What causes wind to blow?

In this video we explain the science behind wind. What exactly is it and what causes it to blow?

Wind is air in motion, travelling between areas of different pressure.

To understand what causes this motion; we first need to understand a bit about air pressure.

When air heats up, the atoms and molecules within it move faster and spread out.

It is this reaction to heat that causes warm air to expand and rise,
In colder air the molecules move more slowly and are closer together, which makes the air sink.

When heat from the sun reflects off the Earth surface, it warms the air above it - this air will rise, leaving areas of lower pressure.

In contrast, areas of higher pressure occur where the cooler air is located.

When there is a difference in air pressure between two areas,
air moves from the high pressure area to low pressure area to equalise the pressure.

The best example of how this causes wind is in coastal areas.

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On sunny days, land warms up quicker than the sea, which reflects more of the sun’s rays.

This creates a temperature contrast and, as the land heats up, it warms and expands the air above it.

As this warm air expands, an area of low pressure is created over the land leaving relatively higher pressure over the sea. This pressure difference causes air to move from the sea to the land to equalise the pressure difference.

That rush of air is the wind we experience. In this case, a sea breeze.

Music by David Hyde