WIND

Wind is the movement of the atmosphere. The atmosphere moves because the Sun heats the Earth’s surface, causing air to increase in temperature, expand, and rise upwards. Cool air moves in to replace the warm air, and we feel this movement of air as wind. The air flows from areas of high pressure to areas of low pressure around the globe. The strongest winds occur during HURRICANES and TORNADOES.

WHERE THE WIND BLOWS

At the Earth’s poles, the air is at high pressure and low temperature; at the Equator, it is at low pressure but higher temperature. This, together with the spin of the Earth on its axis, creates a pattern of warm and cool winds around the globe. Continents and high mountains also produce wind patterns, such as the monsoon winds over southern Asia. Areas on the Equator where the winds are very light are called the doldrums. Sailing ships used to get stuck there for long periods.

PREVAILING WIND

Winds often blow from one direction most of the time. If these prevailing winds are strong, trees grow lopsided. Wind direction is always given by the direction the wind is blowing from, rather than where it is blowing to. A southerly wind, for example, blows from the south towards the north. Wind speed is measured in kph or mph. At sea, it is measured on the Beaufort Scale, from force zero (no wind) to force 12 (hurricane).

HURRICANE

A hurricane is a huge, spinning storm with very high-speed winds. A hurricane starts life as a group of thunderstorms near the Equator. If the storms begin to spin together, they form a tropical storm. If the storm’s winds reach more than 119 kph (74 mph), it is called a hurricane. In the Pacific Ocean, hurricanes are called typhoons; in the Indian Ocean, they are called cyclones.

INSIDE A HURRICANE

A hurricane contains spiral bands of thunderstorms spinning around a still centre called the eye. Warm air within the bands flows around the eye and upwards. The air pressure in the eye is so low that, over sea, water bulges upwards. If the hurricane hits land, the bulge turns to a mass of water that floods the coast in a storm surge.

EYE OF THE STORM

The central eye and swirling storm clouds of a hurricane can be seen in a satellite image taken high above the Earth. The hurricane’s strongest winds are in the eye wall (the towering wall of cloud around the eye). These often reach speeds of 300 kph (190 mph). Inside the eye, however, there is almost no wind. The eye is usually between 8 and 25 km (5 and 15 miles) in diameter. The hurricane itself can be up to 800 km (500 miles) across.

TORNADO

A tornado is a spinning, funnel-shaped column of air. Inside, winds can blow at speeds of more than 480 kph (300 mph) – the fastest winds on Earth. These violent winds destroy buildings in their path. Tornadoes form underneath giant thunderstorms, and they can be anything from a few metres to 800 m (half a mile) across. Most tornadoes happen in the USA, especially in Tornado Alley in central USA.

Copyright © 2007 Dorling Kindersley

stay connected

Sign up for our free email newsletters and receive the latest advice and information on all things parenting.

Enter your email address to sign up or manage your account.

Facebook icon Twitter icon Follow Us on Pinterest

editor’s picks

highlights

12 Pumpkin Activities and Crafts for Kids
Pumpkins and gourds are perfect for fall fun and games with the kids. Find the best pumpkin activities, crafts, printables, and recipes to enjoy with your children this Halloween season.

Kindergarten Readiness App Wins Gold
Our Kindergarten Readiness app won the Gold Award of Excellence in the educational category at the 2014 Communicator Awards. This valuable checklist comes with games and activities to help your child practice the essential skills she needs for kindergarten. Download the Kindergarten Readiness app today!

15 Best Slow Cooker Meals
Too busy to cook? Try one of these deliciously easy slow cooker meals and have dinner waiting when you get home!

Find Today's Newest & Best Children's Books!
Looking for newly released books for your child? Try our new Book Finder tool to search for new books by age, type, and theme, and create reading lists for kids!