Aerodynamic and Exhaust Mediated Persistent Contrails - When do they Form?

George B

Extinct but not forgotten Staff Member
I don't think there are significant atmospheric changes for contrail formation or persistence.
Temperature is up by about 0.8°C, mostly in recent decades. I don't think this means much in terms of the height of the -40°C isotherm.
As far as I know, there is no change in the RH (not the same as water vapor content).

The question involves memory, storage efficiency, recollection accuracy, conscious interest, and other qualitative influences.
When you started this line of questioning, you didn't mention we were dealing with immeasurable organic factors like memory.

As Mick says, the reasons are about changes in the aviation industry. Memory for this type of thing is very unreliable, as we have seen. For instance, the first persistent contrail I recall noticing was in about 2002. I started in meteorology in 1977. You would think that I would recall seeing one before 2002, but I don't. No shame; not unprofessional; poor memory. Pfft. There is plenty of reliable actual documentation to rely on, though.

Good grief!
I have not said one thing about possible atmospheric changes increasing contrail formation . . . I am not asking if more traffic increases RH or nuclei or if climate change is increasing RH at higher altitudes and thus increasing persistent contrail formation . . . I am asking the following . . .


1) Do you or do you not think the fact more aircraft are capable of flying above 28,000 feet has increased persistent contrails formation over previous decades primarily because they are transversing colder temperatures than they would at lower cruising altitudes ?

2) or do you think the greater number of contrails is due primarily to the faulty memory of people and that there are simply more aircraft flying at all altitudes ?
 
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Pete

Member
I genuinely struggle to discuss/argue about chemtrails now. If you still believe in chemtrails (or as I now call them, chemtrials) then there is no changing your mind. Believer's just want to believe and us sensible folk are just wasting our breath (pun). Or we are "shills", but then I guess paid for "shills" wouldn't just give up.

They are contrails. They happen when the conditions are correct. The weather up there is different to down here and can change very rapidly as the air is often moving at 100s of mph... Photographic evidence proves persistent contrails existed many years ago. Enough already.

Cheers to Mick to having the patience of a saint.
 

MikeC

Closed Account
Then you have totally lost me . . . seems the higher altitudes have a greater chance of below freezing temperatures . . . so it is logical persistent contrails have a much better chance to form at 28,000 feet than at 5,000 feet . . . assuming RH is the same in both places . . .

What he was saying is that contrails are not a matter of CHANCE.

They are a matter of physics.

the required low temperatures occur more often at altitude on a worldwide basis - but contrails will form wherever those conditions exist, regardless of altitude. At ground level they sometimes exist in the polar - hence you sometimes get engine-contrails at takeoff eg see here

Physics does not roll dice or flip coins - conditions are either right for contrails or they are not.
 

Ross Marsden

Senior Member.
I have not said one thing about possible atmospheric changes increasing contrail formation . . . I am not asking if more traffic increases RH or nuclei or if climate change is increasing RH at higher altitudes and thus increasing persistent contrail formation . . . I am asking the following . . .


1) Do you or do you not think the fact more aircraft are capable of flying above 28,000 feet has increased persistent contrails formation over previous decades primarily because they are transversing colder temperatures than they would at lower cruising altitudes ?

2) or do you think the greater number of contrails is due primarily to the faulty memory of people and that there are simply more aircraft flying at all altitudes ?

Oh, OK, I appoligise I misread your post. Sorry; wrong direction, but good to have covered that off.
Well, your first question has evolved into one about the deployment of aircraft types with unvarying (generally increasing, up to a point) cruise altitude ceilings. I don't feel qualified (or knowledgeable) enough to answer that except in pretty vague terms. The question is still about the inquirer's memory since since they are probably not presenting you with research containing quantitative data about the occurrence and geographical distribution of contrails.

The second question is about the perceived greater number of contrails. The increase in that number is due to the memory thing as well as the actual increase in occurrence due to changes in air transport engineering, routing and flight frequency.

The contrail altitude can easily be lower than 28000 feet. In the vicinity of Nottingham, UK on 29 Dec 2013, the lower bound was 23,500 feet for ephemeral contrails and 24,600 for persistent contrails. As well as that, air craft were photographed making aerodynamic contrails lower than that - 18900 to 22000 feet. See this chart:

Nottingham_20131229_amMidnight_hb.PNG

The vertical black bars at the right indicate the ice-supersaturated layers indicated by the data from this sounding.
 

George B

Extinct but not forgotten Staff Member
Oh, OK, I appoligise I misread your post. Sorry; wrong direction, but good to have covered that off.
Well, your first question has evolved into one about the deployment of aircraft types with unvarying (generally increasing, up to a point) cruise altitude ceilings. I don't feel qualified (or knowledgeable) enough to answer that except in pretty vague terms. The question is still about the inquirer's memory since since they are probably not presenting you with research containing quantitative data about the occurrence and geographical distribution of contrails.

The second question is about the perceived greater number of contrails. The increase in that number is due to the memory thing as well as the actual increase in occurrence due to changes in air transport engineering, routing and flight frequency.

The contrail altitude can easily be lower than 28000 feet. In the vicinity of Nottingham, UK on 29 Dec 2013, the lower bound was 23,500 feet for ephemeral contrails and 24,600 for persistent contrails. As well as that, air craft were photographed making aerodynamic contrails lower than that - 18900 to 22000 feet. See this chart:

Nottingham_20131229_amMidnight_hb.PNG

The vertical black bars at the right indicate the ice-supersaturated layers indicated by the data from this sounding.
Good . . . now that we have established persistent contrails may form at cruising altitudes and in the case of more northern latitudes and probably at southern most latitudes as well . . . and as in the case you cited above as low as 24,600 feet for persistent contrails . . . so can we say at least hypothetically for exhaust mediated persistent contrails when RH is constant at all altitudes, Temperature is then the controlling major factor which determines if persistent contrails may form ?

