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James Lowery: "Glory on the Ground" (Nov 13, 18:11):
> This week while I was flying a search and rescue mission with the Civil
> Air Patrol, our plane (a single engine, high-wing Cessna 172) made a
> nice glory on the ground. We were flying at an altitude of 1200 to 1500
> feet above sea level which meant that we were even closer to the ground
> than that most of the time. It was the first time I had been in a plane
> that made a glory on the ground rather on the tops of the clouds.
>
> The interesting thing that I noticed was that the brightness of the
glory
> increased as it passed over *lighter* color terrain. I was expecting it
> to be brighter over darker terrain because my logic was that the bright
> "light" of the glory would show up more against a dark "background."
> This difference in the "brightness" of the glory is probably not noticed
> as much when they are projected on the cloud tops because the clouds are
> more of a uniform color.
>
> Does anyone have an explanation for why the glory was brighter when it
> was projected onto lighter color terrain?
>
Were there any fog at the ground where you observed this phenomenom? The
reason I ask is that glory is result of light scattering in spherical
water drops, such as fog or cloud droplets. If there were no fog and the
phenomenom was observed at the ground, then you probably saw
heiligenshein (hopefully I got it right), which is just a brightening of
the terrain around your shadow. Glory, on the other hand, seem very much
like corona around your shadow, with multiple rainbow colored rings
around your shadow.
If there was a fog layer at the ground where you saw the glory, then
indeed one would expect the glory to be brighter against dark
background, if that is the only difference in observational conditions.
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