THE WORLD OF WATER: A PERSONAL JOURNEY – Part V: When Sunlight Breaks

Like most children, I was a cloud-spotter from the knee-high stage onwards. The cloudscape above the South African veld made an indelible impression on me. Hours on end we children would lie on our backs, the hot sun baking our tanned faces, arms and legs, high above us cumulus clouds suspended in the heavenly blue: Big Ears-ears, Pinocchio-noses, old-man-faces, unicorns and other creatures and landscapes of mythopoeia. Add to that the seemingly endless wisps and stripes of high cirrus clouds, the towering walls of cumulonimbus castles. I imagined an enchanted world amongst the clouds, a world higher and greater than my own down below.

Alas, in contrast to almost all other children, my perception of the world around me has never changed. I still seek for, yearn for, the charmed and enchanting in an otherwise stultifying adult world. So I remain a cloud watcher, peepers pointed skyward, still searching for my fairy queen and yet another glimpse of that other world. Nowadays, however, looking is not enough. For me, as a photographer, clouds remain endlessly fascinating: in constant flux, never static in pattern or process, and especially the incessant wonderful play of light and shadow that arises.

Special excitement is provided by iridescent clouds. When thin cloud layers (particularly cirrostratus, altostratus and altocumulus clouds) are present in the sky, it can happen that sunlight shining through these clouds breaks apart into its rainbow colours. This phenomenon is observed best when the clouds occur in an arc of less than 20° from the sun. Since you are facing the sun, often the light is too bright then to observe the phenomenon or to capture an impressive image on film. It is better to photograph this singular spectacle at sunrise or sunset, especially when the sun is shielded by other clouds so that no light falls directly on the lens.

In general, iridescence appears when surfaces of objects are composed of multiple layers or the surfaces comprise a very thin film, as for example in soap bubbles or when oil is spilt on water. In these instances, the light that impinges on the object is reflected, not off one surface, but off several different tiers. If the incident light originates from a single source (as is the case with sunlight), iridescence occurs strongly since the wavelengths of the reflected light rays coming from different layers can interfere with each other. In this way, some wavelengths are either dampened or enhanced. With interference all the wavelengths reflected off an iridescent object added together no longer appear white (the total sum of all colours in sunlight), but parts of the object now show a colour cast. The resulting spectacle depends on the angle of view, of course.

In clouds specifically, several processes that occur simultaneously cause iridescence. When sunlight passes through a thin cloud layer, some light rays are absorbed; most rays, however, are scattered by the cloud particles, so that the cloud usually appears white. Some light rays pass between the water droplets or ice crystals and are thus diffracted. Other rays pass through the droplets and are then refracted and split into their constituent colours.

Whether sunlight passes through or between water droplets, whether it is diffracted, reflected or refracted, the light rays that finally travel towards the observer can still cause interference phenomena. Since sunlight originates from a single (point) source, all the light rays are still in phase with each other (even after the many changes that have occurred); therefore, two light rays can become superimposed one on the other to give rise to interference. With this, some colours may cancel out; others may become exaggerated, because the different wavelengths of light are affected differently during interference.

The result of this long journey by the light rays through the diaphanous cloud is iridescence. From the point of view of the observer, the angle between the cloud and the sun must be less than 20° for this phenomenon to be visible. In addition, the resulting colour spectacle is dependent on the density of the cloud or cloud layer. If the clouds are very thin and wispy, the colours that appear are washed out and indistinct; on the other hand, if the clouds are too dense, either too much light is absorbed or the rays are scattered too irregularly to result in iridescence. Other factors that modulate the appearance and intensity of iridescence include the size of the cloud's water droplets or ice crystals, the movement of the cloud and the way in which the sunlight impinges on the cloud surface.

