Weather Proverbs and their Justification

June 1 1911

Weather Proverbs and their Justification

June 1 1911

Weather Proverbs and their Justification

“ So it falls that all men are

With fine weather happier far”’

—King Alfred.

THIS thousand-year-old observation by England’s wisest ruler recognizes the fact that fine weather induces good tempers, and therefore amply justifies the proverb that shrewdly bids one “Do business with men when the wind is in the northwest.”

But this effect on the minds of men, says W. J. Humphreys in the Popular Science Monthly, does not exhaust the good and the evil of weather conditions, since our comfort, our convenience and even the success or failure of whatever we undertake, all depend in large measure upon clear skies and cloudy, upon wind and rain, and upon everything that renders the elements fair or foul.

Because, tuen, of the great influence weather conditions have over human affairs numerous rules for foretelling their coming changes have been formulated in all ages and by all peoples. While many of these rules are of general application, many others, as might be suspected, have only a local value, and owe their justification to some peculiar configuration of mountain and valley, or distribution of land and water, and, therefore, when transferred to other places commonly are meaningless, if not even misleading. Nevertheless, all of them, the wise and the silly, the good and the bad, have been inherited alike from the ends of the earth; and in this way many a concise saying has become a weather nugget in that great vein of wisdom and folly called folk lore.

Some of these nuggets are as pure gold, for they correctly state the actual order of sequence, as determined by innumerable

observations, even when the cause for such an order was not in the least understood by those who discovered it ; but most of them are only as fools’ gold, pretty in form, but wholly deceptive. To this latter class belong hundreds of proverbs of the ground-hog and gosse-bone type; some owing their origin to one thing and some to another, but, like predictions based upon the weather of saints’ days, or upon the phase of the moon and the pointing of its horns, never for a moment accepted by those whose reason demands an adequate cause for every effect.

But that other class of weather proverbs, those that do have more or less to support them, is worthy of very careful consideration and study, for they embody accurate descriptions of phenomena and express the usual sequence of events.

It can be argued, of course, and apparently with good reason, that, in spite of its scientific interest, such a study can not now have any practical use, since nearly every country has a national weather service whose forecasts, for any given time and place, are reliably based upon the known immediately previous conditions all over a continent—conditions that are followed from hour to hour and day to day; that are minutely recorded and carefully studied.

It is true that when one is supplied with such information his horizon becomes world wide ; that he sees the weather as it is everywhere; knows in what directions the storms are moving and how fast, and that, therefore, he can predict the approximate weather conditions for a day or more ahead. But, in general, it is not practicable officially to forecast for definite hours, nor for particular farms and vil-

lages. In the making, then, of hour-tohour and village-to-village forecasts, though often of great value, one must rely upon his own interpretation of the signs before him. Besides, in many places it is impossible to get, in time for use, either the official forecast or the weather map upon which to base one’s own opinions, and under these conditions certain weather signs are of especial value—signs which every one uses to a greater or less extent, but with an understanding of their significance that, according to such experience as only real necessity can give, varies from the well nigh full and complete to the vague and evanescent.

Thus the fisherman to-day, as in the past, will weigh anchor and flee from the gathering storm when to the uninitiated there is no indication of anything other than continued fair weather; and the woodsman, as did his remotest ancestors, will note significant changes and understand their warning messages when the average man would see no change at all, or, if he did, would fail to comprehend its meaning.

The prescience of these men is phenomenal, and it is with some of the useful weather proverbs they know so well, the causes of the phenomena they describe and the relation of these phenomena to others they precede, that the following is concerned.

SEASONS.

(“A good year is always welcome.”)

Naturally every one asks: “What of the coming season?” And especially is this an important question for the farmer, for a correct answer to it would tell him what crops to plant and where; whether upon hill or lowland, in light or heavy soil, and how best to cultivate them—vital points, every one, for his success. But whatever we may hope ultimately to accomplish, seasonal forecasting to-day is beyond the pale of scientific meteorology, though proverb meteorology is full of it. However, a few of the seasonal proverbs that deal with results rather than types of weather are rationally founded.

Among them we have:

“Frost year,

Fruit year.”

