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In meteorology, air currents are concentrated areas of . They are mainly due to differences in atmospheric pressure or temperature. They are divided into horizontal and vertical currents; both are present at mesoscale while horizontal ones dominate at synoptic scale. Air currents are not only found in the troposphere, but extend to the stratosphere and mesosphere.
Pressure differences depend, in turn, on the average temperature in the air column. As the sun does not heat the Earth evenly, there is a temperature difference between the poles and the equator, creating air masses with more or less homogeneous temperature with latitude. Differences in atmospheric pressure are also at the origin of the general atmospheric circulation while the air masses are separated by ribbons where temperature changes rapidly. These are the fronts. Along these areas, higher winds aloft form. These horizontal jets (jet streams) can reach speeds of several hundred kilometers per hour and can span thousands of kilometers in length, but are narrow, having tens or hundreds of kilometers of width.
On the surface, the friction due to the terrain and other obstacles (buildings, trees, etc.) may contribute to a slowdown and/or a wind deflection. Thus, a more turbulent wind in the atmospheric boundary layer. This wind can be channeled through narrows, like valleys. The wind will also be raised along the slopes of the mountains to give local air currents.
On the other hand, barriers such as mountains force air up or down, sometimes rapidly. As the barriers are very localized, these currents will affect very limited areas and therefore will form corridors.
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