Lost Woods: The Discovered Writing of Rachel Carson - Rachel Carson, Linda Lear (1999)
Chapter 23. Clouds
TELEVISION WAS A NEW MEDIUM for writers in the 1950s, and Carson was not initially enamored of its creative merits. She did, however, recognize television’s potential educational value.
When the idea for a show on clouds was proposed by an eight-year-old viewer of the CBS show Omnibus who wanted to see a program on “something about the sky,” the Ford Foundation’s TV-Radio Workshop approached Carson to write a television script on clouds. She agreed to collaborate with the Omnibus producer and with meteorologist Vincent Schaefer, who had discovered the process of cloud seeding and whose film footage formed the cinematic basis of the show. Her objective was to change the popular conception that cloud types and formations had no particular scientific significance, and to provide an awareness of a dynamic process that linked clouds to the broader web of life. The resulting script was vintage Carson, with an emphasis on the long journey of wind and water in a constantly renewing and unending cycle. This venture deeper into the science of weather and climate renewed her interest in writing on the subject of global climate change.
“Something about the Sky” aired on CBS Omnibus on March 11, 1957, and Carson and her family gathered around her brother’s television set to watch her first successful endeavor in an unfamiliar medium. Several days later, Carson capitulated and bought her own television set.
(Clouds drifting by, of various types, but all in motion)
AMONG THE EARLIEST MEMORIES of each of us are the images of clouds drifting by overhead,
fleecy, fair-weather clouds promising sunny skies -
storm clouds bringing portents of rain or snow.
The farmer plowing his field reads the weather language of the sky.
So does the fisherman at sea, and all others who live openly on the face of the earth.
In those of us who live in cities, awareness of the clouds has perhaps grown dim; and even those who live in open country may think of them only as a beautiful backdrop for a rural scene, or an ominous reminder to carry an umbrella today.
The clouds are as old as the earth itself - as much a part of our world as land or sea.
They are the writing of the wind on the sky.
They carry the signature of the masses of air advancing toward us,
across sea or land.
They are the aviator’s promise of good flying weather, or an omen of turbulent air.
Most of all they are the cosmic symbols of a process without which life itself could not exist on earth.
II. The Ocean of Air
Today we are going to look at clouds as perhaps we have never looked at them before.
We are going to pretend we live on the bottom of an ocean - an ocean of air in which clouds are adrift -
just as sponges and coral and spidery crabs inhabit the floor of the water ocean.
But it will not be hard to pretend that, for in fact that is just what we do. In relation to the air ocean, we are exactly like deep-sea fishes, with all the weight of tons of air pressing down upon our bodies.
And there are other similarities.
Our world is divided into three parts: earth, sea, and air.
Out there is the ocean of water - familiar, though always mysterious.
Its greatest depths lie 7 miles down.
From surface to bottom pressure increases, from 35 pounds
to the square inch at the surface to 7½ tons in the greatest depths.
Waves move across it. Great currents flow through it like rivers.
Up there is another ocean - the air ocean that envelops the whole globe.
Its depth, from airless space down to where it touches earth, is some 600 miles.
Like the water ocean, its substance becomes more dense
from surface to bottom. Only the lowermost layers are
dense enough to support life.
Living on the bottom of this ocean of air, we support on our bodies a pressure of about a ton to the square foot of surface.
In this lower layer, too, clouds are born and die.
Like the sea, the atmospheric ocean is a place of movement
and turbulence, stirred by the movements of gigantic waves - torn by the swift passage of winds that are like ocean currents.
Now that we are learning to read the language of the sky, we can interpret much of the structure of our air ocean by looking at the pattern of the clouds.
Look, for instance, at this ribbed pattern of high clouds.
Remember that they are perhaps 8 or 10 miles above us, and so the cloud bands that look rather close together are in reality perhaps 20 miles apart.
Like white caps on the crests of ocean waves, these clouds mark the crests of gigantic atmospheric waves - waves surging through space in an undulating pattern.
The bands of cloud mark the upsurges of condensation; the
wave troughs of blue sky, the warmer air valleys of evaporation.
Clouds give other clues to the unseen structure of the ocean of air.
