MetService meteorologist Mmathapelo Makgabutlane had defined it was cloud iridescence however upon additional evaluation, clarified it was truly one other uncommon phenomenon.
“The tell-tale is that if it will get sufficiently big, it virtually has a little bit of a curve to it,” Makgabutlane mentioned.
The 2 meterological phenomenons are simply mistaken for each other, however the course of was barely completely different, Makgabutlane mentioned.
A circumhorizontal arc or a circumzenithal arc each occurred with ice crystals which made up excessive clouds that had been within the skies above Wellington on Tuesday.
The scattered clouds had been cirrus clouds which had been overlaying many of the South Island together with a chilly entrance and a few had drifted over to Wellington with a south-easterly wind, Makgabutlane mentioned.
A circumhorizontal arc appeared when the solar was excessive within the sky and subsequently fashioned low within the sky (like yesterday), whereas a circumzenithal arc fashioned excessive within the sky when the solar was low within the sky.
Cloud iridescence alternatively, might happen with each rain or ice droplets, Makgabutlane mentioned.
As for the distinction in course of, each phenomenons concerned the bending of sunshine.
Cloud iridescence concerned a course of referred to as defraction the place mild bent within the gaps round ice or rain particles, whereas circumhorizontal and circumzenithal arcs concerned a course of referred to as refraction the place mild bends passing via one medium to a different; from the air to contained in the ice crystal and out once more.
“Ice crystals kind in several orientations excessive within the sky, and when daylight refracts, or bends, via the highest, horizontal face of the crystal, and leaves via a vertical aspect, it causes the sunshine to separate into the completely different colors we’re in a position to see.”
So, how do you inform the distinction between the 2 if you’re fortunate sufficient to identify them once more?
Firstly, in each circumstances, seeing them would rely upon the composition of the cloud, angle of solar and the time of day, Makgabutlane mentioned.
“We’re fairly fortunate every part lined up fairly properly.”
One of many methods to inform the distinction, was how the colors appeared.
The method that fashioned iridescence might bend the sunshine in ways in which made them seem scattered, whereas within the arcs, the colors had been extra uniform – much like what most individuals are conversant in in a rainbow.
“We might see that the colors had been extra uniform,” Makgabutlane mentioned.
The confusion between the 2 was potential when the arc was starting to kind, however “as soon as it is sufficiently big, you possibly can type of see the form,” she mentioned, additionally therefore the names of the arcs.
“These are most likely the issues to look out for.”
Whereas the arcs additionally trusted having the precise form of crystals, a circumhorizontal arc like yesterday’s was additionally comparatively short-lived.
“We had been fairly fortunate to catch it when it occurred.”