1. Kaylene

    Kaylene New Member

    Recently I had my first trip to the West Coast of America and was shocked by all the contrails in the sky. Here in Western Australian we are lucky to see one every now and then. I understand that there are a lot more planes in the US but after reading up to find out what they actually were my question is, do we have a drier atmosphere than America? I'm not scientifically inclined, just a curious person in general and was hoping someone could answer me in laments terms
     
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  2. Spectrar Ghost

    Spectrar Ghost Senior Member

    [​IMG]
    http://aerosociety.com/News/Insight-Blog/1644/ATM-a-vision-of-the-future#gallery[m]/0/

    Looks like it's primarily matter of relative traffic.

    Western Australia is under the subtropical High formed by the convergence of the southern Hadley and Ferrel cells -
    [​IMG]
    - (thus the great western desert), which results in relatively dry air at altitude as well, but I'd imagine air traffic is the primary driver of the difference.
     
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  3. Trailspotter

    Trailspotter Senior Member

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  4. Trailblazer

    Trailblazer Moderator Staff Member

    And even what little air traffic there is in Western Australia is mostly traffic to and from Perth. So in and around Perth you won't see contrails overhead from that traffic, because it won't be high enough to be leaving contrails. (Sometimes you can see them out over the ocean where they are high enough, maybe 60 or 70 miles away from the airport either inbound or outbound.)

    Very few flights will be passing over the population centres of Western Australia at cruising altitude.
     
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  5. Mick West

    Mick West Administrator Staff Member

    Yes, this is the key point. In the places where people live in Australia (and even more so in New Zealand) the vast majority of flights nearby are taking off or landing at a local airport. This is very different to the US where all large population centers (and most of the rest of the country) is overflown by flights going between distance cities, and hence at contrail altitude.

    This thread has several visualizations of this.
    https://www.metabunk.org/visualizing-flight-paths-above-30-000-feet.t812/

    Here are the tracks of planes, only when they area above 30,000 feet:
    [​IMG]

    And the same for australia:
    [​IMG]

    In both cases you can see the tracks ending as they go in/out of a city (most noticeable on the West Coast of the US). But around Perth (bottom left of Australia) theres almost no overflights.

    And here's a close-up of NZ

    [​IMG]
     
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