Aviators know the danger of flying in mountainous country, where savage downdrafts in the lee of high peaks may suddenly snatch a plane out of the sky.
The science of clouds is now showing how warning signals are hung out in the sky for all to read them.
When strong winds strike a mountain, the atmosphere up to a height of thousands of feet above the land is thrown into a strong wave motion which extends out over miles of valley on the lee side.
Clouds form on the crests of these atmospheric waves -
the strange, almond-shaped lenticular cloud.
So mobile it seems a living thing, the cloud nevertheless maintains its fixed position at the crest of the air waves, neatly balancing condensation and evaporation, built up on the windward side and eaten away on the lee side.
Lenticular clouds scattered out over the valley on the lee
side of a mountain range are signs to the pilot of dangerous turbulence.
Here again the clouds are writing a story of violent movement within the atmosphere.
Winds that rush down mountain slopes are known the
world over -
the foehn wind of the Alps - the chinook of the Rockies -
the zonda of the Andes.
As moist air is carried up and over a mountain peak by strong winds, cloud is formed and pours over the crest of the mountain like a waterfall - the foehn wall or foehn cloud.
Here again the flier who can read the clouds stays clear.
These are among the spectacular features of the aerial drama -
to which we shall later return. But meanwhile, what of the basic meaning of the clouds - what is their role in the life of the earth?
For us, as living creatures, they are one of the reasons we
are men instead of fishes. As land creatures, we must have water.
Without clouds, all water would remain forever in the sea, from which our early ancestors emerged 300 million years ago.
Without the miracle of clouds and rain, the continents
would have remained barren and uninhabited, and perhaps life would never have evolved beyond the fishes.
III. The Water Cycle
Almost all of the earth’s water is contained in the oceans that encircle the globe - all but a mere three percent.
But to us, inhabitants of the land, that three percent is vital.
It is engaged in a never-ending cycle of exchange: from sea to air - from air to earth - from earth to sea.
Water from the sea is constantly being brought to the land.
There it makes possible the existence of plants and animals.
There, in streams and rivers, it carves and molds the face of the land, cutting valleys, wearing away hills.
Over all the vast surfaces of the ocean, stirred and broken by the wind, molecules of water vapor are escaping into the overlying air.
This occurs everywhere to some extent, but in the warm tropical seas on each side of the Equator - the belt where the Trade Winds blow - the escape of water vapor into the air is tremendous.
The warm, moist air rises; in the cooler air aloft it condenses.
Processions of woolly cumulus clouds are set drift in the trade wind.
The moisture in these clouds may fall as rain and be recondensed several times, but it eventually becomes part of the vast circulation of the upper atmosphere - drifting over the continents - embodied in the clouds that day after day move from horizon to horizon.
Then in a drama of turbulence and change hidden within the heart of the clouds, the water vapor begins to return to the liquid state - begins to drop earthward with increasing momentum.
Rain falls on the earth -
the end of a long journey that began in a tropical sea;
yet in a constantly renewing cycle there is no end, as there is no beginning.
Stage succeeds stage, turning again and again upon itself like a wheel.
Or, in the cold regions, snow -
a deep, soft, sound-absorbing blanket bringing a great quiet to the earth; storing moisture that will be released gradually to the thirsty land.
From the run-off of high ground - from melting snowfields and glaciers,
the water finds its way to the streams:
the noisy hill streams tumbling over rocky beds -
the quietly rolling waters of the valleys and plains -
all to return at last to the sea.
Sometimes the process is marked by the violence of storms sometimes Nature indulges in the wild fury of floods -
But often the cycle brings us nothing more troublesome than a gentle April rain - and always it is in the main a beneficent process,
bringing the continents to life.
IV. Cloud Forms
What of the clouds themselves - the aerial agents of this cosmic process?
Someone has said that without the gift of sight, one could never imagine clouds - their beauty, their ever-changing shapes, their infinite variety of form.
Rolling, swirling along the floor of the air ocean are the lowest clouds of all - fog.
For fog is nothing but a stratus cloud so near the earth that sometimes it touches it.
Fog may shut down quickly over a clear autumn night when
the air over the land loses its heat by rapid evaporation into the open sky.
