Wind is somewhat of a mystery. We can't see it, but we can feel it. So what exactly is wind?
Wind is the movement of large amounts of air. Even though we can't see air, we know that it is made up of molecules of different kinds of gasses, mostly nitrogen and oxygen. When lots of these molecules move, usually in one direction, we call this wind.
Where does wind come from?
Wind is caused by differences of pressure in the Earth's atmosphere. Air from a high pressure area will move towards an area of low pressure. High winds are caused when air moves between areas with large differences in air pressure.
On Earth, the main differences in air pressure are caused by differences in temperature. Cool air produces high air pressure and warm air produces low air pressure. Warm air wants to rise. When warm air rises, cool air will move in and replace the warm air, causing wind.
Another factor that affects the wind is the spinning of the Earth. This is called the Coriolis effect.
How is wind measured?
Meteorologists use two main measurements to describe wind: direction and speed.
Wind Direction - Wind direction is described by using the direction that the wind came from. For example, a southerly wind would blow from the south to the north. Wind direction is measured a number of ways including weather vanes, flags, and windsocks.
Wind Speed - The speed of wind is measured in miles per hour or kilometers per hour. Scientists typically use a tool called an anemometer to measure the speed of the wind.
Global Winds
The Earth has consistent wind patterns when looked at from a global scale. Global winds are created by both the spin of the Earth (Coriolis effect) and the differences in temperature between the equator and the polar areas. These winds are often grouped together as trade winds, easterlies, and westerlies.
Trade winds - Trade winds occur near the equator and flow from either the north or south towards the equator. They curve towards the west due to the spin of the Earth.
Prevailing westerlies - In the middle latitudes of the Earth, between 35 and 65 degrees latitude, are the prevailing westerly winds. These winds blow from the west to the east and also towards the poles.
Polar easterlies - These winds blow close to the north and south poles. They blow away from the poles and curve east to west.
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Local Winds
Some winds are generated by changes in air pressure and temperatures locally. These winds may change direction as conditions change throughout the day.
One example of a local wind is the wind that blows on the ocean coast. During the day, the land heats up faster than the ocean. This causes a "sea breeze" that blows from the ocean into the land. During the night, the land will cool down faster than the ocean and the opposite will occur. Warm air over the water will rise and cool air from the land, called a "land breeze", will blow out to the ocean.
Land formations such as mountains, valleys, lakes, and deserts can also effect the local wind conditions.
Wind Power
Wind is a great source of renewable energy. Wind turbines and wind farms can generate electricity without burning fossil fuels or producing pollution. You can learn more about this on our wind power page.
Interesting Facts about Wind
The fastest winds on Earth occur inside tornadoes where wind speeds can reach 250 miles per hour.
Meteorologists use barometers to measure air pressure. Barometers can tell us if the air pressure is dropping or rising.
The wind has helped to shape the land through the process of erosion.
Other planets with atmospheres have winds. Neptune has the highest speed sustained winds in the solar system with wind speeds of 1,300 miles per hour.
The solar wind is a stream of charged particles that flows from the Sun.
