1. JRBids

    JRBids Senior Member

    What are these blue splotches? I did do a search, can't find.


    [Mod Edit] It's migrating birds, see discussion below
    Last edited by a moderator: May 12, 2016
  2. Mick West

    Mick West Administrator Staff Member

    Looks like it's an unprocessed dataset showing artifacts near each stations from bugs, birds, and bats.



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  3. deirdre

    deirdre Moderator Staff Member

    image search pulls up alot of similar maps and they all say "birds"
    birds1. birds2.PNG
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  4. Spectrar Ghost

    Spectrar Ghost Senior Member

    Last edited by a moderator: May 12, 2016
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  5. Chew

    Chew Senior Member

    Before radar they used the moon to estimate the populations of birds that migrated at night:

    Last edited by a moderator: May 12, 2016
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  6. Mick West

    Mick West Administrator Staff Member

    Some keywords for searches: Aerofauna, Bioscatter, biological scatterers.
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  7. JRBids

    JRBids Senior Member

    Thanks. Doh! I should have known that. Sorry Mick I saw you'd asked where I got it from, had a bit of food poisoning and haven't been online the last couple of days. ;(
  8. CeruleanBlu

    CeruleanBlu Member

    Another example of this tonight:


    National Weather Service Greenville-Spartanburg, SC reports the following:

    Source: https://twitter.com/NWSGSP/status/851984022972624897
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  9. chemfiend

    chemfiend New Member

    those blooms happen at night, every night,unless it is workin a storm,not birds or bats cause it happens at night in the winter too!
  10. chemfiend

    chemfiend New Member

    only geese and cranes migrate at night and it isnt in a circular blob, the bloom starts at the radome and goes outward in a circle
  11. Spectrar Ghost

    Spectrar Ghost Senior Member

    The lowest elevation on a WSR-88D is 0.5 deg. It starts at the radar and works outward because the beam is lowest to the ground nearest the radar. You're not seeing the returns spread outward, you're seeing them spread upward.
  12. scombrid

    scombrid Senior Member

  13. scombrid

    scombrid Senior Member

    This is a really cool year-long timelapse of radar and infrared satellite imagery. You can see the pattern of nocturnal radar "blooms" in the spring and fall in relation to weather systems. If you skip to the 8 minute mark and watch from 8:00 to 9:00 you can really see the fall migration pouring down to the southeast and gulf coasts. The birds come down behind the cold fronts and then really pool up along the coast then the fronts stall out over Florida. We get to see a lot of cool birds here for a couple of days until the next bigger front clears the state and the birds decide to make the trans-gulf flight to South America.

    Source: https://www.youtube.com/watch?v=D13pthfl0bM&t=15s
    Last edited: Apr 12, 2017
  14. scombrid

    scombrid Senior Member

    Someone asked in the comments about the "stationary blobs" that formed almost every day from April to June. I paste my reply here:

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  15. chemfiend

    chemfiend New Member

    so these radar blooms the blossomed around nine pm like every night , and that are still blooming at 2am, are migrating birds and bats? highly unlikely considering nothing is migrating and there isnt swarms of bats all night long.
  16. Trailblazer

    Trailblazer Moderator Staff Member

    Read the above posts. Yes, millions of birds migrate at night each spring and autumn.

    No, again read the links above. Many, in fact most, species of land birds migrate at night.


    That same article states that as many as 5 billion birds migrate in North America each fall (autumn), so presumably a similar number migrate in the other direction each spring.
    Last edited: Apr 14, 2017
  17. scombrid

    scombrid Senior Member

    I'll reiterate:

    Type bird migration radar into Google Scholar to learn more than you may care to know about tracking bird migration with radar.


    Some of the articles go back quite a few decades. As soon as radars were deployed to detect other stuff in the air there were biologists that had the idea that radars could provide a glimpse into the unseen world of nocturnal bird migrations.
  18. chemfiend

    chemfiend New Member

    ionization of the atmosphere for geoengineering maybe, migrating birds it is not!
  19. Svartbjørn

    Svartbjørn Senior Member

    State your source.

    State your source.

