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You can't see it, but you can see what it does. It ruffles your hair, tips over garbage cans and screeches through bare branches like a ghost in a bad mood. It flutters, blusters and howls all around us day in and day out. What makes the wind? What's floating around in it?
This will be a continuing series explaining air, pollutants and it's effects. Check out our web page monthly to follow our adventure.
Long ago the Japanese thought that a god named Fu Jin had a huge bag of wind. If he opened it just a little bit, the winds would be light; if he opened it a lot...WHOOSH! Other peoples thought the winds were kept in a cave or created by a god who squeezed his bellows in the sky. Today we know better.
Wind is created when air flows from an area of high pressure to an area of lower pressure. The sun heats up some parts of the earth more than others. The air above these "hot spots" is also warmed and rises. This rising air forms a low-pressure area. Air flows from higher-pressure areas to these low-pressure areas. Unless it gets bumped off course.
What's big enough to change the direction of the wind? The earth's spinning, for one thing. It forces the winds to turn right in the Northern hemisphere and left in the Southern hemisphere. Mountains, buildings and forests can alter the direction of the wind too, just as rocks in a stream change the water's flow.
If you live near the sea or a large lake, you've probably felt a breeze coming from the direction of the water during the day. This breeze starts up because the air above the land is heated more than the air above the water. The heated air above the land has lower pressure than the cooler air over the water. This cooler sea air from higher-pressure areas flows towards the lower-pressure areas over land. At night, the process reverses. The breeze flows from the land towards the water.
You don't need fancy instruments to know how fast the wind is moving. You just need to know the Beaufort scale. It's a wind-rating system named after its inventor, Sir Francis Beaufort, a British admiral. It describes how the wind behaves at various speeds. A calm day rates a 0, while a hurricane rates 12.
On April 12, 1934, the winds at the peak of Mount Washington in New Hampshire blasted right off the top of the Beaufort scale. They set a record reaching 231 mph.
|0||0 mph||Calm, smoke rises vertically|
|1||1-3 mph||Light air, not enough to move a wind vane, but shows in smoke drift|
|2||4-7 mph||Light breeze, wind felt on face, leaves rustle, wind vanes moved|
|3||8-12 mph||Gentle breeze, leaves and small twigs in constant motion|
|4||13-18 mph||Moderate, raises dust and loose paper, moves small branches|
|5||19-24 mph||Fresh, small trees in leaf begin to sway, wavelets on water|
|6||25-31 mph||Strong, large branches move, umbrellas used with difficulty|
|7||32-38 mph||Near gale, whole trees in motion, fun walking into wind|
|8||39-46 mph||Gale, wind breaks twigs off trees, makes walking difficult|
|9||47-54 mph||Strong gale, slight damage occurs to building structures|
|10||55-63 mph||Storm, trees uprooted, considerable damage|
|11||64-72 mph||Violent storm, wide-spread damage|