And if this is correct . . . can then a general statement be made that when aircraft fly above 24,600 feet there is a higher chance they may propagate persistent exhaust mediated contrails than if they were flying below 23,000 feet?
 

Pete

Member
And if this is correct . . . can then a general statement be made that when aircraft fly above 24,600 feet there is a higher chance they may propagate persistent exhaust mediated contrails than if they were flying below 23,000 feet?

Generally the higher you go, the colder it gets, so the more likely the conditions will be good for persistent contrails... But relative humidity is also rather important at the time aircraft flies through. But so what? Weren't you discussing this point 6 months ago? Lay down your point and try to prove it, stop beating around 1000 bushes.
 

Jazzy

Closed Account
can then a general statement be made that when aircraft fly above 24,600 feet there is a higher chance they may propagate persistent exhaust mediated contrails than if they were flying below 23,000 feet?
Only with respect to the mid-latitudes.

The bulk of the atmosphere is oblate, like the earth itself, and the equivalent altitudes at equator and poles are respectively higher and lower.

As Albert said (approximately), "Explanations must be as simple as possible. But not simpler."
 

George B

Extinct but not forgotten Staff Member
Generally the higher you go, the colder it gets, so the more likely the conditions will be good for persistent contrails... But relative humidity is also rather important at the time aircraft flies through. But so what? Weren't you discussing this point 6 months ago? Lay down your point and try to prove it, stop beating around 1000 bushes.
I am making no point . . . I am trying from the first post above to get a general statement from the experts here under what general conditions (most specifically altitude which is more closely related to temperature) one would expect aerodynamic mediated persistent contrails to propagate (where RH is not a factor at any specific altitude) versus those conditions (specifically altitude) for primarily exhaust mediated persistent contrails . . .
 

George B

Extinct but not forgotten Staff Member
Only with respect to the mid-latitudes.

The bulk of the atmosphere is oblate, like the earth itself, and the equivalent altitudes at equator and poles are respectively higher and lower.

As Albert said (approximately), "Explanations must be as simple as possible. But not simpler."
I realize the atmospheric conditions at the equator and depth of the atmosphere, height of troposphere, etc is different than in the temperate , and polar zones . . . I am seeking general probabilities for primarily the zone where the majority of Chemtrail believers reside which I conclude is in primarily the temperate zones . . .
 

Mick West

Administrator
Staff member
I am making no point . . . I am trying from the first post above to get a general statement from the experts here under what general conditions (most specifically altitude which is more closely related to temperature) one would expect aerodynamic mediated persistent contrails to propagate (where RH is not a factor at any specific altitude) versus those conditions (specifically altitude) for primarily exhaust mediated persistent contrails . . .

I think you'd be best served by looking into the difference between the two in terms of physics. Otherwise it's just an argument from authority. See attached.

The vast majority of contrails you see are exhaust contrails. The vast majority (if not all, for you) are high altitude, above 28,000 feet.

Most aerodynamic contrails are water droplets, and generally do not persist or propagate. Ice aerodynamic persistent contrails are rare compared to persistent exhaust contrails - especially in a clear sky. I have never seen something that looked like an aerodynamic contrail persist and spread. The only reason they factor into the "chemtrail" discussion is that they look like they are coming from the whole wing, and so make impressive video.
 

Attachments

  • acpd-13-14667-2013.pdf
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George B

Extinct but not forgotten Staff Member
Mick, thanks for the rescue the information you provided is almost as I expected . . . seems aerodynamic mediated persistent contrails are rare and while possible are likely not a factor in the misidentification issues with Chemtrail advocates . . . Thanks!;)
 

Ross Marsden

Senior Member.
I'm more inclined to agree with Mick's summary. While comparatively rare, aerodynamic contrails are observed, and do get folded into the chemtrail narrative. An important feature of them is their comparative low altitude, and attract special attention because of that.

On the other hand, they are not as voluminous, do not remain visible for as long, and are not as prone to spreading as exhaust contrails.
 

Jay Reynolds

Senior Member.
It really does boil down to memory. Ask most chemtrail believers when "chemtrails" first started in their particular area and they will invariably come up with a date for when they first noticed them. Go to the chemtrailcentral.com forum which began ops in 2000 and you will most certainly find other people in the same area who noticed them many years earlier. I did this recently with Joe, and the result was about 7 years as I recall.

Just about every day, people notice them for the very first time, while others noticed them years before. Dr. Patrick Minnis, one of the ost published US contrail/cirrus expers told me he personally experienced the same thing.

BTW, part of the early history of the chemtrails hoax featured the idea of a "MEGASPRAYER", planes which made wingspan wide aerodynamic contrails.
prototypically the idea was promoted by a website called "Megasprayer News". The inception of the gambit was a photo of wingspan aerodynamic contrails which you can find at Carnicom's site.

Megasprayer news ended up being a chemtrail believer only message board at this URL:
http://chem11.proboards.com/

Last I checked, there was ~maybe~ one poster "Big Bunny" who had made it his homestead for posting fear porn......other members once quite active have all moved on, including the site owner "Chem11" who was a very prolific chemtrals promoter who seemed to simply 'poof' and disappear about 2006/7 soon after figuring out that the planes people were seeing were not "Megasprayers", but rather ordinary commercial flights .
 
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