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4 Answers

does temperature inversion bring wind shear?

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Weather

Hi yall, I've always thought that whenever there's a temperature inversion, there's a high possibility of windshear.

But today I read in my ATP book it says,

"If the temperature actually increases as altitude increases, a temperature inversion exists. This is the most sable of weather conditions."

And before this paragraph it was about if temperature drops at a much faster rate than the normal lapse rate, the more unstable the air will be.

So, what is it that I'm not understanding? Eventhough the air can be stable, but there could be windshear?

 

I appreciate in advance for all the help!

Karl

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4 Answers



  1. Mark Kolber on Feb 16, 2016

    Perhaps you are not understanding the difference between an inversion in which the ambient temperature increases, instead of decreases, with altitude and a situation in which the temperature decreases faster than the lapse rate.

    This is a very simplistic picture of the more complicated “parcel theory” but I think it illustrates the point: Think of a small balloon that is filled with air that is kept exactly at the lapse rate temperature. What will it do when it is colder than the surrounding air? What will it do when it is warmer than the surrounding air? In the first situation, the parcel of stable air rises (just like thunderstorms develop). In the second, it doesn’t rise at all and may actually sink.

    It might help to picture how a hot air balloon rises and falls as you use the torch to increase its temperature and then let it cool.

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  2. Mark Kolber on Feb 16, 2016

    That was incomplete. Air stability is generally a vertical measure – how that balloon rises and falls. Wind shear is mostly a horizontal measure. That horizontal measure produces shear when the boundary line between the warmer air of the inversion and the colder non-inversion air is relatively small. It’s the change from one to another that contains the change in wind direction and intensity.

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  3. Tijmen de Boer on Feb 16, 2016

    Yes, it is a matter of density, thickness of the air. In fact all inversions give a kind of difference between windspeed and winddirection. Shears are often light, but may moderate ore more. The difference between convective or turbulence shears and this one, is that inversion shear stay at the same place and keep the same strengh for long time. So the inversion-shear is so to say stable😉 AND the air is very stable.
    Inversion shear are most hazardes near the surface and for the bigger planes, say wide bodies. We warn in aviation for strong low level inversions when they are more than 10 deg C below 1500 feet. Strong windshear is then possible and may be hazardous. Think of nice radiation weather in wintertime and warm air aloft.
    Gr Tim
    Senior aviation forecaster Amsterdam

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  4. Tijmen de Boer on Feb 16, 2016

    And not only the windshear can be hazardes, but also the T difference: when a heavy plane takes off and within say 300 feet the T rises 10+ degrees, the performance of the aircraft drops dramaticly…
    I haven often seen low level inversions of more than 10 degrees (10-15 degr max) in 500 feet!
    Gr Tim

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