When asking about a temperature inversion, and the flying conditions above and below it states that the air above the inversion is hotter than that below, meaning that it is also less dense. When descending into an inversion, the aeroplane will see an increase in lift, thrust and power.
However a radiation inversion is the opposite. The air is warmer below the inversion layer before conforming to its standard lapse rate above the inversion. Stated in the textbook, the temperature rises by about 10 degrees.
A lot of my questions that I have been asked just specify “what are the conditions below an inversion” and because of this I often get confused with what inversion they are referring to.
Or am I getting confused and below all inversions the performance will improve? I have had a look through all textbooks and resources available to me but I think I have just dug myself a hole.
Many thanks
PWMG
A temperature inversion means that temperature increases with height, so the air above the inversion is warmer and the air below it is cooler.
As the textbook explains, “warmer air sits above a colder layer” and this is called a temperature inversion. It also explains that the colder air is underneath because it is heavier, making the atmosphere very stable (CPL Meteorology, p. 47).
For a radiation inversion, the book says the surface cools at night, so the air near the ground becomes cold while the air above remains warmer. It specifically states: “Temperature is coldest at the surface and increases with height throughout the cold layer” (p. 47).
For a subsidence inversion, the textbook again describes cooler air below and warmer air above, with hazy and turbulent conditions below, and smooth clear conditions above (pp. 49–50).
Most importantly, the textbook gives the direct performance answer under Effects of an inversion on in-flight conditions:
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“When climbing through an inversion boundary, you will experience turbulence and decreased aircraft performance as you enter the warmer, less dense air above.” (p. 50)
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“When descending through an inversion boundary, you will experience turbulence and an increase in performance as you encounter cooler, denser air.” (p. 50)
So if an exam question simply asks “what are the conditions below an inversion?”, the safe textbook answer is:
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cooler air
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denser air
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often poorer visibility / haze and more turbulence
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better aircraft performance than above the inversion
The different types of inversion mainly describe how the inversion forms, not a different performance rule above and below it.
