Discussion in 'Contrails and Chemtrails' started by Mick West, Feb 28, 2014.
What does the 0.159 refer to?
Based on context I'd presume it's a reduction in surface temperature of 0.159C.
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)
The authors introduction recommends the book to meteorologists, artists and anyone who is interested in the sky.
Mick has been using that books for years: http://contrailscience.com/clouds-before-planes-cloud-studies-1905/
Its also on Archive.org
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:
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
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.
This has been posted before, but the version I saw before was the reprint without the last paragraph. This is the original, from:
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.
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:
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)
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
Not specifically persistent though.
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