“Year of snow,

Fruit will grow.”

Or in still another form:

“A year of snow, a year of plenty.” That these and similar statements commonly are true is evident from the fact that a more or less continuous covering of snow, incident to a cold winter, not only delays the blossoming of fruit trees till after the probable season of killing frosts, but also prevents that alternate thawing and freezing, so ruinous to wheat and other winter grains. In short, as another proverb puts it,

“A late spring never deceives.”

A different class of proverbs, but one meaning practically the same thing as the foregoing, and justified by substantially the same fact, that is, that an unseasonably early growth of vegetation is likely to be injured by later freezes, is illustrated by the following examples:

“January warm, the Lord have mercy I” “If you see grass in January,

Lock your grain in your granary.” “January blossoms fill no man’s cellar.” “January wet, no wine you get.” “January and February,

Do fill or empty the granary.”

“All the months in the year Curse a fair Februeer.”

There are hundreds of other proverbs dealing with seasonal forecasts, but, except those belonging to such classes as the above, they have very little to justify them. Many are purely fanciful and others utterly inane.

SUN.

“Above the rest, the sun who never lies, Foretells the change of weather in the skies.—Virgil.

While proverbs concerning the seasons, in the most part, are built upon the shifting sands of fancy and of superstition, many, but not all, of those that concern the immediate future—the next few hours, or, at most, the coming day or two—are built upon the sure foundation of accurate observation and correct reasoning. Among these, perhaps the best are those that have to do with the color of the sky and the appearance of the sun, the moon and the stars, for we see the first because of our atmosphere, and the others through it and, therefore, any change in their appearances necessarily means changes in the atmos-

phere itself—changes that usually precede one or another type of weather.

A familiar proverb of this class runs as follows :

“A red sun has water in his eye.”

Now the condition that most favors a red sun is a great quantity of dust—smoke particles are particularly good—in a damp atmosphere. Smoke alone, in sufficient quantity, will produce this effect, but it is intensified by the presence of moisture. The blue and other short wave-length colors, as we call them, of sunlight are both scattered and absorbed to a greater extent by a given amount of dust or other substances, such as water vapor, than is the red ; and this effect, since it is proportional to the square of the volume, becomes more pronounced as the particles coalesce. Hence, when the atmosphere is heavily charged with dust particles that have become moisture laden, as they will in a humid atmosphere, and therefore relatively bulky, we see the sun as a fiery red ball. We know, too, that this dust has much to do with rainfall for, as was first proved many years ago by the physicist Aitken, cloud particles, and, therefore, rain, will not, under ordinary conditions, form in a perfectly dust-free atmosphere, but will readily form about dust motes of any kind in an atmosphere that is sufficiently damp.

A red sun, therefore, commonly indicates the presence of both of the essential rain elements, that is, dust and moisture ; and while the above is not the whole story, either of the meteorological effects due to dust in the air, or of the formation of rain, it is sufficient to show how well founded the proverb under consideration really is. And also this other one that says:

“If red the sun begin his race,

Be sure the rain will fall apace.”

SKY COLORS.

“Men judge by the complexion of the sky

The state and inclination of the day.” —Shakespeare.

There are many proverbs, ranging from the good and useful to the misleading and absurd, concerning the color of the sky at sunrise and sunset.

From Shakespeare we have the wellknown lines:

“A red morn that ever yet betokened Wreck to the seaman, tempest to the field, Sorrow to the shepherds, woe unto the birds,

Gusts and foul flaws to herdsmen and to herds.”

Besides these stately verses there are many proverb jingles that express substantially the same idea. One of them puts it thus:

“Sky red in the morning Is a sailor’s sure warning;

Sky red at night Is the sailor’s delight.”

But in many ways the most interesting of all those proverbs that have to do with red sunrise and red sunset is the one which, according to Matthew, Christ used in answer to the Pharisees and Sadducees when they asked that He would show them a sign from Heaven.

“He answered and said unto them, When it is evening, ye say, It will be fair weather: for the sky is red.

“And in the morning, It will be foul weather to-day: for the sky is red and lowring.”

