WHY DOES THE WIND BLOW?

Picture of why the wind blows

Why does the wind blow? 🌬

Sun rays pass through the different layers of the atmosphere and heat the surface of the Earth. The air itself is heated mostly not directly by the Sun, but by the warmed surface of the Earth.

The atmosphere can be imagined as a very thin shell surrounding the Earth, like a film. This shell has different layers. In one of the upper layers there is the ozone layer, which protects the Earth from harmful ultraviolet radiation from the Sun.

Air is a mixture of gases. It consists of about 78% nitrogen, about 21% oxygen, and about 1% other gases (argon, carbon dioxide, water vapor, and others). Interestingly, carbon dioxide makes up only about 0.03–0.04% of the air. Most of the air is found in the lower part of the atmosphere — roughly within the first 15–20 kilometers above the Earth's surface.

The Sun heats different parts of the Earth's surface unevenly. This happens because of clouds, features of the Earth's surface, and the different angles at which sunlight reaches the ground. Because of this, the air temperature becomes different in different places. This creates a difference in atmospheric pressure.

When air warms up, its molecules begin to move faster and the air expands. As a result, the density of the air decreases— there are fewer molecules in the same volume. Therefore, pressure becomes lower in warmer areas. In colder areas the air is denser, so the pressure there is higher.

According to the laws of physics, the atmosphere tries to equalize this pressure difference. Pressure always tends toward balance. Therefore, air begins to move from areas of higher pressure (usually colder areas) to areas of lower pressure.

This movement of air is called wind.

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