Category Archives: meteorology

Iron Noder

This November I posted 30 finished pieces of writing on Everything2, on whatever I felt like writing about at the time. By doing so I completed the Iron Noder Challenge, which has been running every November since 2008. This was the first time I took part in earnest – making the effort to write and re-write for an hour or two almost every day, in order to average at least one post a day that I could be happy with. Continue reading Iron Noder

The Rain in Carballo

Carballo at night

I’ve been a little slow to start going through my photos from this Summer’s two-month trip around the Iberian peninsula.

I stayed for about two weeks in the town of Carballo, which is 35km from A Coruña, 45km from Santiago de Compostela and 10km from the nearest beach. It’s a small, quiet town full of empty buildings, half-finished or abandoned, slapped together with an obvious disregard for any kind of building code. Most of the bars are mostly empty most of the time, and presumably they couldn’t stay open at all if they had to pay the kind of rent you have to pay for premises in places where people want to live. There is life and music if you know where to look, though, and it’s an easy enough journey to the beautiful beaches.

A clear stream runs through Carballo, past the bus station. close to where I was staying, with fish and bats and dragonflies. It leads quickly out of the bricks and concrete, into the woods, like an artery. The air is fresh, and the hazelnuts you can pluck from the trees in late summer are like a taste of heaven.

The last night I was there, I was woken by a mighty rainstorm battering against the thin roof of my attic flat. It’s the rain, above all, that makes Galicia so gorgeous, once you get outside of its depressed not-quite-seaside towns – the rain that feeds its lush forests and sustains its wide green fields. The countryside throughout northern Iberia is stunning; you might miss the sunshine, but it’s worth getting wet for.

The Cloudspotter’s Guide

The Cloud Appreciation Society was founded by Gavin Pretor-Pinney in 2004, to ‘fight blue-sky thinking’, with the motto: ‘Look up, marvel at the ephemeral beauty, and live life with your head in the clouds‘: Sound advice if I ever heard it. The Cloudspotter’s Guide is its first official publication, and the author’s first book.

Pretor-Pinney also designed the Guide, typeset it and put together the diagrams, and in every case he has done a beautiful job. This volume is gorgeously produced, with a delightful, atmospheric woodcut opening each chapter, plentiful photography throughout (mainly contributed by members of the Society) and the old iconic cloud symbol from the BBC’s weather forecasts serving as a vignette between each section. All in all, the design gives the book a dreamy, flighty air, in keeping with both the subject matter and the style of the prose.

The writing is fluid and un-self-consciously eloquent, rambling without ever getting tedious, educational without ever getting lecturey. The author skips amiably from topic to topic, interweaving personal and historical anecdotes, scientific observations and poetic ruminations on the beauty and vitality of the skies.

Each of the major classes of cloud has a chapter dedicated to it, always going into some depth about what characterises the clouds in question and talking a little about the meteorology of it, but often spending more time talking about other things – clouds in history and art, say, or various phenomena that come along with the clouds themselves (most of the Cirrostratus chapter is devoted to discussing ice haloes, for example; much of Nimbostratus is about rain from all sorts of different clouds).

The beginning of each of these chapters features a summary table for the clouds that are its nominal subject, giving a few illustrative photos, telling you where they form, in what species and varieties they appear, how to distinguish them from any superficially similar clouds, and so on.

The scientific details are substantial enough to satisfy the amateur meteorologist in me, but never so technical as to bog down the flow of the writing; where the author has had to simplify to make it comprehensible to the general reader, he is not afraid to say so, and the insatiably curious can always follow his pointers to more in-depth work.

Mammatus cloudsAfter the ten chapters for the main cloud groups, the last section of the book (‘not forgetting…‘) goes onto things which couldn’t quite be fitted in elsewhere. First, there is a chapter on The Other Clouds – accessory clouds such as the pileus (‘like a cloud haircut’) and pannus (‘dark shreds of condensation, which form like ghostly apparitions in the saturated air of rainfall’) which only appear alongside other clouds; supplementary features such as the incus (anvil) that often extends from the top of a Cumulonimbus cloud, or the breast-like mamma clouds that occasionally blob from the bottom of that; and the high, high clouds that form way above more common clouds, up in the mesosphere or the stratosphere – nacreous and noctilucent clouds respectively.

Chapter Twelve’s subject is contrails, the trails of condensation that form behind high-altitude aeroplanes.These streaks may provide an interesting glimpse into the process of cloud development, but they are also strongly implicated in climate change; it is largely thanks to them that the contribution of aeroplanes to the greenhouse effect is almost three times as large as it would be if CO2 was the only thing we needed to worry about. Much of the chapter is spent exploring the threat of global warming as it relates to aeroplane exhaust, with a substantial portion also given over to the history and science of cloud seeding – a technology which can be surprisingly effective in inducing rainfall (albeit only when the conditions are right), and which gets discussed oddly rarely considering the power of it.