It would seem, too, that Christ sanctioned these views, for it does not appear reasonable that He would teach by illustrations which He knew to be false. Then, too, He follows the above with these words: “O ye hypocrites, ye can discern the face of the sky; but can ye not discern the signs of the times?”

But whether or not Christ accepted these weather signs as being good, we feel certain that those to whom he spoke must have known and believed in them. It is, therefore, worth while to search, even though the search be a somewhat tedious one, for the physical explanation of these phenomena, and to see how it is possible, if it really is, for identically the same colors of the sky to have for the evening one meaning, and for the morning another entirely different. ^

To clear the way for this explanation itis necessary, first, to tell something of the composition of sunlight, and a little about the atmosphere through which it passes on its way to the surface of the earth.

We know that rain drops are colorless, and we know, too, that when we are between a falling shower and the bright sun they give us the exquisite coloring of the

rainbow. We are also aware that prismshaped, colorless and transparent objects will receive a ray of white sunlight and emit all the rainbow’s brilliant hues, from the faintest violet to the deepest ruby ; and that when these are recombined the result is white light like the original. Through such experiments and observations we infer that sunlight is composed, in part at least, of all pure colors, and that they gradually merge the one into the other.

Again, it is possible to obtain two sources of light of the same color and intensity such that at certain places they produce more than twice—in fact up to fourfold—the intensity of one alone, and at certain other places intensities less than that of just one, even to utter darkness. Now this tells us that in some respects two lights behave in a manner similar to two trains of water waves, for these may combine so as at some places to produce exceptionally large waves and at others practically smooth water. Indeed, it has been shown by numerous experiments that light has several properties in common with water waves ; one of these being wavelength, that is, the distance from a point in one wrave to the corresponding point of its nearest neighbor, as, for instance, from crest to crest.

Of all colors, violet light has the shortest wave-length, and red the longest. Blue is next to violet, yellow next to red, and green about an average of all. The wavelength of red light is less than twice that of the violet, and yet it would take more than 30,000 of the longest waves to which the eye is sensitive to span a single inch.

Turning, now, our attention to the atmosphere, we find that at nearly all times, and everywhere within two miles of the surface, and probably much higher still, it contains, in every cubic inch, thousands of dust particles coming from fires, from plants, from the dry earth as caught up by winds, and from still other sources. Much of this dust is excessively fine and settles down with extreme slowness. It serves, as already explained, as nuclei about which the myriads of cloud droplets are formed.

In addition to this important function, extremely fine particles of dust, and even single molecules, but not the coarser portions, as shown many years ago by Lord Raleigh, both scatter and absorb light of

all colors according to the laws: (1) that the amount, both of absorption and of scattering, decreases in the same proportion that the fourth power of the wavelength increases; (2) that both increase with the number of particles per unit volume, and with the average square of the volume of the individual particle.

The refractive index of the air and of the foreign substances it contains, together with certain numerical terms, also enter into the complicated equations that deal quantitatively with atmospheric absorption and scattering of light. These latter facts, since they are not essential to what follows, are mentioned here only for the sake of completeness.

Now, scattering and absorption, acting according to above laws, combine to give us the colors of the sky, because sky light is only the residual, after absorption, of that portion of sunlight which was scattered by the molecules of the atmosphere and by the foreign substances floating in it.

Since, according to the first law, but little light of very long wave-length is scattered while nearly all of exceedingly short wave-length is “absorbed, it follows that the light of maximum intensity, or the prevailing color, must have some intermediate wave-length. Hence the sky overhead is neither red (long wave-length) nor violet (short wave-length). Also, from the second law, we see that different parts of the sky at the same time, and the same parts of the sky at different times, will have different colors owing to the amount, aggregation and distribution of atmospheric dust.

When these particles are relatively few and small the prevailing color is blue. On the other hand, where the dust motes increase in size and number, as they do near the surface of the earth, or in size only, even at the expense of numbers, as happens in a moist atmosphere, because of their hygroscopic property, light of the shorter wave-lengths becomes more completely absorbed and the sky assumes some longer wave-length color. Finally, when the particles are large enough to reflect as mirrors the sky becomes whitish. Hence both the morning and the evening twilight sky often shows a series of colors ranging from red, near the horizon, through orange and yellow to a green or even blue-green with increase of elevation

and consequent decrease in the number and size of dust particles along the path of light from the sun to that part of the sky in question and thence to the observer.