Cloud iridescence is not a halo phenomenon, since the colours occur in bands rather than in concentric rings, as is the case with halos. Iridescent clouds also differ from the similar nacreous or polar stratospheric clouds and noctilucent clouds. Although the physical processes involved in all these cases are the same, iridescent clouds can be observed at most latitudes and during daylight hours. The cloud type involved in iridescence always comprises cirrus- or stratus-type clouds in the troposphere (the lowest layer of the atmosphere, starting at the earth's surface and extending to a height of between 7 km at the poles and 17 km at the equator). In contrast, nacreous clouds can only be observed at latitudes larger the 58° from the equator. Also, nacreous clouds are found in the stratosphere (up to 30 km above the earth's surface). In the case of noctilucence, high clouds in the mesosphere (between 50 km and 80 km above the planet surface) may still reflect sunlight after sunset (or before sunrise) during very deep dusk.

So, do I still spend time on my back these days? Of course! The only change that has occurred is that the bones complain when I attempt to stand up after a long sojourn in the magical, mythical realm of clouds.

THE WORLD OF WATER: A PERSONAL JOURNEY – Part IV: Cloudscapes

Ever since childhood the other world that exists, the one high above the grasslands and bushveld of South Africa, has enthralled and fascinated me with its endless watery vistas of cloudscapes. To find a workable photographic composition in this immense realm remains a challenge that I relish. The shapes of the clouds, their flow, their highlights and shadows, and their colours, from the customary white and greys at midday, through all the tints of the rainbow that compose sunlight earlier or later in the day.

Clouds are essentially vast collections of water droplets or ice crystals held up in air. The mass of water that is trapped within a typical cloud can reach several million tons. And yet, the density of the relatively warm air that holds the water droplets in suspension is low enough that air currents below and inside the cloud keep it hanging. Ice crystals are much lighter than water (after all ice floats on water) and can form clouds much higher in the atmosphere under freezing conditions.

Physical conditions within a cloud are never static. Formation of water droplets (around condensation nuclei such as dust or smoke particles) and re-evaporation of water droplets into vapour occur ceaselessly. If, like me, you are often compelled to look skywards, you too will have seen the miraculous-seeming condensation or evaporation of clouds as unseen masses of air pass and mix in the blue sky above you.

The type of cloud that can form at any one time and in any specific air mass depends on only a few local conditions of the atmosphere. The main ingredients for cloud formation are the presence in the air of sufficient water vapour, the turbulence or stability of the air in question, and the presence or absence of convective uplift (that is, the presence of warmer air that will rise in altitude). Essentially, all the different shapes and forms of clouds can be divided into only two categories: layered and convective cloud types. In unstable atmospheric conditions, convection of air predominates, giving rise to vertically-developed clouds, while more tranquil atmospheric conditions give rise to horizontal cloud layers that can extend over great distances.

When attempting to classify cloud types, almost the only other consideration is the height at which clouds form (remembering that the higher the altitude, the less the density of air itself is, and so too its ability to suspend a vast mass of water or ice). High clouds invariably are composed of tiny ice crystals, giving rise to wispy, layered cirrus-type clouds, often spread out in horizontal wind currents over enormous distances. Mid-altitude clouds are composed of water droplets, giving rise to denser, layered clouds or smaller clouds aggregated in cloud fields. At low altitudes in the atmosphere dense, layered stratus-type clouds or scraggly dense fields of low cumulus-type clouds form.

The most dramatic clouds develop in the presence of strong convection currents in the atmosphere. These vertical clouds have fierce internal up-draughts of air and rise above their bases formed at various heights in the atmosphere. These cauliflower- or anvil-shaped cumulus or cumulonimbus clouds, respectively, are often the harbingers of rainstorms or thundershowers.

As sunlight shines on clouds and travels through the mixture of water droplets or ice crystals and air particles, light rays are reflected, scattered, diffracted or absorbed by the bits of the clouds. The colour of the cloud, the wavelengths of light that are reflected from the cloud towards the observer, of course, depends on the colour of the light that is striking the cloud.

