The perfect barometer: the historical shift from sensory weather wisdom to scientific meteorology

“ A man may believe it will rain to-morrow because he has consulted the barometer; but if he has no conception how the height of the mercury column (or the position of an index moved by its rise and fall) is connected with variations of atmospheric pressure, and how these in turn are connected with the amount of moisture in the air, his belief in the likelihood of rain is purely empirical. When men lived in the open and got their living by hunting, fishing, or pasturing flocks, the detection of the signs and indications of weather changes was a matter of great importance. ”

“ They survive because they are true. Mariners at sea and shepherds on land learned their lessons well; neither the one nor the other was possessed of a daily weather map. The wind was a fair barometer; the blinking of the stars was an excellent hygrometer. The discovery of the underlying principles of barometric pressure was the beginning of modern meteorology. The use of the barometer quickly appealed to sailors, and practically every deep-water vessel in the world is equipped with one. Transportation companies, lighting companies, farmers and manufacturers find it a necessity. ”

“ He can always tell with the nicest accuracy the point from which the wind blows, and predict with a degree of certainty we never saw excelled, the probable steadiness of the weather, or any approaching change likely to take place in it. He is a perfect barometer in this way, for his conclusions are chiefly drawn from a delicate perception of the state of the atmospheric air imperceptible to others, and are rarely erroneous. On a fine sunny morning when the lakes are smooth, the mountains clear, and the sky without a cloud, we remark to him that it is a fine morning. ”

“ Atmospheric pressure is one of the most basic elements of a meteorological observation. When the pressure at each station is plotted on a synoptic chart, lines of equal atmospheric pressure, called isobars, indicate the areas of high and low pressure. These are useful in making weather predictions, because certain types of weather are characteristic of each type of area, and the wind patterns over large areas can be deduced from the isobars.
Atmospheric pressure is measured with a barometer. The earliest known barometer was the mercurial barometer, invented by Evangelista Torricelli in 1643. ”

“ Thus, before meteorology passed from an “art” to “science,” many individuals learned to interpret certain atmospheric phenomena in terms of future weather, and to make reasonably accurate forecasts for short periods into the future.
With the establishment of weather observation stations, continuous and accurate weather information became available. As observations expanded and communication techniques improved, knowledge of simultaneous conditions over wider areas became available. This made possible the collection of “synoptic” reports at civilian and military forecast centers. ”

“ Throughout Christendom, the prevalence of the conviction that meteorology is obedient to laws, is more and more evident. In cities especially, where men are accustomed each day to see posted in public places charts which show the storms moving over various parts of the country, and to read in the morning papers scientific prophecies as to the weather, the old view can hardly be very influential. ”

“ Meteorology is essentially an international science. The atmosphere knows no political boundaries, and the more it is studied the more strongly meteorologists are impressed with the fact that intimate relations exist between the atmospheric events of widely separated regions of the world. Thus, the great anticyclone that is built up every year over the cold interior of Siberia exercises an influence upon the weather of the United States; the behavior of the Indian monsoons has been found to have some connection with barometric conditions in South America ”

“ Happily, our meteorologists are at length beginning to define with growing clearness and confidence the laws which underlie and regulate the complicated and ever varying phenomena which we call the weather, and many of these laws, like most natural laws, are beautiful in their simplicity. Although ‘weather wisdom’ is as old as history itself, the science of the weather or meteorology is a growth of the last few years. The weather wisdom of our forefathers may in the light of present knowledge be divided into sense and nonsense. ”

“ On such a day the ground hog ventures from his burrow, some restless bee is lured from the hive to wander disconsolate over bare fields, a snake crawls from its hole to bask awhile in the sunshine, and one looks instinctively for the first breaking of the earth that tells of the early crocus and the peeping forth of daffodils. The southerly wind is more apt than not to be a telltale, for with all its springtime softness it is drawing toward some storm center, near or remote, that will inevitably follow with rough weather in its sweep. ”

“ This is because the ground-hog is supposed to be absurdly afraid of his shadow, which he has not seen for so long, and if the bright sunshine reveals it to him he is said to return ignominiously to his hole, where he will remain for another six weeks. ”

