Stratosphere

“ The convectional layer of air—that is, from ground level to stratosphere—is marked by constant motion as noted, the movements consisting of general circulation, local winds and the turbulence connected with vertical movements. There seems to be no such complexity of movement in the stratosphere; indeed the knowledge of the movements of the air in the stratosphere is next to nothing. ”

“ His discovery of the so-called isothermal layer, or stratosphere as it is now generally called, will always stand out as one of the most important events in the study of the upper atmosphere. He also carried out investigations in Sweden and over the Zuider Zee, the Mediterranean and the tropical region of the Atlantic, and fitted out a special vessel in order to study the currents above the trade-winds. ”

“ The atmosphere may be subdivided vertically into a number of atmospheric layers, but the most common basic subdivision is that which recognizes a troposphere from the surface to about 10 kilometers, a stratosphere from about 10 kilometers to about 80 kilometers, and an ionosphere above 80 kilometers. ”

“ At the top of the troposphere is the tropopause, a very thin layer marking the boundary between the troposphere and the layer above. The height of the tropopause and certain weather phenomena are related. Chapter 13 discusses in detail the significance of the tropopause to flight. Above the tropopause is the stratosphere. ”

“ Else why did it climb so high into the stratosphere? It was far beyond the reach of ordinary planes. High trajectory projectiles had slight chance of hitting it, even if it were visible. What then was its vulnerability, which this hiding seemed to indicate? They must know within twenty-four hours. ”

“ But the strange heavens of the later autumn, the fiery glow of sunrise and sunset, the brownish haze that girdles the sun all day, are phenomena so out of the range of common experience that at first all the experts in meteorology were at sea in their explanations. At the outset, many of these students of the atmosphere turned naturally to the conjecture that some of the vagrant matter of space, such as we see in the comets or dust-like meteors, had been drawn down upon our atmosphere, and so enveloped the earth with a meteoric mist. ”

“ The nearer the stratus-cloud to the earth, the [Pg 284] greater the displacement of surface atmosphere, the lower the barometer, and, ordinarily, the more violent the wind. First, because the same intensity, which, by attraction, brings the trade near the earth, acts with greater force upon the surface atmosphere; and, secondly, the storm winds, which are often most rapid beneath the clouds and above the earth, are likely to be felt with more violence at its surface, where the stratus cloud runs low, especially at sea. ”

“ The clouds not only promote the precipitation which takes place in this region, but they also cause the rains to fall on places where they are most required, shading the surface from which the heating rays of the sun are to be excluded, and thus giving tone to the atmospherical circulation of the world and vigour to its vegetation. You have often, when the sun is sending his rays with great heat down on the earth, seen the atmosphere dancing, as it were, and trembling. ”

“ No dust is lifted high into the air to lend it a distinct colour; Only the dazzling white reflex from the clouds reaches the outside space and gives the planet its remarkable, brilliantly white, lustre. The powerful air currents in the highest strata of the atmosphere equalize the temperature difference between poles and equator almost completely so that a uniform climate exists all over the planet analogous to conditions on the Earth during its hottest periods. ”

“ This objection has no weight, because the Earth controls not only all the objects fixed to the soil, but also the atmosphere, and the clouds that surround it like a light veil, and all that exists upon its surface. The atmosphere, the clouds, the waters of the ocean, things and beings, all are adherent to it and make one body with it, participating in its movement, as sometimes happens to ourselves in the compartment of a train, or the car of an aerostat. ”

“ Some lengthened bands along the disc, real clouds formed in the midst of a very confined atmosphere, from which emerged not only all the mountains, but also projections of less importance; its circles, its yawning craters, as capriciously placed as on the visible surface. Then immense spaces, no longer arid plains, but real seas, oceans, widely distributed, reflecting on their liquid surface all the dazzling magic of the fires of space; and, lastly, on the surface of the continents, large dark masses, looking like immense forests under the rapid illumination of a brilliance. ”

“ I like to think of the philosophic and speculative atmosphere as no mere gas-zone of forty-five miles' depth, as of old, but as an envelope of intense kinetic life, in the denser zone, where the logical molecules touch one another with marvelous frequency, and where there is frictional contact with the solid but rather inert lithosphere. ”

“ The transparency of the atmosphere,—a quality so essential to fine views of the starry heavens,—is much increased by containing a large proportion of water, provided it is perfectly dissolved, or in a state of invisible vapor. A country at once hot and humid, like some portions of the torrid zone, presents a much brighter and more beautiful view of the moon and stars, than is seen in cold climates. Before a copious rain, especially in hot weather, when the atmosphere is unusually humid, we sometimes observe the sky to be remarkably resplendent, even in our own latitude. ”

“ In the lower atmosphere the vapour of water is present in a varying quantity, in the average about one per cent. in weight, with a volume depending on the temperature. Dust is always suspended in the atmosphere; the coarser particles settle, but the finer ones, that come from volcanoes, may float for a long time in the high atmosphere. Dust is an important factor in the production of clouds and rain, and occasions many optical phenomena.
[Pg_26]
Plate II.—Optical Phenomena showing the Height of the Atmosphere. ”

“ Under the sky was stretched a network of white threads, a network fine and close-meshed, where here and there were caught thicker white vapours of globular shape; and to the eastward, above the ragged barrier of the forests, surged the summits of a chain of great clouds, growing bigger slowly, in imperceptible motion, as if careful not to disturb the glowing stillness of the earth and of the sky. ”