During midday hours the tops of clouds and the sides facing the sunlight appear white. The intense white light is reflected and scattered by the water droplets or ice crystals in all directions equally. Even if the light has been diffracted at the surface of cloud particles or inside the water droplets, the reflected light rays from the countless molecules in the cloud recombine to give the appearance of white light. The water droplets comprising a cloud tend to scatter light effectively, so the intensity of solar radiation passing through a cloud diminishes with depth into the cloud. Thus dense clouds show various shades of grey, especially towards their bases. The same greys also appear in areas of a cloud that are shielded from direct sunlight.

Rarely clouds may take on a tinge of colour other than the usual white shade. Most frequently large and very dense clouds will appear blueish-grey due to light scattering within the clouds; the short wavelengths (blues and greens) are more easily scattered, while the longer wavelengths (reds, oranges and yellows) are more easily absorbed. Therefore, blueish clouds indicate strong scattering of light by rain-sized droplets, meaning that a drenching may be imminent. Much less frequently, clouds appear greenish; invariably such clouds are composed of large ice crystals or hail stones that scatter strongly the green wavelengths of light. When clouds appear yellowish, the atmosphere usually contains a large proportion of smoke particles following large-scale fires, natural or man-made.

For a short while, twice a day, clouds are not white and grey or tinged by subtle hues of colour. At dawn and dusk, when the atmosphere and its floating clouds are still shaded from the sun by our planet itself, only the strongly scattered short wavelengths penetrate Earth’s shadow, painting any clouds present in intense hues of violet, indigo and dark blue. As the sun peeks above the horizon in the morning, or before it sets in the evening, clouds become a fiery spectacle of reds, oranges and yellows, as the sun’s rays travel through the air at a shallow angle, with the cooler colours temporarily subtracted from the light.

Whatever the time of day, whatever the atmospheric conditions, clear skies or storms, whatever the cloud types that form, for me the constant flux and flow and the play of light high in the atmosphere above me remain enchanting. Clouds are the manifestation of physical processes happening in the invisible air, giving rise ultimately to the patterns that represent an entire world other than the terrestrial one to which my feet are rooted. Rooted in body to Earth perhaps, but with my imagination skipping among the clouds.

ABOUT THIS IMAGE: ‘In the Hall of the Mountain King’ – The Arm-less Baboon

In December of 2009, my wife and I were visiting the Augrabies Falls National Park in the Northern Cape Province of South Africa. This park is renowned for its waterfall, a place called Aukoerebis (Place of Great Noise) by the original Khoi inhabitants of this very arid, semi-desert and very rocky region of the Nama-Karoo. Here the Gariep River first plummets approximately 60 metres over a narrow lip into a gorge scoured out of a basement of granite rock. The gorge is over 18 kilometres long and averages 240 metres in depth. The sides of the gorge are sheer and polished smooth.

The surrounding countryside is equally spectacular. The vegetation is typically dry, low, open woodland and bushveld. Cutting through this semi-desert environment run ridges of volcanic rock and breath-taking polished granite domes.

On our last day, we visited the falls before sunrise. The mist thrown up by the thundering Gariep was backlit by the first rays of the sun. A half hour later, a small troop of chacma baboons made its way, in total shadow, along the lip of the gorge directly opposite. I was concentrating on these clowns of the bushveld, hoping to spot an exciting composition.

I had been looking at the members of the troop for about 15 minutes when I noticed a straggler at the rear of the troop moving much more slowly and much more deliberately along the boulders of the opposite lip of the gorge.

I could see that this was a female – the engorged behind could not be missed. However, this baboon was bipedal, walking on her hind legs only. Peering through my telephoto lens, I could see that this female baboon had lost both of her hands. Her front legs ended abruptly – they seemed to have been severed in some accident, probably from a farmer’s gin or spring trap.

