Inversions

[Ref Understanding Weather & Climate, Books a la Carte Edition (6th Edition) #ISBN-13: 978-0321773227 #ISBN-10: 0321773225 CH 6 Cloud Development and Forms, PPL Instruction Kit Vol2 (306) – 9th Edition, V9.2 P.568-570]

Inversions

Inversions – temperature of the ambient air increases with altitude

There are 4 types of inversions:

  1. Radiation inversion (i.e Surface-based temperature inversions)
    • results from diabatic cooling
    • associate with radiation fog on the ground level
      (usually occur on clear, cool nights, with relatively little to no wind present)
  2. Frontal inversions
  3. Subsidence inversions ( Turbulence Inversion)
  4. Turbulence inversion
    • usually dry air with turbulence AND close to the ground
    • the parcel of air forced downward, it will has higher temperature – refer to DALR

Features and related WX of temperature Inversion (Layer)

  1. Density
    • Hot air, Air density lower – decreasing air density during climbing – lift and power may reduce.
  2. Visibility
    • Below the inversion layer, lack of (not enough) convection – pollution is trapped
    • If the relative humidity of the air is high, it can contribute to the formation of clouds, fog, haze, or smoke
  3. Turbulence and Change in Wind direction
    • below the inversion layer is smooth, stable air, but wind shear is expected at the upper boundary of the layer.
  4. Source: https://www.aopa.org/news-and-media/all-news/2010/november/01/wx-watch-freezing-rain-facts

    Ice pellets – temperature inversion at higher altitude

    • Ice pellets are an indication of a temperature inversion and that freezing rain exists at a higher altitude
      (Ice pellets are formed because rain falls through a temperature inversion, the rain may freeze as it passes through the underlying cold air and fall to the ground in the form of ice pellets)

 

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