Spectrar Ghost
Senior Member.
Based on context I'd presume it's a reduction in surface temperature of 0.159C.
Debunking "Contrails don't Persist" with a Study of 70 Years of Books on Clouds
- Thread starter Mick West
- Start date
Based on context I'd presume it's a reduction in surface temperature of 0.159C.
Graham2001
Active Member
A 1905 book on clouds has been uploaded to Project Gutenberg, the scans of the illustrations are not perfect, but the show quite clearly that clouds back then look like clouds now.
Cloud Studies by Arthur W. Clayden (1905)
http://www.gutenberg.org/ebooks/55126
The authors introduction recommends the book to meteorologists, artists and anyone who is interested in the sky.
Cloud Studies by Arthur W. Clayden (1905)
http://www.gutenberg.org/ebooks/55126
The authors introduction recommends the book to meteorologists, artists and anyone who is interested in the sky.
SR1419
Senior Member.
Mick has been using that books for years: http://contrailscience.com/clouds-before-planes-cloud-studies-1905/
Its also on Archive.org
https://ia600201.us.archive.org/27/items/cu31924002961203/cu31924002961203.pdf
can persist for hours - --
I'm not sure that a few hours, but I'm sure that I watched 30-40 minutes ..
everything depends on the weather and the airplane.
To see them persist for hours you usually have to look at satellite image, as the wind has generally carried them out of view after a couple of hours. They also spread out, and it's hard to distinguish them from other clouds.
I think more commonly people see contrail cover that last hours, and don't realize it's from different contrails. Like:
Source: https://www.youtube.com/watch?v=kQekGClN5GE
There are many things to consider when talking about contrail formation. Just off the top of my head, and not in any particular order:
1. Atmospheric profile (temperature, humidity, and pressure with respect to height.)
2. Partial vapour pressure with respect to ice.
3. Partial vapour pressure with respect to water.
4. Condensation (or sublimation) nuclei.
5. Cosmic radiation levels.
6. Fuel and exhaust gas composition.
7. Aircraft velocity.
8. Aircraft elevation.
9. Aircraft type
10. Engine types and configuration.
11. Wake turbulence.
12. Exhaust turbulence.
13. Exhaust velocity and volume.
14. Atmospheric winds
15. Season
16. Time of day
17. Latitude and longtitude
16. Angle of view
17. Sizes, shapes, and properties of constituent water droplets or ice crystals.
18. Additional layers of clouds or contrails)
.
Remember that all of these things determine what a contrail will look like from the ground. You cannot start with the "look" of or shape of a contrail and make statements about what all the determining factors are. That is pure silliness and is a trap that many fall into.
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This has been posted before, but the version I saw before was the reprint without the last paragraph. This is the original, from:
https://books.google.com/books?id=N...ts=bpfzssIufW&pg=RA4-PA13#v=onepage&q&f=false
It's interesting because even back then, in the very first few times that planes had flown at that altitude, the causes of contrail cloud formation were broadly understood.
Cloud Formation by Supercharged Plane
An altitude flight was made in the morning at McCook Field, recently, by Lieut. J. A. Macready in a LePere with supercharged Liberty. When the airplane reached a height of 26—27,000 feet at 11.50 a. m., a long feathery white streamer was observed forming behind a rapidly moving dark speck. The cloud was of the cirrus variety, well defined at its edges and apparently ten to fifteen times the width of the plane. The sky behind the first portion was clear blue with no other clouds in the near neighborhood. The first streamer seemed perhaps two miles long. Then a gap of one-quarter mile. The second streamer formed with a background of light cirrus cloud and after two or three miles the plane seemed to go into the cirrus background for the streamer formation ceased while an apparent path of blue continued beyond for a way in the cirrus cloud. The whole streamer may have been three miles long. After twenty minutes the streamer had drifted and spread until it merged indistinguishably with the other cirrus clouds visible. The weather conditions at the time were generally very clear, warm, with perhaps 0.1 of the sky in cirrus clouds.
The observer reported as having observed nothing unusual; occasionally the motor would give a burst of black exhaust gas. The pilot thought he remembered having passed through a stratum that felt damp. Clouds at this altitude are necessarily ice crystals, or needles, and it is difficult to determine the cause of the cloud formation under consideration. Possible contributing causes are: Water in exhaust; dust and carbon particles in exhaust serving as cloud nuclei; convective currents due to disturbance caused by passage of plane. Conditions of humidity were undoubtedly ideal for the formation of cloud at that altitude.
