The greatest show off Earth

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Imagine if a movie theatre were to offer free lifetime passes to anyone who asked. “Preposterous!” you exclaim. “They’d be out of business quicker than you could say ‘Orson Welles’!”

Yet, in a sense, that is what the skies offer us every day, throughout our lives: a non-stop film festival complete with drama, adven­ture, romance and even humour. Playing on the biggest screen of all, the show starts before sunrise, and the final credits don’t roll until well after dusk.

Sometimes the players are dark, menacing Marlon Brando types; at other times they are curly-coiffed and vivacious—little Shirley Temples lollipopping across the blue. Occasionally, all the characters leave the set—but not for long.

Despite appearances, each day’s billing is unique, and if you suspect you’re watching a rerun, perhaps you haven’t got to know the actors well enough. Help is at hand. In this issue, we introduce some of the key players in the article starting on page 78 and in the poster. We hope that by sorting out the cumulonimbuses from the cirrostratuses we will provide a knowledge base and an incen­tive for budding cloud-spotters to keep more than just a weather eye on what’s happen­ing aloft. Perhaps you’ll be inspired to keep a cloud journal, and learn to predict what different cloud types mean in your locality.

We titled the article “The Glory of Clouds” because it seemed the more we delved into cloud science, the more extraordinary and captivating clouds became (and the more ignorant we realised we were). For a long while, I had been puzzled by a phenomenon which is sometimes encountered when flying above cloud. Suppose you are on the left-hand side of an aircraft, and the sun is low and shining from the right. If the angles are just right, you can see a rainbow-coloured halo on the surface of the cloud to your left, travelling at the same speed as you are.

This phenomenon is actually called a “glory.” It is caused by light waves being refracted and reflected from the internal surfaces of water droplets in the cloud, then setting up an interference pattern which appears as a disc of coloured light. On occasions, the shadow of the aircraft can be seen in the centre.

A similar effect is sometimes seen by mountain climbers when there is low cloud around the tops, or fog in the valleys. If the shadow cast by the observer on the glory is enlarged, the result is impressively surreal and is called a “Brockenspectre.”

During the course of researching the cloud article, associate editor Warren Judd recalled his somewhat unusual induction into the school of cloud watchers:

“In the summer of 1966, I scored one of the most finely judged passes of the year in the University Entrance Scholarship exam-50.1 per cent average over five subjects.

“My teachers were unimpressed. I blamed the clouds.

“November that year was so pleasant that I had decided to study outside. Stretched out on a mat in the back yard, the terror of the exam room weeks away, Latin grammar soon lost its power and my wandering eyes discovered the sky pageant overhead. Clouds had always been there, of course, but I’d never noticed their antics before. Now puffy Santa Claus eyebrows arching slowly out of the west would elongate, soon to develop balding, wispy patches, and in just a few minutes would break into three or four waning fragments. As often as not, they would dematerialise entirely, thinned to nothingness by the gleam of the sun.

“Perhaps it was a celestial metaphor of my declining grasp of a year’s facts; to me it was unexpected, fascinating stuff. As the weeks passed and the days of reckoning grew closer, so my appreciation of the clouds grew sweeter. Nearly three decades later, Robespierre and the Girondists, Laurence Sterne and Tristram Shandy are almost forgotten names in an empty memoryscape. Yet my memory of those clouds remains a delight, and I reckon that I gained more than the marks I lost.

“Never since have I spent so long gazing aloft, but I always look for those moments of surpassing beauty when God splashes unusual light and texture across his canvas the clouds, and think how boring the sky could be without them.”

Next year marks the centenary of the first International Cloud Year, during which participants from around the globe pooled their observations and advanced the science of meteorology. Although today’s meteorologists rely far more on satellite and radar technology, clouds have not yet been eclipsed (so to speak); the observation and naming of cloud patterns remains an important part of weather forecasting.

Perhaps we should declare 1996 the second international year of the cloud, and devote ourselves to a fresh viewing of the skies.

Any starters? Admission’s free, you know.

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