She did not seem to be too encumbered by her disfigurement as she ran at a trot on her two hind legs. My heart started pounding. What I was witnessing was a primeval scene; I thought immediately of the evolution of a human-like bipedal primate some 4 – 5 million years ago as witnessed in the spectacular fossil record of our ancestors in South and East Africa.

The spray from the waterfall that morning was heavy, frequently obscuring the opposite wall of the gorge. I managed to take only three snaps, the last one as the female was starting to run past a pool of water in a deeper nook of the canyon wall.

When I finally had a chance to look at these extraordinary images after the long journey home, the classical music of ‘In the Hall of the Mountain King’ resounded through my head:

Far away

In a land caught between

Time and space

Where the books of life lay

We fear

This castle of stone

The mountain king roams

All alone in here

But (s)he's not the only one

Lost inside

Forever hidden from the sun…

Edvard Grieg

THE WORLD OF WATER: A PERSONAL JOURNEY – Part III: Fresh Water

In a previous post I explained why water as a substance holds such fascination for me, particularly so as a photographer. As a child, I experienced real freedom, unfettered by over-protective parents – days spent out-of-doors in the immense Highveld grasslands, dry and dusty, far from home, in the company only of a small band of loveable rascals. Any encounter with water was a rare occurrence for us youngsters, be it a stream, a river, a dam or – on a few travels with our parents – the ocean. The coolness, the flow, water’s ceaselessly changing nature, its might, held us in thrall.

At school, I was taught that water, as a compound, is colourless and odourless. It took me quite a while to realise that the teachers were speaking of pure water, uncontaminated by any solutes and any suspended particles, a substance so pure that I had never been exposed to it. And, while the teachers were right, to me water has always remained a fascinating enigma. It is colourful by reflection and diffraction of sunlight or because it harbours cyanobacteria, algae and other organisms, or because it is mixed with countless other chemicals. It does smell too, again because water never occurs in its pure form in nature on our planet.

Water is weird. Although the atoms that comprise a water molecule (when taken together) are less massive than the atoms that make up a hydrogen sulphide molecule, water is liquid at room temperature rather than a gas. Water also clings: it coheres to itself (forming spherical raindrops and hailstones and suspended droplets on branches or grass culms following rain or dense mist) and it adheres to a multitude of other substances (a natural ‘glue’ that holds lumps of soil together, for example). Pure water has its highest density at 4°C, so that ice floats instead of sinking, and deep lakes never freeze all the way through to their bottom. Water heats up much more slowly, but, similarly, once heated, it also loses heat much more slowly than air or rock and sand. The presence of a large amount of water in the environment, either on the surface (as seas or large lakes), in the soil or stored inside vegetation (which also releases moisture into the atmosphere by evapotranspiration) tends to reduce the fluctuations in temperature of the terrestrial environment from day to night and from season to season. Water also has low viscosity, flowing easily down the slightest of slopes, or vanishing between the tiniest of cracks on rock or spaces in sandy soil. Moreover, water is a massive enough, incompressible liquid that scours, erodes, and sculpts even the hardest of rock surfaces.

As water evaporates from the vast surface of the oceans, clouds are formed and condensed water droplets, carrying no dissolved minerals, fall back to the surface as precipitation. Some of the moisture will be blown off course by winds and will fall, not back into the seas, but onto the solid surfaces of the islands and continents. This pure, fresh water will accumulate dissolved chemicals as it percolates downwards through the soil and porous rock strata, but it will never attain the much higher concentrations of solutes found in the oceans.

The water will continue to flow downwards, unless it is prevented from doing so by impervious rock strata. It will collect underground if trapped or it will emerge onto the surface of the slopes of the land as springs. From here it will continue its downward journey, forming rivulets and streams, or filling depressions in the landscape as pools and lakes.

As weird and wonderful as water is physically and chemically, for me it is the flow of this vital substance and its ability to reflect light that mesmerise. Silent, smooth, un-rippled and gentle in one instance, eliciting tranquil thoughts, moods and emotions; thunderous, dangerous, life-threatening on the next occasion, bringing forth excitement, bewilderment and even fear.

