[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
   • results from a warm front over a cold air mass
3. Subsidence inversions (≠ Turbulence Inversion)
   • associate with high pressure system
   • the parcel of air sinking (subsiding), it encounters with compression and the temperature increases
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. 

   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)