March 12, 2013
What is Wind?
Hi, my name is Emerald Robinson, and in this “What is” video, we’re going to examine the force that we call wind.
Wind is defined as “gas in motion.” Although wind is usually moving air on earth, wind in outer space can be highly charged gases called plasma moving away from a star, or hydrogen escaping from the atmosphere of a planet.
On earth, we classify winds by two main characteristics:
● their strength, that is, how fast and with how much force they blow, and
● their direction, which we name by finding the direction from which the wind originates. For example, “North” winds blow from north to south.
Anemometers determine wind speed, which is measured in a unit equal to 1.15 miles per hour, called a “knot.” Sustained winds are graded on the Beaufort number scale. Gentle breezes of less than 27 knots earn numbers between 1 and 6, while hurricane gales of over 120 knots qualify for a 17.
Wind is produced when the earth’s surface is not heated evenly by the sun. Air over warm earth rises and causes an updraft. When this happens, cooler air rushes in to fill the space left behind. The stronger the updraft, the stronger the wind.
Since air over land heats up and cools down more rapidly than air over water, there is almost always wind near lakes and oceans.
Winds have a large impact on the earth. Winds carry atmospheric moisture from place to place, causing rain. The strong winds of hurricanes and tornadoes cause tremendous amounts of damage, and winds erode land forms as well as sculpt the faces of mountains.
Humans have learned to harness wind power for many uses. Wind drives large turbines that make electricity, and wind fills the sails of ships. We even use wind for recreation, as it enables us to fly kites, para-sail, and hang glide.