page_title: Air current
section_title: Mechanically induced
hierarchical_section_title: Air current / Vertical currents / Mechanically induced
context_page_description: Air currents are concentrated areas of winds. They are mainly due to differences in 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.
context_section_description: In an air mass moving, vertical movements occur when there is convergence and divergence at different levels of the atmosphere. For example, when we are near the jet stream, winds increase when approaching its most intense region and decreases when it moves away. So there are areas where the air accumulates and must come down, while in other areas there is a loss and an updraft from lower layers. These upward or downward flows will be relatively diffused.
  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.
caption: Foehn wind diagram.
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