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Do the clouds cause the turbulence or vice versa

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Do the clouds cause the turbulence or vice versa

Old 16th Jun 2018, 04:36
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Do the clouds cause the turbulence or vice versa

Seems more often than not that it is nice and smooth in cruise until one gets into the high level cloud tops. I guess meteorology was not my area of expertise in ground school so which one causes the other. Do the clouds cause the turbulence or the turbulence cause the clouds. Of course, the answer given might be, the mixing of air causes both. A lot of these sig Wx charts seem to like to call any high level turbulence area as CAT but it seems like the majority of the time when one encounters turbulence in these areas, the air is not clear where the worst of the turbulence is.
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Old 16th Jun 2018, 05:30
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Clouds are visual manifestations of underlying weather phenomena, and only appear when the relative humidity exceeds 100%, and condensation occurs.

There are a subset of phenomena such as strong thermals and CAT which may not involve clouds.

Thunderstorms are of course the most visible and extreme case, where ongoing condensation releases latent heat which prolongs the uplift, allowing the surface convection to reach the stratosphere.

There are also scenarios in which mountain wave turbulence produces alternate bands of clouds, in an atmosphere in which no thermals are present.

So, the answer is, its complicated!
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Old 16th Jun 2018, 08:22
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An excellent work called Aviation Weather from the FAA is available for free on the FAA site or you can buy a copy for a few dollars
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Old 16th Jun 2018, 10:32
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As I understand it; clouds form owing to the local humidity of the air and the presence of condensate nuclei - e.g. small particles of dust or similar?

I too have noticed that flying through some clouds in an otherwise smooth sky can result in sudden turbulence within the cloud but in others, not. I did wonder if this is due to the changes of density within the cloud affecting the lift produced by the wing but some clouds produce no turbulence at all, whereas others can produce catastrophic turbulence e.g. Cumulo Nimbus, which we all avoid of course.

Perhaps the reason is that some clouds, such as the CuNb also have strong updrafts but others, e.g. Cirrus have none, and only those clouds with updrafts produce turbulence?
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Old 16th Jun 2018, 19:28
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I used to teach Met in Vancouver, and this question reminds me of the hrs and hrs prepping for the endless stream of " Good Questions"
The answer : The egg came first!!
Not going there, sorry!

With regards to clear air turbulence it does fascinate me that I can ride a Jet-stream with 100kts for hrs with NO turb whatsoever.
And other times crossing an area with wind less then 15 kts with constant light chops.
Go figure.

OP, I bite. With the POTENTIAL for cloud , the mixing associated with turbulence will create the strati cloud.
A stratiform cloud does NOT necessarily equal turbulence.
A convective DOES , due updrafts, turbulent flow , and potential eventual downdrafts!
Class Dismissed.

( Note to self; Helmet, FLARE, Jamming ;ON . Transponder OFF, Dive for Cover!)
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Old 16th Jun 2018, 20:33
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OK, I should have been more clear. I am talking about the high altitude cirrus clouds. I guess I did basically say that so let's stick to the Cirrus.
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Old 16th Jun 2018, 21:55
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As I suggested, in the absence of convection, clouds do not cause anything. The answer to your original question is no, the turbulence is caused by other factors, mainly the jet stream.
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Old 16th Jun 2018, 22:13
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Air is always turbulent, sometimes more than other times, and is relevant to the ac. It is not a smooth flow, but flows in waves and currents, very similar to the Ocean, after all, air is just thin water....(it is called the jet STREAM)

The ac converts winds aloft into a 2D component representation, a direction and a speed.

It does not however, have a way to represent the vertical component of the winds...

OK, I should have been more clear. I am talking about the high altitude cirrus clouds. I guess I did basically say that so let's stick to the Cirrus.
in this scenario, clouds are the end result of atmospheric conditions, not the means.
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Old 17th Jun 2018, 00:11
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Key point about CIRRUS clouds, that make them different from other clouds. They are ICE clouds, not water-vapor clouds. Although obviously some super-cooled water vapor has to be there/get there in the beginning to freeze into ice. Being formed of ice crystals rather than water drops/vapor means they may follow different "rules" than other clouds. They can form even when the local humidity is low - aglomerating invisibly small amounts of water vapor (gas) into visible shapes. They form at higher altitudes than other clouds (although "higher" is relative - on cold days as low as 16000 feet.) They do not usually "precipitate out" as rain or snow, thus they are often "fair-weather" clouds - although they can also form and trail out from the super-cooled tops of Cbs or other bad weather.

Bottom line, as previously mentioned - cirrus clouds do not cause turbulence. They can be formed by turbulence and convection. Because of their longer-lasting nature, they may outlive the turbulence (if any) that formed them, and thus they are not necessarily a reliable indicator of the presence of current turbulence. However, they can increase the temperature of the air layer below them

Beyond that, we get into the physics of water phases (triple points, critical pressures/temperatures, specific heats, latent heats, phase changes, enthalpy of vaporization) that go far beyond "weather" per se. And my knowledge...
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Old 17th Jun 2018, 10:40
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Originally Posted by pattern_is_full View Post
Key point about CIRRUS clouds, that make them different from other clouds. They are ICE clouds, not water-vapor clouds......................Being formed of ice crystals rather than water drops/vapor means they may follow different "rules" than other clouds.........

Yes, good point.
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Old 18th Jun 2018, 07:49
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Originally Posted by GordonR_Cape View Post
As I suggested, in the absence of convection, clouds do not cause anything. The answer to your original question is no, the turbulence is caused by other factors, mainly the jet stream.
Why are the cloud tops in the FL300's always bumpy whilst the climb through the (Cirrus) cloud layer is stable and smooth?
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Old 18th Jun 2018, 09:05
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(ex) meteorologist here: Any cloud has the ability to generate turbulence as phase changes take out or add heat energy to the surrounding air creating density changes and therefore vertical motion; since it's not uniform across a cloud this generates turbulence. You get more 'bang for your buck' in liquid water clouds as condensation/evaporation is much faster than deposition/sublimation in ice clouds, and the amount of water vapour that air can hold (saturated vapour pressure) is much lower at lower temperatures (12hPa at +10C, 6hPa at 0C, 0.06hPa at -50C). Clouds of any nature will only form where the relative humidity is approx 100% and cirrus clouds can precipitate out (often seen as "mare's tails"), but will more often slowly sublime away.

Now the amount of turbulence associated with cirrus A versus cirrus B has a lot more to do with how it was formed; if it's associated with gentle uplift from a warm front several hundred nm away it might be smooth or turbulent depending where it is positioned relative to the jet stream, whereas if associated with the remnants of a CB it could be smooth or turbulent depending on the local flow and stability. So to the original question - "Do [high altitude] clouds cause turbulence, or vice-versa" the answer is a rather unsatisfying 'it depends....'
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