    State your source.
  20. Whitebeard

    Whitebeard Senior Member

    Many small birds migrate at night, fewer predators around to hunt them. OK there are owls, but owls are on the whole hunters of ground prey not aerial targets

    And don't forget nocturnal insectivorous species such as the Nightjars, which prey on night flying insects such as moths
  21. solrey

    solrey Senior Member

  22. Trailblazer

    Trailblazer Moderator Staff Member

    These radars show what is happening at relatively low altitude, where rain is falling (and birds are flying). If the atmosphere was being "ionised" then it would be conductive, and you'd see obviously effects such as overhead power lines arcing to ground. Have you got any evidence for this? And are you suggesting that the numerous scientists who track migrating birds by radar are mistaken?
  23. scombrid

    scombrid Senior Member

    Weather radar just an antenna scanning the sky for reflections of its own broadcast radio waves and then a computer displaying graphical representations of the returned signal.

    If there is "ionization" in the atmosphere you won't see it on a weather surveillance radar. The weather radar is showing you things that are big enough and solid enough to reflect the radio waves back. Doppler shift of the signal tells you the velocity of the target relative to the radar station. Intensity of the signal is used to estimate the number of targets after other mathematical gyrations estimate the average size of the targets.

    But the simple fact is that the weather radar only "sees" objects that are reflective of the wavelength that it broadcasts in the first place.
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  24. Ross Marsden

    Ross Marsden Senior Member

    They could also be insects; moths, for instance.
  25. chemfiend

    chemfiend New Member

    so the return to the radar if it were geese would show extreme hail, bats would be golf ball sized hail, so from the radome in valley nebraska west there are no bugs birds or bats, but east of that there is so many that i personally standing near the radome cannot see or hear them?
  26. Spectrar Ghost

    Spectrar Ghost Senior Member

    Size is not the only factor in determining radar returns, as the B-2 Spirit shows.

    Hail in particular produces a very strong return, due to the fact its liquid coating makes it look to the radar like a very large raindrop. Return increases proportional to droplet diameter to the fourth power, so hail shows as very high dBzs (typically >60dBz).

    Birds and bats do not have a large reflective surface orthogonal to the radar beam, and thus produce much less intense returns.

    I'm not sure how to parse this - perhaps you could clarify?
  27. scombrid

    scombrid Senior Member

    Add to that, how close together the targets are to one another affects the intensity of the return. Birds migrating at night are really spread out compared to rain drops or hail stones.

    Tree swallows sometimes aggregate in the millions in the willows in the swamp just west of the radar here in Melbourne, Florida. They make diurnal (daily) foraging trips while staying in the area. They fly up and out from their roost early in the morning. There will be a very bright return at the roost as the all lift off and then the return spreads out and dissipates as they disperse. Look up "Purple Martin Roost Ring" radar images for an example. When they return in the evening they are generally flying under the radar and aren't detected. But, the colony in Melbourne is so close to the radar that when they mass up in the evening over the roost the radar picks them up and it produces a bright red spot for a couple of frames.

    You can see a nightly version of the same thing from Mexican Free Tailed bats in central Texas during certain times of year.
  28. scombrid

    scombrid Senior Member

    They are high and far away and it is night. That is why ornithologists have locked onto weather surveillance radar part of their toolkit for tracking nocturnal migration.

    I live in Central Florida. I had an American Redstart flitting around my back garden among the butterflies for a few days while there was a cold front to our north blocking migration for a couple of days. Redstarts like most neotropical migrants breed up north on the continent somewhere and winter in the tropics. We only get to see them in Central Florida on stopovers. Well, the high pressure shifted offshore and the southerly flow on the back side opened the door for another round of northerly flying. My little playful friend moved on to his breeding territory some place many miles north.

    The Jacksonville radar lit up last night with almost the entire scan showing targets moving in a northerly direction. I've got an animated gif but I can't get it to load.
    Last edited: May 16, 2017
  29. scombrid

    scombrid Senior Member

  30. scombrid

    scombrid Senior Member

    While not the "blue splotch" nocturnal signature of spring and fall mass migration, here is a study of Tree Swallows as I described in the previous post.