1. Rory

    Rory Senior Member

  2. Spectrar Ghost

    Spectrar Ghost Senior Member

    Based on context I'd presume it's a reduction in surface temperature of 0.159C.
     
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  3. Graham2001

    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.
     
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  4. SR1419

    SR1419 Senior Member

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  5. mikret

    mikret New Member


    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.
     
  6. Mick West

    Mick West Administrator Staff Member

    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
     
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  7. L. Baker

    L. Baker New Member

    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.
     
    Last edited by a moderator: Nov 24, 2017