Peter van Vliet Astrophotography

Green flash

"Cloud-top" flash

Top: the original image. Bottom: detail of the original image.

Recently, I contacted Mr Green flash: Andrew Young. He said this about my image:

"The "cloud-top" flash is a kind I don't understand well yet.  They are
perhaps the 3rd commonest class.  I would say that about 3/4 of all
flashes *seen* are inferior-mirage flashes, and most of the rest are
mock-mirage flashes.  [However, the ones *photographed* are about 2/3
mock-mirage and 1/3 inferior-mirage flashes, because it is easier to catch
the mock mirages, and they are a bit brighter and easier to get correctly
exposed on film.]  Cloud-top flashes constitute something like 3% or 4% of
all flashes seen, I think."

And more about my photo:

"Very interesting!  This is a nice example of a "cloud-top" flash, which is
a type I don't fully understand.  However, your image shows some useful

First, the extreme flattening of the flash shows that it is produced at a
thermal inversion -- which I had already suspected, as these are commonly
seen at the upper edge of marine stratus, which is capped by an inversion.

Second, the very clearly visible diagonal fine structure slanting from
lower left to upper right in the flash shows that there are small-scale
waves on the inversion.  I have seen this kind of structure many times in
other flashes associated with inversions."

If you want to know more about this phenomenon, visit Andrew's page:

Go to my website

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