Such a fog is a shallow one; though we earth-bound mortals grope blindly through it, the tops of tall trees may clear it, and in the morning the sun quickly burns it away.
Fog of a different sort forms when warm sea air rolls in over colder coastal waters and over the land -
shutting down harbors -
grounding planes -
isolating ships at sea with its soft grey swirling mists.
When a fog drifts at a height of a thousand feet or so, forming the aviator’s “ceiling,” it is really a layer cloud called stratus.
As we fly above it, it is a veil through which the earth is seen dimly, like the shallow bottom of a bay when one looks down from an idling skiff.
Or it may stretch away to the plane’s horizon like a monotonous Arctic icefield.
Compared with the high-drifting cirrus wisps and the soaring columns of the cumulus, the stratus clouds are the duller earthlings - coarse-textured clouds formed of large water droplets.
Most beautiful in the infinite variety of their shapes are the cumulus clouds.
These are also the clouds that generate the most incredible violence known on earth - for beside the power of a tornado or a hurricane even the atomic bomb is insignificant.
The birth of a cumulus cloud is relatively peaceful and simple.
As the earth warms under the morning sun, it heats unevenly.
Invisible columns of warm air begin to rise - from a plowed field, a lake, a town - any area warmer than its surroundings.
The column of rising air contains invisible molecules of water vapor drawn from vegetation, evaporated from the surface of earth or water.
Such warm air can hold quantities of water in the vapor state.
Rising, it cools; at a certain point it can no longer contain its water invisibly; and the white misty substance of a cloud is born.
Broad-winged birds like hawks and eagles find these soaring “thermals” and ride them for hours.
Glider pilots seek them out, locating them by the clouds at their summits.
Polynesian navigators steering across the South Pacific from atoll to atoll, find their way by the cloud rising like a kite from each pinpoint of warm land.
Most cumulus clouds have straight-edge bases, as though evened off by the stroke of a cosmic knife -
but the shaping blade is the altitude that marks a sharp change to cooler temperature -
below this line the air column holds its vapor invisibly -
once above it, all the water molecules blossom, through condensation, into the fabric of a cloud.
In regions of very warm, moist air, the atmosphere is in the power of highly unstable forces.
Then a cumulus cloud puffs up and up to extraordinary heights.
When the tornado of June 9th, 1953, approached the city of Worcester, Mass., observers at MIT reported that the
clouds towered right off the radar screens, which could register only to altitudes of 50,000 feet.
Even higher clouds are known from the true tornado country of the middle west -
70,000-foot giants more than twice as high as Everest.
Most ethereal and fragile of all are the high-floating wisps of cirrus, drifting just under the stratosphere.
If we could approach them closely in an airplane we would
find them glittering in iridescent splendor like the dust of diamonds.
Up in these substratospheric vaults of sky, from which the
earth looks like the sphere it is,
there is a hard, bitter cold, far below zero, summer and winter.
So the cirrus clouds are composed of minute crystals of ice -
the merest specks of substance, so thinly spread through the sky that not more than 2 or 3 occupy a cubic inch of space.
It is the high-riding cirrus that first beholds the sunrise, or in evening holds the light of sunset longest, reflecting back to the dark earth the splendor of a light no longer visible -
the rose and gold, the wine and scarlet of the sun.
The cirrus clouds are the birthplace of the snow,
slowly cascading down to earth in long, curving streaks as the crystals fall behind the swift winds of the upper sky. Halos seen around the sun or moon are the ice crystals of a cirrus veil called cirro-stratus.
Like the lower clouds, cirrus is formed of water vapor that is drawn from the sea and pumped aloft in the swift updrafts
of cumulus clouds - or that rides up an ascending elevator
of warm air slipping over a cold front.
Sometimes cirrus is born of material torn from the top of high cumulus by the strong winds of the upper air - winds that tear off the crests of the clouds as, at sea, a gale blows off the wave crests and sends the spindrift scudding away over the water.
Sweeping curls of cirrus indicate the passage overhead of a rushing current of air, pouring through the sky at a speed of two or three hundred miles an hour. [ … ]
Ed.: Carson ends the script with the story of jet streams, the strongest of all winds, and conjectures that the forces that direct the jet stream will be “found in the far depths of the sky [and] written in the clouds.”