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CINDY DAY: Circles in the sky

Ken Simmons spotted this rare circumscribed halo high in the sky over Kelligrews - Conception Bay South - NL on Wednesday.
Ken Simmons spotted this rare circumscribed halo high in the sky over Kelligrews - Conception Bay South - NL on Wednesday. - Ken Simmons

I’ve always loved to look up at the clouds.

Back on the farm, after a long, hard day, mom would lie down for a rest on the cool grass and invite my sister and me to join her.  We would stare up at the clouds and look for faces or animals in the always-changing clouds.  I still find clouds fascinating. 

I love the fact that some people still look up!  On Wednesday, Ken Simmons noticed intriguing rings around the sun in Conception Bay South, N.L.  It was a halo, but not a typical halo!

On Wednesday, veils of high-level cirrostratus cloud associated with a warm front, were reaching across the island.  Cirrostratus clouds often serve up lovely solar haloes, but this one was different and not very common at all: it was a circumscribed halo.

A circumscribed halo is a type of halo in the form of an oval ring that circumscribes the more circular, or regular 22° halo centred on the sun.  

The shape of the circumscribed halo depends on the distance of the sun above the horizon.  When the sun is low in the sky, the sides form two distinct, downward-drooping “lobes” outside of the 22° halo.  As the sun rises higher in the sky, the drooping diminishes and you get a more regular oval shape.  Finally, when the sun is high in the sky, the shape of the circumscribed halo approaches a circle, and it can completely cover the halo.

Like most halos, it’s slightly reddish on the inner edge, facing the sun, and bluish on the outer edge.  The circumscribed halo also occurs around the moon.

Another good reason to look up!  Thanks Ken!

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