What Is Wind? Where Does Wind Come From?
What is wind exactly? Wind is the natural flow of air that we humans can detect. Wind is created when changes in temperatures cause air to move from high to low pressure areas. Low pressure areas are often where warm air is, because when air is warmed by the sun it rises, leaving behind less air, so there are fewer air molecules and therefore less pressure.
Air nearby with more molecules moves into lower pressure areas. So, in a sense, wind is created by our sun, because it heats some areas of the Earth’s surface more than others, thereby creating lower pressure systems. Wind speed is determined by how much of a difference there is in pressure between a low-pressure and high-pressure system. High-pressure systems usually contain air that is cooler and drier.
One way to measure wind is using the Beaufort Wind Scale which as made in 1805 by Sir Francis Beaufort, a member of the UK Royal Navy. It uses knots per hour though, which is slightly longer than one mile. The slowest breeze according to that system is 1–3 knots, and it is called a light breeze. A gentle breeze is air traveling at 7–10 knots and a moderate breeze is 17–21. From 22–27 knots is a strong breeze and 28–33 is a near gale. Beyond that are gale, strong gale, storm, violent storm, and hurricane, which has the fastest winds — 64 knots per hour or more.
Wind speed used to be measured with an anemometer. In 1934, a wind speed of 231 miles per hour was recorded. In a 1999 Oklahoma tornado, a wind speed of 318 miles per hour was recorded by Doppler radar. (The highest speed not connected with a tornado was 253 miles per hour.)
In the Northern Hemisphere, the Coriolis effect makes winds circulate in a clockwise direction, and in the Southern Hemisphere, a counterclockwise rotation.
You may have noticed that wind speeds are associated with terms like gale and storm, which denote weather which can be threatening or even harmful.
Prevailing winds are the dominant ones in their areas. For example, within the middle latitudes (35–65 degrees), the prevailing winds are called westerlies, because they blow frequently from the west to the east. These winds play a very important role in weather in certain areas, like the western coasts of continents.
You may have also heard of the trade winds, which are prevailing winds which blow from the northeast in the Northern Hemisphere and the southeast in the Southern. These winds are associated with sailing — particularly because they helped sailors travel from Europe to the Americas, as they were able to traverse the Pacific and Atlantic Oceans.
Wind also creates waves, so it again attracts the interest of sailors, and in this case surfers. Remember the Beaufort Wind Scale mentioned previously? It also describes the relationship between wind speed and wave speed. We have all seen calm water with a smooth surface and noticed there was no wind. A very slow wind of 1–3 knots only creates ripples or tiny waves. In fact, to get to small waves which are even 1 foot tall or up to four, wind speeds need to be about 11–16 knots. When that speed reaches 17–21 knots, waves may reach 4–8 feet in height and have many whitecaps. At 22–27 knots, waves 8–13 feet can be created. In near gale conditions with wind speeds of 28–33 knots, 13–19 foot waves occur. To reach 18–25 foot waves, wind speeds of 34–40 knots are required. From 41–47 knots, 23–32 foot waves are created. At 48–55 knots, 29–41 foot waves are created. At the extreme hurricane speeds over 64 knots, waves actually grow to over 45 feet. Wind plays a role in tornadoes, cyclones and hurricanes.
Wind plays a role in the formation of tornadoes. When it travels along the ground and then increases in speed and changes direction, it can enter unstable air created by a thunderstorm. The wind which was traveling across the ground then begins to tilt up and begins spinning. Eventually, it can become a rotating vertical column. Air which flows around the cyclone moves toward the thunderstorm and that contributes to the spinning of air as well.
So, the relationship between wind, weather, and waves has been touched upon, but there is something else wind does. Have you ever seen unusual or beautiful rock formations in natural areas and wondered how they were formed? If you guess wind and weathering, you were right.
Wind strikes rock formations over thousands of years or more and causes tiny bits of erosion that we would not be able to detect in a moment. However, when combined with dust, sand, and precipitation — plus many centuries — the effect is pronounced.
For example, a mushroom rock is exactly what the term sounds like, and it results precisely from this kind of wind effect.
(Rock formations can also result from the movement of water if the rocks were once underwater in a river, lake, pond, or even a sea.)
The consistent movement of wind against rocks, rock walls, cliffs, and outcroppings can shape them, but it also exposes different textures and layers, thereby adding some kind of aesthetic quality to the process. In fact, in some areas, the results on the rocks might actually appear to be intentional, though no human hand or plan was ever involved.
This fact might encourage us to wonder about different time scales on our planet and experience some detachment from the human time scale, so our problems or sufferings seem smaller by the comparison.
Places like Monument Valley in the United States have drawn droves of tourists and have been used in various movies as backgrounds and settings because they seem to bring out a sense of mystery and awe. For some people, these unusual rock formations and natural settings even have a spiritual connection, so they help reveal some sort of transcendence and perspective to them.
Sometimes the sound of wind is also something of a signal that breaks our habitual ways of perceiving things. In areas with beautiful, wind- and weather-sculpted rock formations, mountains and valleys, like Zion National Park and Park City, Utah, there are gatherings for flute makers and flute players.
Of course, humans for many centuries have been employing wind to turn windmills to make grain, pump water, and more recently to produce electricity.
Image Credit: Public Domain, Wiki Commons