fire rainbow = circumhorizon arc

Sunday, March 30, 2008


Daddy sent me a picture of a fire rainbow...and i was like what?
so like every techie baby...i googled it up to find the origins of it...and it's true! (well with photoshop anything and everything is possible)

So I found this photo from TomArgh's blog, looks much nicer than the photo dad sent me

a lil' info of this phenomena called Fire Rainbow aka Circumhorizon Arc

According to the National Weather Service based in US,

A circumhorizon arc is one of the rarest halos one can witness. First. it requires a very high sun angle of approximately 58° or higher. A sun angle this high can only occur at northern latitudes during a small portion of the year centered around the summer solstice. Solar elevations of 58° or higher in Spokane are achieved in a small window beginning in May to the first week in August. Even in this window, the sun angle only exceeds this lofty elevation for a mere hour or so in May and August to around three hours near the summer solstice (June 21st).

But a high sun angle is only part of the recipe. The other ingredient is even more restrictive. This ingredient is a cluster of perfectly aligned (i.e. nearly perpendicular to the sunlight) ice crystals. This alignment allows the light to enter the nearly vertical side of the ice crystal and exit the relatively horizontal bottom of the crystal. The crystals refract the light approximately 46°, resulting in a very pure spectrum of colors and a vivid light display. In the case on June 2nd, we had a layer of cirrus clouds provide the needed ice crystals distribution.

degree must be at 58°
clouds: cirrus type
ice crystals perfectly align

OK back to my's gonna end soon ^^


Anonymous said...

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Fionna Tan said...

hi there =)


nope sorry don't do newsletter at least at this point of time ;)