I have always been a keen observer of clouds, even more so since moving
to Tasmania. I don’t know whether it’s simply the fact we are an island, but
the variety of clouds I observe on any day makes me often wonder what on earth
is going on up there. With competing air currents from every which way, you can
often spot several different cloud formations in what appears close proximity,
though they are probably all zotting this way and that at different altitudes.
I was taken aback though when I first spotted these nacreous clouds on a
winter’s day two years ago. They intrigued me as I’d never seen anything quite
like it, a shimmering opalescent quality like the mother-of-pearl sheen inside
an abalone or oyster shell. Nacreous clouds form in the stratosphere (15000 –
25000m) which is normally very dry, but occasionally during winter, moisture
can be driven much higher into the atmosphere where at extremely low
temperatures ice crystals form in the clouds and the phenomenon of cloud iridescence
occurs as light is refracted by the crystals.
Unfortunately, their beauty has another side, a destructive feature
borne out of our own ignorance, and one we’ll have to live with for decades to
come. The ice crystals contribute to the breakdown of the ozone layer by
reacting with other gases in the atmosphere, namely those connected with the
use of products containing CFCs over a prolonged period of time.
It’s hard to believe something as small and insignificant as a single
cloud way, way up high could also be detrimental to the planet. Here’s hoping
we come to our senses and work to right our wrongs as the future unfolds.
Strange nacreous clouds
iridescent, beautiful
darkly destructive
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