Subsidence Inversions

  Subsidence Inversions Take pace in valleys or in places partially surrounded by hills or mountains.
  When the air blows over the hills, it is heated as it is compressed into the side of the hills
  When that warm air comes over the top, it is warmer than the cooler air of the valley.
  Also, increasing the inversion, as the air comes over the top of the hill, it causes the air in the valley to be compressed, heating the cooler, valley air from the top down.

picture by Amber Smith


  When this cool air is trapped and compressed, so is everything that is in the air, such as vehicle emissions, smoke, and smog in general. This is a big problem for cities located in valleys.  




Background photo from the University of Montana web site: