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The jet stream

Full text: The jet streams are air currents of thousands of kilometers long, several hundred kilometers wide and several kilometers thick. This winds flow in a wavy west-to-east pattern at an altitude of about 10 to 15 kilometers. There are different types of this type of wind: there is, for example, a polar and a subtropical jet stream. Aircrafts fly exactly at the height of the jet stream. If they move to the east, they have tailwind and so they will fly much faster. Flights to the west often take longer for that reason; the plane has a headwind. The polar jet stream is created when warm air from the south collides with cold air from the north. The cold air sinks down, leaving few air particles higher up in the atmosphere. As a result, the warm air shifts towards the north over the cold air, to fill the shortage of air particles. The Coriolis effect causes the warm air to drift to the right, causing the jet stream to move eastward. This wind is therefore caused by the temperature difference between the north pole and the equator. Because this difference is greatest in the winter months, the wind is also strongest in winter. In summer, the temperature boundary between the warm and cold air is much more north and so is the jet stream. The jet stream has a major influence on the weather. The cold air from the north and the warm air from the south collide. Aloft, the jet stream flows to the east. But: In real life, the jet stream often has a wavy pattern. The strong wind aloft makes a turn. This means that a lot of air particles gather just before the turn, as if there are many cars in a traffic jam. These air particles sink to the bottom. Because more air particles are added than disappear at the surface, a high-pressure area is created at the surface. Just after the turn, the air particles move much faster at high altitudes. As if the cars can suddenly drive fast again after the traffic jam on a highway. Air particles are therefore sucked away. Because more air particles are removed than are added, a low-pressure area is created on the surface. The air rises, condensing water vapor and creating clouds and rain. The condensation of water vapor further heats up the air, making it warmer, rising faster and sucking new air at the surface. This low pressure area often follows the movement of the jet stream to the northeast. Eventually, cold air turns around the low-pressure area, stopping the flow of warm air, stopping precipitation and changing the weather. Thus, the jet stream is a strong wind aloft that can be found in different parts of the world and has great influence on the weather.