The speed and shape of the flow and the different colours of water seem interminable, and yet these bewitching phenomena are simply manifestations of the underlying action of the fundamental physical forces of the universe. The knowledge and experience that there exist substances, and interactions between substances, and actions of forces upon these substances and their interactions – actions and reactions, processes and patterns – that are at the same time fully explainable, determined and constrained by the forces of nature, and yet endlessly mutable as an outcome, to me have offered meaning, beauty and awe in equal measure throughout my life.

For humans and the vast majority of all the other terrestrial inhabitants of Earth fresh water is vital for continued existence. Only around 3% of the total quantity of water that can be found in the biosphere carries a dissolved mineral content low enough to be considered safe for the consumption by species that ply their trade on continents and islands. And this vital resource is diminishing rapidly as our own species continues to exploit and pollute any and all sources of fresh water on the planet surface, still believing, as we do, in ancient mythologies that professed that we, Homo sapiens, are the masters of it all and that Earth, and indeed the entire universe, exist because of us, for us. As our ceaseless slumber continues and we remain embedded and comforted by out-dated and misguided beliefs, as yet unpolluted, consumable sources of water are speedily becoming an exceptionally rare reserve planet-wide. And as this vital, life-supporting liquid dwindles on Earth’s surface, both in quality and quantity on our ever rapidly-heating planet, so too evaporate any hopes of a future for humankind that is meaningful, tolerable and peaceful. Fresh water is running out fast.

THE WORLD OF WATER: A PERSONAL JOURNEY – Part II: The Ocean and its Waves

For any alien traveller, Earth would be a beacon in the vastness of space. Of all the planetary bodies in our solar system, the blue marble we live on is the only one with liquid water covering most of its surface. It is common cause amongst biologists that the presence of liquid water is a sign for the possible existence of life on any planet in the universe. Therefore, to a traveller through space Earth stands out as a likely home for the organic complexity we call life.

Water covers over 70% of Earth’s surface, an expanse of approximately 361 million square kilometres. With an average depth of between three to four kilometres, the single ocean of our planet holds about 1, 34 billion cubic kilometres of water. So, a watery world indeed, but salty too. The ocean that comprises over 97% of Earth’s water has accumulated dissolved minerals throughout its more than four billion-year existence, so that of seawater’s mass today 3, 5% is made up of dissolved salts and other minerals.

Our planet’s single ocean forms over 90% of the biosphere, that thin, tenuous layer of the Earth’s surface that can sustain life. It is no surprise then that the ocean is home to more than 93% of all presumed life-forms on our planet. Presumed living species that is, because we have hardly bothered to explore this vast realm, most of which exists in complete darkness – sunlight can not penetrate seawater to a depth greater than a hundred metres or so. It is an indictment to the often-misguided human endeavour that we know less about our ocean than we know about the moon or the surface of Mars; we have explored only around 6% of this immense and vitally important region of our own home.

We owe our existence to the ocean. The first organisms, the first living beings, evolved in seawater between 3, 5 and 4 billion years ago. These are our ancestors. Since the evolution of photosynthesis, first be cyanobacteria and much later by algae, the surface waters illuminated by sunlight made available the production and release of oxygen into the atmosphere as a waste product of this process. For aeons algae have absorbed vast amounts of carbon dioxide from the atmosphere, thereby mitigating (up until recently in Earth’s history, that is) the accumulation of heat by the planet.

The majority of sunlight striking exactly half of the Earth’s surface at any moment in time irradiates the ocean. As the ocean surface heats up, currents and transfer of heat to the atmosphere redistribute this energy, driving the planet’s climate systems and thus doling out precipitation around the globe. Like a gigantic conveyor belt of energy, the ocean helps regulate Earth’s land temperatures, acting as coolant in summer and heater in winter. Without this global re-distribution of heat, surface temperatures on land would be unbearable for the substantial majority of terrestrial organisms.