SR1419
Senior Member.
That description has it all; persisting, spreading, gaps...even a distrail! nice find.
Lieutenant MacReady was quite the badass back then, there's more detailed accounts of his flights here:
https://media.defense.gov/2011/Apr/25/2001330216/-1/-1/0/110425-D-LN615-004.pdf
With some early chemtrailing (Actually cropdusting, also in 1921):
His own account of the 1921 flight (attached) is fascinating, although he does not mention the contrails — presumably not having seen them form behind him (or it might actually have been a later flight)
https://media.defense.gov/2011/Apr/25/2001330216/-1/-1/0/110425-D-LN615-004.pdf
With some early chemtrailing (Actually cropdusting, also in 1921):
His own account of the 1921 flight (attached) is fascinating, although he does not mention the contrails — presumably not having seen them form behind him (or it might actually have been a later flight)
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I occurred to me that sunset contrails are quite pretty, so might historically have been mentioned in the past, so I did a search, and found this from 1956
https://books.google.com/books?id=q...cAhWJilQKHZQKBX8Q6AEIPjAF#v=onepage&q&f=false
Not specifically persistent though.
https://books.google.com/books?id=q...cAhWJilQKHZQKBX8Q6AEIPjAF#v=onepage&q&f=false
Not specifically persistent though.
Graham2001
Active Member
Not a book, but a 1920 film (With modern royalty free music.) about clouds by the US Department of Agriculture, again it shows that clouds back then are no different from clouds now.
Not a cloud book, but I'm reading the diaries of the politician Alan Clark (1928-1999), and this entry from summer 1983 caught my eye:
Google Books link
Clearly describing persistent spreading contrails over southern England.
Google Books link
Clearly describing persistent spreading contrails over southern England.
Scaramanga
Active Member
Chemtrail advocates often say that they've only started seeing parallel lines of cirrus type clouds in the sky in recent years. Well...one of the things I inherited from a relative who was in the RAF Royal Observer Corps was a copy of the 1938 Meteorological Glossary. And here is what it says on cirrus clouds...
The problem is that we're seeing persistent contrails in the dead heat of summer which is nowhere near -40 C.
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cloudspotter
Senior Member.
The problem with that claim is that the aircraft aren't on the ground. The temperature at around 30,000 feet will be very different
Miss VocalCord
Senior Member.
This was the temperature around 33.000ft in early July 2019
https://earth.nullschool.net/#2019/...raphic=-110.63,35.27,1368/loc=-117.260,34.606
And as you can see, enough planes flying around at that height to create contrails:
https://www.flightradar24.com/34.72,-118.9/6
Attachments
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Many passenger airliners have information displays on the TV screens on board which show the current altitude, speed, location and often the external air temperature. Have a look next time you are on a plane. No matter how hot it is on the ground, chances are it will be somewhere in the -40C range or below when you are at cruising altitude.
Alexandria Nick
Active Member
Almost counter-intuitively, higher surface temperatures actually increase icing conditions at altitude. Specifically, small ice crystals affecting engines and sensors are more likely to form in relation to thunderstorm systems and tropical storms, two places with surface temperatures higher than normal. Most of the research right now is going into figuring out what size the ice crystals are and how, exactly, they're formed because they currently can't be tracked on radar.
https://journals.ametsoc.org/doi/full/10.1175/JTECH-D-15-0246.1
https://journals.ametsoc.org/doi/full/10.1175/JTECH-D-15-0246.1
What that's saying is that in the course of that particular study, that the areas around a tropical storm were producing more ice at altitude than regular thunderstorms, despite the temperature at altitude being the same. The higher water and surface temperatures under a tropical storm are lofting more moisture up to the level where ice can form, because there's a higher rate of evaporation.Flights 12 and 13 were the only flights to be performed in the same long-lasting quasi-stationary system, a tropical storm, and for these two flights, the concentrations of large ice particles were found to be higher than in all other clouds sampled at the same temperature level. MMDs mostly exceed 500 μm and even reached 2 mm. Moreover, in these flights MMD tended to increase with increasing TWC, the opposite trend found for the classical shorter-lived oceanic MCS.
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