In the final chapter, the author goes into journalist mode to recount in detail his mission to visit the Morning Glory, a spectacular and near-unique cloud formation in northern Australia, where rolls of cloud can be seen stretching from horizon to horizon as they make their way over the outback. Glider pilots come from all over the world to surf on its extraordinary, visibly roiling updrafts, and witness one of the world’s most awesome clouds. Despite the stylistic departure, the story provides a surprisingly elegant close to the book, as the author soars alongside a few of this planet’s most devoted cloud-lovers.


AweI recently finished reading The Cloudspotter’s Guide (see review), and have concluded that it is one of my all-time favourite books. I have made skywatching a hobby for as long as I can remember, but the book has raised my awareness of the skies above us to new heights. As it happens, this has coincided with some absolutely pheomenal skywatching weather in Edinburgh, warm seas and sunshine feeding vast Cumulus clouds, weather fronts dropping stunning Cirrus squirls from the heavens, fascinating layers on layers of different clouds.

I’ll return to the book later; for now I just wanted to share the results of just two day’s skywatching…

The first of those days found me sitting in Holyrood Park one fine, sunny-cloudy afternoon after work, with my camera and a copy of The Cloudspotter’s Guide, with nothing to do but read about, watch and record the sky. The weather was as good as perfect for it – strange ice clouds high above, brooding storm clouds just far enough away not to alarm, and enough sunshine to keep us warm and illuminate the early-autumnal haze with lovely crepuscular rays.

Cirrocumulus lacunosus undulatusWith the help of the Guide I was able to identify this unusual net-like formation with some confidence as a Cirrocumulus lacunosus undulatus – that is, a collection of high, icy cloudlets forming a layer punctuated by holes – lacunas, if you like. Granted, that doesn’t tell us much of any real use, but still, it’s always nice to be able to put a name to something that’s been puzzling you.

Puny HumansThe banks of Cumulus congestus dwarfed the Salisbury Crags, which in turn dwarfed the people climbing them. I knew that it would rain on us sooner or later, but I had time to capture a series of pictures to turn into a highly amateur time-lapse film, so that I could watch those beautiful convection cells in action later. There’s a small version of this here, but if your computer can take it I recommend the full 2-megabyte version. I could have saved myself a lot of work later if I’d had a tripod with me – and a timer would help – but I didn’t have anything fancy to hand, so I just balanced the camera on my knees and took a picture every few seconds for a couple of minutes – compressed here into a couple of seconds.

A few weeks later the skies around Edinburgh were dominated by vast, looming, ever-growing Cumulus congestus and Cumulonimbus: puffy, dramatic and often deceptively solid-looking rain clouds, pouring down their loads even as they burgeon with freshly condensed droplets, up-wellings of warm, moist air racing to refresh them before they rain themselves out. I was staggered to end up avoiding the rains entirely, though it can’t have been more than a mile or two away at any point in the afternoon.

That day’s convection clouds came accompanied by a smattering of Cirrus clouds streaming out of a subtle Cirrostratus, showing that the air was moist right up to the highest reaches of the troposphere – to the tropopause, where the weather stops. Their ice crystals refracted the sunlight in a stunning range of displays; I have been watching out for such things for years, but had never seen such a range of ice halo phenomena in one day.

There were striking sun dogs (also known as parhelia, or mock suns) – the most obvious of the halo phenomena, these appear more than once a week in northern Europe, but most people still fail to notice them. They are created by horizontally-aligned plate-like ice crystals; the sunlight passes through one side of these transparent hexagons and out of another, making a bright, coloured patch of sky 22° or so away from the sun – about the distance from thumb to little figure of an outstretched hand at arm’s length. The colours are not always obvious, but when they are you can see that the sun dog is reddish towards the sun, and bluish on the other side – sometimes with a long, not entirely un-doglike tail.

The exact same kind of ice crystals produce the circumzenith arc, a ‘sky smile’ in vivid rainbow colours, going part-way around the top of the sky, above the sun. As on that day, these are therefore likely to be seen at the same time – although they are not seen as often as sun dogs, partly because they only appear when the sun is quite low in the sky. In their case, the bright colours – which at their best can out-do any common-or-garden rainbow – are the result of light entering the top of the ice-plates and leaving through the sides.

Accompanying these, less spectacular but undeniably still pretty, I was unsurprised by the appearance of a 22° halo, the most common halo effect produced by Cirrostratus; these are made by columnar ice crystals, like tiny pencils, which are randomly oriented, and they appear almost one day in three. When these crystals have smooth, flat ends (which they rarely do) they can also produce a 46° halo, much fainter and much larger than their cousin. When the columnar crystals are roughly horizontal, they can also produce a tangent arc, somewhat resembling a giant dove made of pure light. If my judgement is on, I was privileged to see both that afternoon.