| Title | Radar Indicates Stronger Hurricanes Trap, Transport More Birds | |
| Date | Friday October 08 2021, @09:12PM | |
| Author | chromas | |
| Topic | ||
| from the birds'-eye-and-other-puns dept. | ||
Reports of birds being trapped in the center of hurricanes date back to at least the 19th century, when crews observed the phenomenon from the bows of ships and saw their vessels become mobile ports for exhausted birds.
"It's been really fun reading some of these older observations from the 1800s about taking a ship through a hurricane eye and watching birds landing on it," said Van Den Broeke, associate professor of Earth and atmospheric sciences. "So we've known for a long time that this happens.
"But it's really only since (the advent of) radar observations that we have gotten any sense of how many of these systems actually do transport birds and insects."
The technology that allowed meteorologists to really begin differentiating weather from organisms -- dual-polarimetric radar, which added a second, vertical dimension to previously one-dimensional observations -- became widely available only in the past 10 years. Which means that much still remains unclear about when, how often and under what conditions a hurricane turns a free bird into a whirlybird.
[...] Though the intensity of a hurricane may hold the greatest sway, Van Den Broeke came across evidence that timing and geography matter, too. The largest bioscatter signatures appeared in hurricanes that occurred between July and October, when many bird species are migrating southward to the tropics, suggesting that native seabirds are not alone in getting swept up. Bioscatter was also larger and denser, on average, in hurricanes that struck the Gulf Coast and Florida, which boast a larger concentration and diversity of birds than other areas struck by the recorded hurricanes.
[...] He's now analyzing inversion data collected by parachuted instruments, called dropsondes, that are released within hurricanes from aircraft flown by the U.S. Air Force and the National Oceanic and Atmospheric Administration.
"I'm comparing the observations of inversion height to the bioscatter signatures," said Van Den Broeke, whose work is supported by the National Science Foundation. "Does it match up? Do birds fly above that? Below it? And can we say something, then, about intensity changes in tropical cyclones, and relate that to how the bioscatter signature behaved?
"It's possible there's some kind of systematic effect there."
If so, bioscatter altitude might eventually become a radar-based proxy for hurricane traits that can currently be measured only via dropsonde.
Journal Reference:
Matthew S. Van Den Broeke. ZSL Publications [open], Remote Sensing in Ecology and Conservation (DOI: 10.1002/rse2.225)
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