“ All weather-wisdom depends upon the principle that Nature never gives false signals, that her laws are invariably true; we cannot interpret them, or we interpret them wrongly. Averages, statistics, observation, instruments, &c., are all helps to a surer interpretation. In proportion as our knowledge of Nature increases, and our instruments are better understood, so will meteorology extend her sway. Thus it has been proposed to give storm warnings to ships in the offing by means of coloured lights. ”

“ The sky was laid bare, as the tidal wave empties the shore of its water before it heaps it up upon it. A violent storm of wind and rain the next day followed this delusive brightness. So the weather, like human nature, may be suspiciously transparent. A saintly day may undo you. A few clouds do not mean rain; but when there are absolutely none, when even the haze and filmy vapors are suppressed or held back, then beware.
Then the weather-wise know there are two kinds of clouds, rain-clouds and wind-clouds, and that the latter are always the most portentous. In summer they are black as night ”

“ Howard attributes these peculiar phenomena to the “sounding board,” made by the stratum of cloud; but sounds may be heard from the north-west, when there is no condensation, and the wind is from that quarter, and also from the east [Pg 392] when it is not cloudy; and in a level country the village bells often tell the direction of the current of air just over our heads when we do not feel it at the surface. The wind is undoubtedly moving in a rapid, and perhaps invisible current, not far above us. If from the east or south, it betokens rain; if from the western quarter, fair weather. ”

“ It may be rash to say that meteorological science can gain nothing from scientific observation of animal life; but the character of the weather-lore that has been handed down from father to son for the past two centuries plainly indicates that the observations which gave rise to them were anything but scientific in character. Mankind now, as formerly, may be close observers of Nature, but this does not imply that they are accurate observers. ”

“ This pressure varies according to the state of the weather, and the changes are indicated by an instrument called a barometer. Generally speaking, the falling of the mercury in the tube of the barometer indicates rain, and its rise heralds clear weather. Sometimes the rise is followed by cold winds, frost and ice. What these changes really indicate, however, can be determined only by comparing the barometric changes, at certain hours, in a number of places very far apart. This is done by the Signal Service. ”

“ Of these local observations, the pressure readings are by far the most important. A falling barometer usually means the approach of a cyclone, with wind, or storm, or both. A rising111 barometer, on the other hand, is usually an indication of the fine weather associated with an anticyclone. The unsymmetrical distribution of weather, characteristic of our cyclones in the United States, and also of most cyclones in the Temperate Zone, is associated with their unsymmetrical form, and the unsymmetrical distribution of their temperature already studied. ”

“ The cooling effect produced by a draught does not necessarily arise from the wind being cooler, for it may be actually warmer, but arises from the rapid evaporation it causes on the surface of the skin. Vapor of water forms a blanket about the earth and prevents it from scorching during the day and freezing during the night.
How to Forecast Weather with Only an Aneroid Barometer. No one except an expert observer should use the mercurial barometer. The aneroid will answer as well for the purpose of forecasting from a single instrument; it is cheaper and less complicated. ”

“ THE science of the weather may be said to have sprung up within the last half century, and we must not therefore wonder that, until very recently, meteorological science has rather been concerned with the weather as it has been, than in prophesying what kind of weather may be expected. Indeed, this is almost the case at the present day; for, were it not for the telegraph, storm-signals would be of little avail. Much was gained when, from the conclusions drawn from a large number of observations, a storm could be telegraphed from any place as coming, instead of as happened. ”

“ They have found that there is a sort of advance guard of rain, behind which is the lowest barometric area; and they regard that part of the country where the barometer is lowest as the centre of the storm. The reports from various stations show the path of the advancing rain, and the weather observers know that a low barometer is likely to follow it. They cannot tell exactly how fast it will advance, for areas [Pg 484] of clear weather stand in the way of the storm, and local causes sometimes prevent them from yielding quickly. ”

“ The fact that our northeast storms come from the southwest, which was first noticed by Benjamin Franklin some years before he put the suggestion just quoted in writing, was one of the great contributions to meteorology made by Americans. Modern weather forecasting essentially depends upon the general eastward movement of cyclones and anticyclones, with their accompanying weather conditions.
The daily weather map shows us the actual condition of the weather all over the United States at 8 A.M., “Eastern Standard Time.” The positions of cyclones and of anticyclones ”

