What Causes Wind To Blow? Exploring the Factor That Affect the Horizontal Movement of Air

Wind is defined as the horizontal movement of air from one place to another. While low winds are less noticeable, forceful winds during inclement weather are obviously hard to ignore. There are days when there is a lot of wind, while there are times when there is nearly no wind. Technically speaking, wind is simply moving air caused by differences in air pressure.

What is Air Pressure?

The atoms and molecules that make up the air around us are constantly moving in random directions. Despite their tiny size, these particles have weight due to the pull of gravity. This means that the closer you get to the surface of the Earth, the more tightly packed the molecules are.

Gravity also makes the atoms and molecules press downward on whatever is below them. These particles exert a force on any surface that they strike into. The pressure exerted by air molecules is called atmospheric pressure, or air pressure. It is commonly measured with an instrument called a barometer and is expressed in a unit known as atmosphere (atm).

Each atom and molecule is too small to be felt and only exerts a tiny bit of force. However, we can get the sum of the total forces exerted by a large number of molecules that strike a surface each moment, then the total observed air pressure can be considerable.

What Causes Wind to Blow?

Wind exists due to the differences in air pressure which begins with the Sun. As sunlight reaches our planet, the Earth's surface is not heated equally. Sunlight strikes different places at different angles, creating unique degrees of warming. Some places like those in the equatorial regions receive more direct sunlight than polar regions, so they get warmer as a result.

As the Earth's surface warms, so does the air that touches it. In the places that warm more quickly, heat energy from the surface is transferred to the air molecules. At this point, the molecules get excited, so they spread out and rise. When the air gets warm enough, it becomes less dense and rises high into the sky, creating a low-pressure area.

On the other hand, cold air contains molecules that are more tightly packed. As these molecules sink downward, they exert a high amount of force onto the air below them. These areas are known to be centers of high pressure.

The Earth's atmosphere always seeks to maintain balance, but some areas have more air pressure than others. In an attempt to equalize these differences, air molecules from areas of high pressure always move to the areas of low pressure. This naturally happens to fill the space left behind by the warm, rising air.

Meteorologists call this the "pressure gradient force", or the force that pushes air horizontally between high and low-pressure regions. At this point, wind is created as a result of the rush of air between these two locations.

The speed of the wind is determined by the amount of pressure difference that exists. The greater the differences in pressure, the faster the air flows towards the low pressure area. Meanwhile, the direction to which the wind blows is determined by position of the high and low pressure areas, and by the Coriolis Effect which refers to the deflection of circulating air due to the rotation of the Earth.