“ The atmosphere is now unable to sustain the moisture which is diffused throughout it, either chemically or mechanically: the clouds lower, and the rain falls, and passes to the lowlands. When, however, the mountains increase their power of attraction, then the elasticity of the air is again restored, and two important phenomena result. First of all, the mountains collect around their summits vast masses of clouds, hold them fast and firm above themselves like second heads, until, as determined by the contest of electrical forces within them, they pour down as thunder-showers, rain or mist ”

“ The land, north and south, is made habitable by the clouds. They gather their burdens of vapour from the warm seas, the wind drifts them north and south, where they let it fall in rains that make and keep the earth green and beautiful. From the clouds the earth gathers, like a great sponge, the water that stores the springs and feeds rivers and lakes. How necessary are the winds that transport the cloud masses!
The air is the breath of life to all living things on our planet. Mars is one of the sun's family so provided. Plants or animals could probably live on the planet Mars. ”

“ That lower stratum of the heavens occupied in the previous vision by seething steam, or gray, smoke-like fog, is clear and transparent; and only in an upper region, where the previously invisible vapor of the tepid sea has thickened in the cold, do the clouds appear. But there, in the higher strata of the atmosphere they lie, thick and [Pg 208] manifold,—an upper sea of great waves, separated from those beneath by the transparent firmament, and, like them too, impelled in rolling masses by the wind. A mighty advance has taken place in creation ”

“ If we conceive the entire globe spotted with high and low areas, we may picture the air surging upward in the lows, flowing outward under the isothermal layer, descending 374in the highs, then flowing outward along the earth’s surface toward the lows in a continuous cycle. Thus, chiefly is maintained the vast and multifold circulation of the atmosphere over the entire world. ”

“ B. Since so large a portion of the atmosphere, as is over the torrid zone, is in continued agitation, these agitations in an elastic fluid, which yields to the slightest impression, must extend every way, to a great distance; the air, therefore, in all climates, will suffer more or less perturbation, according to the situation of the country, the position of mountains, valleys, and a variety of other causes: hence it is easy to conceive, that almost every climate, must be liable to variable winds ”

“ In most landscape negatives there is a want of atmosphere48 (by which we mean the haze always present in the air) in the distance and middle distances, and we have found that by applying one piece of tissue-paper to the back of the negative to cover the middle distance and distances, and another to cover the distance alone, atmospheric effect is produced. The effect of atmosphere is usually shown by grey tones as compared with those of the foreground, and the greyer they are the more distant should the objects be away in nature. This effect is accomplished by the tissue-paper. ”

“ It has been asked whether a study of the solar atmosphere may not throw some light upon the peculiar constitution of the upper strata of the earth's surface, which are known to be of less density than the average interior of our planet. ”

“ THE ATMOSPHERE COVERS THE LAND AS WELL AS THE OCEAN. On land its electrical condition, its temperature, its humidity, and its movements, are, doubtless, subject to more rapid and complicated changes than on the sea. The effects only of these influences can be noticed by the mariner.
The originating causes are on shore. Hence to understand the phenomena of the atmosphere, or to profitably study its laws, it must be studied as a whole. ”

“ From the peculiar properties of air in its relation to heat, the atmosphere has a tendency to form itself into heterogeneous strata, more or less inclined to the horizon; each stratum having a horizontal motion independent of the others—a fact the significance of which, I think, is frequently lost sight of by meteorologists, more especially by cyclonologists. ”

“ And thus the wonderful march of the most powerful steam-engine with which we are acquainted, the atmosphere, appears to be permanently regulated. The irregular distribution of physical qualities over the earth's surface is here seen to be a preserving principle for terrestrial life. ”

“ ATMOSPHERIC OPTICS When we look up into the sky on a cloudless day we behold a continuous canopy, the prevailing color of which is blue. This canopy is a veil that hides the starry hosts beyond, and its presence seems, at first sight, incompatible with the fact that the air is a transparent medium. We see the stars by night through the same intervening atmosphere. Why are they cut off from our sight by day? ”

“ The uses of the atmosphere are many. It is the medium for regulating the dispersion of watery vapours over the earth. If there were no atmosphere, and that, as now, the equatorial climes were hot and the poles cold, evaporation would be continually going on at the equator, and condensation in the colder regions. The sky of the tropical climes would be perpetually cloudless, whilst in the temperate and arctic zones we should have constant rain and snow. ”

“ We thus have an insight into the operations which are going on in the equatorial belt of precipitation, and this insight is sufficient to enable us to perceive that exquisite indeed are the arrangements which Nature has provided for supplying this calm belt with heat, and for pushing the snow-line there high up above the clouds, in order that the atmosphere may have room to expand, to rise up, overflow, and course back into its channels of healthful circulation. ”

“ But while the atmosphere may be considered generally as an aerial zone of the earth, the companion of the massy spheroid in its annual revolution round the sun, and rotating with it upon its axis, it has independent movements which present very complex phenomena, however clear the causes which put them in operation. The particles of air are constantly suffering displacement, and it is easy to conceive of various circumstances disturbing the dilatable and elastic fluid in which we live. ”

“ From the earliest ages clouds have attracted the attention of observers. Varied are their forms and colours, yet in our atmosphere there is one law in their formation. Cloud-particles are formed by the condensation of water-vapour on the dust-particles invisibly floating in the atmosphere, up to thousands—and even millions—in the cubic inch of air. ”

“ Underneath the cloud-veil the air was absolutely clear and transparent, clearer, indeed, than terrestrial air at the highest elevations reached by mountain-climbers, and, moreover, it seemed to be endowed with a strange, luminous quality, which made objects, no matter how distant, stand out with almost startling distinctness. ”