“ It will greatly enrich the meteorology of the ocean and aid navigation, by supplying data for deducing those true mean physical values which teach the mariner at sea where he may find "a fair wind and a favorable current," how he may best utilize the forces of nature and elude its terrors. It will afford material for the renovation of the climatology and sanitary meteorology of regions not now fully investigated. But, above all, it will facilitate the elucidation of the laws of storms and those associate phenomena which conspire to produce the many-colored phases of "the weather." ”

“ Some people are disposed to laugh at the forecasts made, but in the main they are very trustworthy.
Rain gauges and solar thermometers, Kew.
It is never possible to be quite sure what will happen at any one spot, but over a district the readings of the barometer afford the practised meteorologist a fairly accurate idea of what is coming, and it is worthy of note that the failures, or partial failures, in the prophecies during a year are considerably less than 20 per cent. On the coast the prognostications of the Meteorological Office have been of immense service. ”

“ Researches are now being carried on which tend to show that the meteorology of the two hemispheres is more interdependent than was hitherto believed, so that a meteorological disturbance in one part of the world makes its presence felt, more or less remotely perhaps, all over the world. ”

“ It is believed that a further discussion of meteorological phenomena on a broad basis, by means of International Weather Charts, both in daily and monthly form, must eventually result in important and fundamental discoveries. It is gratifying to American pride to know that in this international task of outlining the geography of the air, the United States has liberally provided the labor and means for presenting these ten years' meteorological data in such tabular and geographical forms as to render them available for study by all. ”

“ No bad weather ever comes on our coasts without timely warning being given by the barometer. The oldest seaman are often deceived by the look of the weather, but there is no instance on record of very bad weather, such as would have involved loss of life to the extent we have heard of in several years, having come on without the barometer having given timely warning. ”

“ As mankind are always desirous of attaining weather wisdom, these rules have tended to give the barometer its widely recognized reputation, rather than any really infallible principles, clearly formulated. With no other philosophical instrument have people so deluded themselves as with the barometer. Meteorology having become almost an official monopoly, the officials seem to have made the readiest and largest amount of reputation out of the barometer as a weather glass ”

“ I do think that, of all the silly, irritating tomfoolishness by which we are plagued, this “weather-forecast” fraud is about the most aggravating. It “forecasts” precisely what happened yesterday or a the day before, and precisely the opposite of what is going to happen to-day. ”

“ Still, infallibility can not be expected, however favorable the locality. "It is impossible to suppose," says the author, "that we have yet nearly reached the highest perfection of which forecasting is capable, but still we know enough of the nature of the subject to say with certainty that calculation will never enter much into the science of weather-prevision. Natural aptitude and the experience of many years' study are the qualifications of a successful forecaster. In fact, meteorology is not an exact but an observational science, like geology or medicine." ”

“ The disturbances in the general circulation which are produced by the land and ocean areas make it well-nigh impossible to reduce meteorology to any simple scientific system. The irregularities produced by the interaction of these warm and cold masses are so great that the problem of forecasting seems to bid defiance to any clear classification. ”

“ But in certain cases it has been found permissible to neglect a number of influences owing to their minuteness, and science has thus been able to progress. It is because in meteorology this restriction of active influences to a minimum appears impossible that long-range weather prediction is any man’s guess. ”

“ Barometer and Wind Indications.—When pressure and wind-direction are both considered and interpreted according to their mutual relations, local forecasts can be made with a much greater degree of certainty. During the colder months, throughout the United States, the western highlands excepted, precipitation begins with falling pressure. In the summer months, and in the western highlands it is apt to begin with the rising barometer. ”

“ A man who possesses a barometer and a thermometer, and knows how to read them, can beat all prophets out of the field. Change of weather is gradual, and great storms or changes are usually shown by falls of the barometer exceeding an inch, and by differences of temperature exceeding fifteen degrees. The more rapidly such changes occur, the more risk is there of severe weather. The normal height of the barometer in these latitudes is 29.24 to 30.00, though 27.45 has been registered in the Orkneys. A tenth of an inch an hour is a fall indicating a storm or very heavy rain. ”