Other than the fathomless immensity of the ocean, the most spectacular feature of this underappreciated waterworld are its waves. As the ocean is ruffled by the nudging and shuddering of the dynamic rocky planet on which it rests, and as it is whipped by winds of its own making, the surface water undulates. These wrinkles travel over the expanse of the ocean, the upper water column bobbing up and down as it is lifted into crests and dropped into troughs. When the undulations reach shallower water at the margins of islands and continents, as though wishing to greet the land first, the crests bend forward as a result simply of the deeper water slowing down as it rubs and scours over the ocean floor in these shallow zones.

For me personally, waves represent a myriad of marvels. The process of wave action is well understood scientifically; it is a continual process and relatively simple in mechanism. Yet each wave is unique. The encounter of each wave while ‘wave-watching’ is unique too. The experience ranges from perception of the susurrations of gentle wavelets lapping at sandy beaches to the thunderous cacophony of invincible titans assaulting the very continents themselves. Depending on the time of day, the quality of sunlight, the mood of the tides, and the weather, my experiences and the concomitant thoughts and emotions provoked by the watching of waves flit from tranquil bliss to atavistic fear. And all the while the waves remind me of my own, very special history on Earth: from my ocean-borne ancestors billions of years ago to my present insignificance on this unique planet, Earth.

THE WORLD OF WATER: A PERSONAL JOURNEY - Part I: Introduction

As I near rapidly the completion of my sixth decade of tenure on our Earth, I feel more and more compelled towards introspection: to make sense of what has happened, what I have experienced and how I have reacted to such experiences. Of course, my own journey represents only an infinitesimal fraction of the experiences of all members of a particular and peculiar species, Homo sapiens – never mind the experiences of millions of other species that have been and are inhabitants of this singular planet.

My own personal reminiscences represent at best a wisp of time, a miniscule crumb of place – nostalgias that are so insignificant as to make thinking or writing about them seem supremely self-important. Yet, there remains this compulsion deep within me, to ponder, to think, to express and to share these recollections. I do not believe that this is arrogance: if anything, I stand humbled and in complete awe of the universe as a whole, and particularly of this planet I may call home and its myriad denizens.

I was very privileged to grow up in a house on the edge of a suburb. Looking out from my bedroom window, I was faced, not by a neighbour’s dwelling with tended lawns and flowerbeds, but by a sizeable patch of South African veld. ‘Veld’ has various meanings in southern Africa: it can refer to bushveld (savannah) or to grassland; it can incorporate kopjes (boulder-strewn hills) or rante (rocky ridges); it can be undulating or flat. It did not matter to me at all what kind of veld I was playing in or trudging through as a child; the veld became my spiritual home at a very young age.

South Africa is a water-poor part of the African continent. Where I grew up on the Highveld (a vast plateau in the interior of the country covered in grassland), the winters were dry – up to five months of clear blue skies with no rain at all. Brown, dusty, fire-prone grasslands. When, as kids, we did stumble across water of any kind, our delight was expressed fully: mud-fights in shallow pans, crab-hunting along rivulets, or bathing in deep, rocky pools on a hot summer day were all part of childhood and early adolescence.

The contrast between the veld in all its facets and the watery worlds made an impression on me from very early on. The world of water was fluid; the veld was solid. The colour palette of the veld was striking and beautiful, but it paled when compared to the ever-changing palette of the world of water. In this rare world on the Highveld, the liquid world, there was flow – swift movement and rapid observable changes when compared to the terrestrial realm.

Thus my fascination with two worlds in particular: the African veld and its inhabitants, and the world of water in all of its forms – rain, mist, ponds, pans, rivers and oceans, and clouds too.

In the next four instalments of this series, I will be looking a little more closely at this most magnificent World of Water.