When the air is filled with fog, or other particles of similar size, the whole sky becomes uniformly gray. This is because the water droplets that together make fog and cloud; though usually so small that it would take from 2,000 to 3,000 of them to make a row an inch long, nevertheless are large enough to reflect, as would little mirrors, and to refract, or transmit in a new direction, light of every color.

It remains now, in preparing the way to an understanding of the weather significance of morning and evening colors, briefly to outline the essential conditions and processes of cloud formation and rain.

Probably that one of these conditions with which the general public is least familiar is the presence, in large numbers, of some sort of nuclei about which water vapor can condense. We can safely assume, too, that in the open atmosphere these nuclei consist only of dust particles, though it is possible in the laboratory, under conditions that rarely, if ever^ exist naturally, to obtain condensation without the aid of dust of any kind.

Besides the presence of dust particles, a certain relation between temperature and water content of the atmosphere is also essential to condensation. The warmer the air, so long as the temperature is below the boiling point, the greater, and, for ordinary temperatures, at a rapidly increasing rate, the amount of water vapor it can contain in the form of a transparent gas.

In reality the relation above discussed is between the temperature and amount of moisture per unit volume, a quantity which does not appreciably change with the presence or absence of other gases. But it is allowable, because of this constancy, to use the popular, though unscientific, expression, “water content of the atmosphere,” provided one thinks of the atmosphere as a mixture of gases (chiefly nitrogen and oxygen) co-existing with the undisturbed water vapor, and not as a sort of sponge that mechanically holds it in suspension.

If, then, air, which always has dust particles in it, containing all or nearly all the water vapor it can hold, is cooled to a dis-

tinctly lower temperature, a corresponding amount of condensation will take place on each dust mote, and the countless droplets thus formed will appear as a fog or cloud of greater or less density.

The most efficient method of producing the cooling necessary to cloud formation is to move the moist air to a place of lower pressure, that is, lift it to a greater elevation, where it will expand and thereby do work against the surrounding decreased pressure at the expense of the heat energy it contains. This effect is well illustrated by the formation of cumuli, or thunderhead clouds, in the summer time; the process of which, in general, is as follows: The earth is heated by sunshine and it in turn heats and expands the adjacent atmosphere and thereby renders it lighter, volume for volume, than the surrounding cooler air. The light, warm atmosphere often nearly saturated with water evaporated from lakes, from moist earth and growing vegetation, and by this vapor rendered still lighter, is buoyed up by cooler and heavier adjacent air, very much as a cork is made to bob up when let go beneath a water surface. The lifted, or, as we commonly say, the rising air, sustains at any particular time only the weight of the atmosphere that is at that moment above it. But, clearly, so long as the air is rising this weight is growing less, and therefore as it passes from a region of greater to one of less pressure it expands just as a compressed spring does when its load is decreased. However, as the spring expands it must do the work of lifting the remaining weight, and so it is with the atmosphere; in expanding it has to lift the air that is above it and thereby do work. Now this work is possible only because of the heat of the active air itself, and consequently as it expands it correspondingly gets cooler. But, as has already been explained, the amount of water vapor that any given volume can hold in the form of a transparent gas, rapidly decreases as the temperature falls.

A rising mass of air, therefore, cools by virtue of its own work in expanding against pressure, and soon reaches a temperature below which it can not contain, as a gas, all its water-vapor. Hence any further rise and consequent cooling leads to precipitation—a collection of the excess

water vapor in droplets about dust particles—and the formation of clouds.

With the foregoing facts in mind it is easy to understand, in a general way, those actions of nature that give meaning to the sky colors of morning and evening, and in large measure justify the proverbs that for ages have been associated with them. Thus we see that a red evening sky means that nothing more than incipient condensation exists even at the tops of the strongly cooled convection currents that obtained during the heated portion of the afternoon (more than this would produce a gray or even cloudy sky), and that therefore the air contains so little moisture that rain, within the coming twenty-four hours, is improbable.

