If you spend any time studying meteorology, you might have heard about a phenomenon called the jet stream. One of Earth’s most prominent examples of this phenomenon is the polar jet stream. The polar jet stream is a current of flowing air that is powerful enough to affect weather patterns in the entire Northern Hemisphere!
What’s more, the Southern Hemisphere has its own polar jet stream. And, while that stream doesn’t affect weather in the Northern Hemisphere, it still has a huge impact on the weather patterns of regions like South America, South Africa, and Australia!
What Causes the Jet Stream?
Jet streams are caused by a combination of physical factors. The first, and most obvious, is the uneven heating of the planet. Since Earth sits at a slight angle on its axis, in relation to the sun, the planet is cooked unevenly by the sun’s rays. This, in turn, leads to the planet’s weather as we know it. Everything from the seasons to the movement of the currents in the air above us is related to this uneven heating.
The other factor that leads to the creation of the jet stream, ironically enough, is another side-effect of the planet’s axis. However, this second force would be in effect even if the Earth wasn’t slightly offset compared to the sun. It’s the Coriolis force, a complicated physical phenomenon that is best explained with an example.
The Coriolis Force
The Earth is rotating all the time. This rotation creates the day and night cycle that people on the surface of the planet observe as the objects around us moving, and we don’t perceive the planet itself moving from our perspective. However, if you get into a plane and head north from Florida to New York, suddenly you’re no longer gravitationally bound to the ground, and, from space, your vehicle would appear to move north and north-easterly at the same time.
This is because the planet under the plane is still rotating, but the plane is under a much weaker version of the Coriolis effect. This force, the planet spinning and the air above it being dragged along by gravity leads to the creation of many jet streams, including the polar jets that so profoundly affect weather around the world.
Boundary and Courier
The jet stream at the North Pole keeps the Arctic weather bounded in. The fast-moving current of the jet stream typically prevents the cold air from seeping to the south, creating the weather pattern that we recognize in the Northern Hemisphere, where areas that are farther north are colder, and vice versa.
When the jet stream weakens or dips to the south, it creates bizarre weather patterns, like cold snaps in southern areas or unseasonable wet and dry seasons at the coasts of some continents. The jet stream is so important for the seasons and climate of the planet that slight variations in its strength and position can result in things like intensely cold winters, massive increases in rainfall, and even increased storm activity.
In this way, the jet stream acts as both a boundary for the polar ice cap and a courier of weather patterns, carrying far-flung storm fronts across the globe.
