Winds can occur on many different scales. However, there is a consistent pattern to how air moves on a big scale. This pattern acts as a global air conditioner, and it's the reason that we are able to live on the earth.

In this video, we will take a look at what we call the global wind circulation.

The global wind circulation gets its power from two sources:
Heat and the rotation of the earth.

Let's take a look at heat. The sun constantly sends heat energy towards the earth in the form of radiation.

By the equator the energy is highest because the sun hits the surface more concentrated here than by the poles.

This results in big temperature differences, and the global wind circulation contributes to even out these differences. In this way, it acts like a global air conditioning system.

At the equator, hot air rises while the cold air sinks to the surface closer to the poles. To even out the difference, the hot air from the Equator moves to the poles, – while cold air from the poles travels to the equator. From here, the pattern repeats. This is what would happen if the earth wasn't moving and if there were no oceans, but obviously, it's not that simple.

As the earth rotates on its own axis, the Coriolis effect occurs. It's a very complicated topic, – but it basically has to do with the rotation of the earth and the fact that it's wider at the equator, meaning the air has to travel further than by the poles.

This means that air does not travel directly from equator to the poles. Instead, air blowing towards the poles, flows eastwards while air traveling back to the equator turns to the west.

Because of this, air moves in three circulation cells in both the northern and the southern hemispheres – instead of moving in just one big circulation pattern.

One of the consistent wind patterns we see on a global scale is jet streams. These are powerful winds at an altitude of around 11 kilometers that blow from west to east. The jet streams are known for giving airplanes a time saving boost when they travel from the US to Europe. Furthermore, they strongly influence the weather because they are strong enough to move underlying weather systems.

The patterns of these jet stream change - shifting its pattern from zonal to merigional. The three cell model can also help us understand why specific latitudes have rainforests and some have deserts.

If we look between each cell, we have air that’s either rising or sinking giving us our climatic zones.

In the areas where air is rising we have more rainfall. This is why there are many rainforests near the equator. Desert regions, however, are typically located in areas where air is descending, creating high pressure to the surface and thereby clear skies and little rainfall. The three cell model is a simplified theoretical tool, but it's not perfect. For instance, the model ignores the effect of continents, mountains and sea currents.

Now we've learned the basics about global wind patterns. In the next video, we will look at precipitation and weather fronts.