If the evening sky, not far up, but near the western horizon, is yellow, greenish, or some other short wave-length color, then all the greater is the chance for clear weather, for these colors indicate even less condensation (smaller particles) and therefore a dryer air than does red. Hence we can accept the following lines from Shakespeare as the expression of a general truth:

“The weary sun hath made a golden set, And by the bright track of his fiery car Gives token of a goodly day to-morrow.”

If, however, the evening sky has none of these colors, but is overcast with a uniform gray, then we know that numerous water droplets are present, and that the dust particles, in spite of the heat they absorbed from sunshine, have become loaded with much moisture. Obviously, then, to produce this effect, the atmosphere, at considerable elevations, must be practically saturated, a condition that favors rain and justifies the familiar proverbs:

“If the sun set in gray The next will be a rainy day.”

“If the sun goes pale to bed ’Twill rain to-morrow, it is said.”

The above discussion of color phenomena applies to the evening sky only. It remains to explain the origin of similar morning effects and to point out the differences in the processes by which they are brought about.

A grey morning sky means, just as does a grey evening one, that the atmosphere is filled with water globules which are large enough, and even the smallest of

them are, to refract and specularly reflect light of every color. The difference, then, must be in the processes that lead to the formation of the evening and the morning droplets. And these processes are not the same, for the dust of the day sky is heated by sunshine, as are also, to a greater or less extent, both the air and the earth beneath, while the dust in the night sky, as does everything else that is freely exposed, loses of the heat it possesses and cools through radiation to space. Besides, the atmosphere during the day time, and especially in the afternoon, is cooled by convection, which, as already explained, leads to more or less condensation of moisture on the dust that is present; while at night there is no strong upward movement, there being no surface heating, and consequently but little dynamic cooling of the air. The slight condensation here considered is due by day chiefly to convectional cooling, by night mainly to loss of heat through radiation.

Evidently, then, the grey of the morning sky may often be caused by water droplets that have gathered as so much dew on the dust particles in the air—dew that has collected on them because of the slightly lower temperature they maintain through radiation to space, just as, and for the same reason that it collects on blades of grass and other exposed good radiators. But in order that the marked radiation, essential to the formation of the water droplets, may take place, it is necessary that the atmosphere above them be dry, for water vapor does not allow radiation freely to pass through it. Hence a grey morning sky implies a dry atmosphere above the dew droplets, and, therefore, justifies the expectation of a fair day, or even a clear one, for the droplets themselves to which the grey is due are soon evaporated by the rising sun, and convection, in this case, because it mixes the moist lower with a dry upper air, seldom causes precipitation.

A red morning sky commonly implies that the lower and heavier dust particles have been protected from excessive night radiation by a blanket of overlying moisture, else it would be grey ; and at the same time it also implies the presence, in the lower atmosphere, of sufficient moisture to enlarge the dust particles through incipient condensation, else the sky would

have some shorter wave-length color, such as yellow to green. Hence when the morning sky is red the whole atmosphere, to considerable elevations, is moist, and rain, therefore, probable.

Convection in the main, as we have seen, prepares the way for the phenomena of the evening sky, and radiation for those of the morning sky. Hence the amount and distribution of moisture most favorable to any given sky color, such as a grey or red, are radically different in the two cases. There is, therefore, a real physical basis for, and much truth in, the proverbs that declare one result to follow the red of morning and quite another that of evening. There is also justification for some proverbs, two of which have already

been given, that refer to or include other colors.

Additional good examples of the latter are as follows:

“Evening grey and morning red Make the shepherd hang his head.”

“An evening grey and a morning red Will send the shepherd wet to bed.”

“Evening red and morning grey Two sure signs of one fine day.”

“Evening red and morning grey Help the traveler on his way; Evening grey and morning red Bring down rain upon his head.”

^jjgjjHO says, “I fear not,” lies, for all men have fear in their hearts. ^J£HE works of all men crumble and only thought is immortal.

EEK a man for policy, a woman for compromise and a child for truth.

^NOWLEDGE breeds doubt.