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meteoptic-l [ät] ursa.fi
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Hi,
> - when seeing such a bow, download and save precipitation radar images
of
> the local weather office. Maybe it can be figured out in which
direction
> the bow was and in what range of distances, and correlate this with the
> precipitation intensities.
There are some problems with this. Weather radar scans are made
typically once in 5 to 15 minutes (rainfall can change a lot in a
minute, especially when convective rain is considered), the resolution
is usually rather coarse, hundreds of meters in radial direction and
even more in tangential (depending on how far the precipitation is
from a radar), the radar beam is near the ground only close to the
radar and the rain above the rainbow is not necessarily the or even
similar to the rain within the rainbow, etc. I would not bet my money
for this being useful, although it doesn't mean it couldn't be.
I'd say the most important thing is to take photographs and make notes
on the conditions. Things like the duration of the twinned rainbow,
if there were changes in the bow (and how much, how fast), etc.
We might actually want to compile a list of useful information.
One last thing. If this phenomenon truly is a product of nonspherical
raindops, there is another such bow showing up in the sims that might
be real as well. Sims indicate that sligtly flattened drops would
produce a rainbow-like arc about 90 degs _below_ the sun (i.e.,
against the ground), when solar elevation angle is some 40-50 degs.
Exact location and elevation angles depend on the shape of drops.
The bow shouldn't be strongly polarized and might be colorless.
So, if you happen to see rainfall in the direction of sun and
happen to be in a plane, tower, or a mountain, take a look. First
observer might get to name it. ;-)
Timo
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