Kids ask: How does the wind blow?

Tony Neuman, 8, a third-grader at Prairieview School in Hainesville, asked, "How does wind blow?"

Without air, there's no wind. Without the Sun, there's no wind. Without the Earth's rotation, there's no wind. So what is wind?

Air is a mix of gasses that blanket our planet. Air is also called atmosphere. Closer to sea level, there's high air pressure - 14.7 pounds per square inch. At the top of a mountain, for example, one that's 20,000 feet high, the air pressure is low - 6.7 pounds per square inch. The two forces try to seek a balance with the high moving to the low. That's called pressure gradient, and that's what starts air in motion.

"Wind is essentially created from a pressure gradient, meaning there is a change is pressure throughout an area," said Blake Hamilton, a senior meteorology student at Iowa State University.

Even if it's a beach day at the bottom of the mountain, there might be snow at the top. High pressure at the bottom of the mountain means warmer temperatures, and low air pressure at the top of the mountain means colder temperatures.

Other things push air into motion. The Sun's energy is not absorbed evenly across the Earth's surface. At the top of a mountain it might be sunny, but shadows from mountain peaks might stop sunlight from covering the valley below. In a desert, a lot of sunlight is absorbed, but at night it becomes very cool since there are no clouds to keep in the heat. This uneven energy from the sun creates different temperatures, and the mixing of different temperatures also creates wind.

The Earth spins as it orbits the Sun. Spin and rotation are the same. The Earth's rotation creates air movement. Natural features, like mountains and valleys, force changes in air movement.

Air, pressure gradient, the Sun, the Earth's rotation and the natural features on the Earth's surface all make wind. Some winds occur in the same place over and over, so they have special names. Maybe you've heard of the Santa Ana winds in Southern California or the doldrums near the equator.

Meteorologists use an anemometer to measure wind. Hamilton described how you can look at a weather map and forecast wind changes.

"When looking at a basic surface weather map, you can see many lines labeled as areas of equal pressure called isobars," he said. "When these lines are close together, that means the pressure is changing rather fast in a small area. Generally, the closer these lines are, the higher the wind speed."

Wind is a powerful force that is used to create energy. Wind mills have been used for centuries to drive pumps that move water or machinery. Giant wind turbines, which look like wind mills, are used to create electricity that is nonpolluting and inexpensive.

Send in your question

Be the one who creates the news. What's the farthest galaxy? Who is the most famous ballplayer? Find out more about oceans, history, geography, ecology or anything at all by sending your question to kidsink@dailyherald.com. Include your name, age, hometown, grade and school. Teacher packets available on request.

Check these out

The Grayslake Area Library has these suggestions for more information on wind:

• Weather web site for kids: www.wildwildweather.com

• "I Face the Wind," by Vicki Cobb

• "Wind," by Ann Herriges

• "Wind," by Terri Sievert

• "Mirandy and Brother Wind," by Patricia C. McKissack