so more and more carbon dioxide is being released into the atmosphere Burning fossil fuels releases carbon dioxide into the air 9 A demonstration team the Red Arrows leaves colored air trails of carbon dioxide as it speeds past
