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When there is temperature inversion, I heard that convection is suppressed and hence the layer of air is stable.

But I also see the following questions when studying for my PAR:

  1. A pilot can expect a wind shear zone in a temperature inversion whenever the windspeed at 2000-4000ft above surface is at least 25 kts.

  2. Hazardous wind shear can occur near the ground with either thunderstorms or a strong temperature inversion.

  3. Hazardous wind shear can be expected in area of low level temperature inversion, frontal zones, and clean air turbulence.

  4. Smooth air, poor visibility, fog, haze, or low clouds should be expected beneath a low level temperature inversion layer when the relative humidity is high.

So is inversion good or bad?

A slightly related question: Possible mountain wave turbulence could be anticipated when winds of 40 knots or greater blow across a mountain ridge, and the air is unstable.

This leads me to believe that you can have turbulence while there is stable air. But I don't quite understand how. This seems contradicting to me. I'd not call air stable if there's turbulence. Can anyone shed light on this?

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    $\begingroup$ I would suggest breaking these into two separate questions as per the help center. The answer to each question is unrelated apart from being in the topic of meteorology $\endgroup$
    – Ben
    Jan 21 at 21:45
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    $\begingroup$ "Good" and "bad" are very subjective: If you get airsick and hate turbulence then smooth air is good. If you despise poorer visibility but don't mind getting bounced around then a more convective system might be to your liking. They also vary by degrees. $\endgroup$ Jan 22 at 0:02
  • $\begingroup$ "Is temperature inversion good or bad?" -- are you a glider pilot looking for good thermals, or looking for a smooth conditions for your first flight in a powered paraglider? $\endgroup$ Jan 23 at 12:24
  • $\begingroup$ "A slightly related question: Possible mountain wave turbulence could be anticipated when winds of 40 knots or greater blow across a mountain ridge, and the air is unstable." -- the accuracy of this statement, or lack thereof, would make a good ASE question. Mountain waves are in fact generally associated with a STABLE airmass. $\endgroup$ Jan 24 at 15:33
  • $\begingroup$ You could also ask a question about the specific meaning of the word "stable" in the context of the atmosphere. It has to do with the temperature lapse rate-- will a given parcel of rising air tend to stay warmer and less dense than the immediately surrounding airmass, or not. As you've noted in your question, certain kinds of turbulence are in fact associated with stable air. $\endgroup$ Jan 24 at 15:35

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To answer the first part, I wouldn't think of inversion being good or bad. It's just something that exists and a pilot should understand what it means. Inversion does have effect on weather and a/c performance, but you can't directly equate that to good or bad, it depends on the situation.

The second part, can turbulence exist in stable air? Most certainly yes it can.
Thermal turbulence, however doesn't. Thermal turbulence is the one you get when sun heats the ground and the adjacent warm air rises. This requires unstable or conditionally unstable air. However this is just one type of turbulence.

Stability of air mass would, with a fair amount of simplification, answer to a question "can thermal convection exist", but there are multiple other factors than thermal convection that cause turbulence.

Turbulence in general is a distrubed flow of air, very often caused by vertical currents disturbing the horizontal flow. In a mountain wave situation the wind sheering away from the mountain is deflected back towards the ground and stuck in a wave motion because of stability differences. This causes notable turbulence.

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Other types of turbulence you might find in stable air are mechanical (frictional) turbulence caused by objects such as buildings, coastlines or treelines, turbulence caused by wind direction or velocity changes in jetstreams. There's also almost always some turbulence at the tropopause level etc.

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