From the foregoing outline it will be seen that a bewildering variety of climatic statistics may be computed merely from observations of temperature, and the same is true of the other elements. Moreover, the list set forth above is by no means exhaustive even for temperature. In fact, there is almost no limit to the number of ways in which the raw material of climatic data—i. e., the original records of observation—may be grouped, averaged, or otherwise treated in order to bring out certain features of the climate that may conceivably serve some useful purpose. The reader will now be able to understand why a treatise on the climate of a single locality often fills a substantial volume.
The numerical data contained in such a work are generally supplemented by text descriptions and by various graphic devices, such as curves showing the normal fluctuation or “march” of a weather element during a day, year, or other interval. Workswhich deal with the climates of larger areas, such as whole countries, are usually accompanied by climatic charts. These charts furnish a quick and easy way of getting a general idea of the climate of a region. Among the more important climatic charts are the following:
1.Temperature (isothermal) charts.These include charts showing the distribution of normal temperatures for months, seasons, and the year; normal range of temperature for similar periods; highest and lowest temperatures ever recorded at the different stations; etc. Lines known asisothermsare so drawn as to pass through places having identical values of the element in question (mean temperature, highest temperature, etc.).
2.Rainfall (isohyetal) charts.These show the distribution of rainfall (including snowfall, expressed in equivalent depth of water); especially for each month and for the year. Other charts may show the average number of rainy days; average snowfall (actual depth, not water equivalent); seasonal distribution of rainfall; etc.
3.Wind charts.These are drawn in various forms, to show the prevailing wind directions, the frequency of winds from different directions, the average force of the winds, etc. Charts of the winds at different levels above the earth’s surface will eventually be drawn for the use of aeronauts, but such charts are still in a tentative stage.
A MODERN ISOTHERMAL CHART OF THE GLOBE. (Hann, 1901)The isotherms show the mean annual temperature in centigrade degrees.
A MODERN ISOTHERMAL CHART OF THE GLOBE. (Hann, 1901)The isotherms show the mean annual temperature in centigrade degrees.
As in the case of tabulated climatic data, the number of charts that might be drawn to bring out different features of climate is practically unlimited. Sunshine, cloudiness, humidity, barometric pressure, and the frequency of various special phenomena, such as thunderstorms, hail, tornadoes, droughts,etc., are all charted in some of the more extensive works on climate. Large atlases have been published to portray the climates of certain countries. The study of the actual distribution of climates over the earth, as distinguished from that of climate in general, is sometimes calledclimatography.
Climates are variously classified, usually on the basis of one or more of the climatic elements, but sometimes with reference to their effects. The most familiar classifications refer to temperature. We speak of tropical, temperate, and polar climates; but in using these terms it should not be forgotten that other things besides latitude control the distribution of temperature. Location with respect to the ocean or other large bodies of water is almost equally important. A land surface grows warm by day and in summer, and grows cold by night and in winter, much more rapidly than a water surface, and the adjacent air varies in temperature accordingly. Hence we have a classification of climates asmarineandcontinental. The former, under the influence of oceanic winds, have a moderate range of temperature, while the latter are subject to extremes of heat and cold. With increase of altitude temperature is diminished, but rainfall is generally increased. The distribution of rainfall is also determined to a great extent by the paths of cyclonic storms. Such are a few of the many things that control the complex distribution of climates.
People who never travel far from their own homes usually cherish quite erroneous ideas regarding the climates of distant lands. It is hard for most Americans to realize, for example, that the Isthmus of Panama, in the heart of the tropics, never experiences temperatures nearly so high as those whichoccur every summer in the United States. A citizen of South Dakota, where the mercury, in the shade, frequently rises above 100° Fahr., and has been known to reach 115°, will be inclined to revise his definition of the term “tropical” when he learns that at Colon, the Atlantic terminus of the Canal, a temperature as high as 90° is decidedly exceptional, and that the maximum reading during a period of six years was only 92°. In thirteen years Canal Zone vital statistics showed only two deaths from sunstroke and twenty-one non-fatal cases of heat prostration among a population of 120,000. It will also surprise most Americans to learn that the highest natural air temperatures that have been recorded anywhere on earth were not observed near the equator, but in a California desert. At a place on the edge of Death Valley, rejoicing in the ironical name of Greenland Ranch, a temperature of 134° Fahr. was registered in July, 1913. The thermometer which furnished this remarkable reading was a tested instrument, installed in a standard screen over an alfalfa sod, and not exposed to the reflected heat of the desert. At the same place the temperature reached 100° or more on 548 days in four years. Outside of the United States the highest temperature ever recorded at a meteorological station was 127° Fahr. at Wargla (Ouargla), Algeria.
The lowest temperatures encountered by polar explorers are considerably higher than those experienced each winter by the inhabitants of northern Siberia. The “record,” so far as instrumental observations go, is held by the town of Verkhoyansk, at which the temperature fell to 90° below zero (Fahrenheit) in February, 1892. Strange to say,this “winter cold pole” of the earth has warm summers. At Verkhoyansk the temperature sometimes rises to 80° above zero, or higher. At Yakutsk, Siberia, the thermometer has been known to fall to 84° below zero in winter and to rise 102° above zero in summer; a range of temperature exceeding the interval between the freezing point and the boiling point of water!
Another climatic paradox is that experienced by mountaineers who, in scaling peaks mantled in eternal snow, often suffer with the heat, on account of the intensity of solar radiation in the pure, dry air of high altitudes. At the health resort of Davos, in the high Alps (altitude 5,250 feet), invalids sit out-of-doors without wraps in midwinter, and, indeed, are sometimes driven into the shade to escape the too ardent rays of the sun. At the same time the temperature of the air itself may be far below freezing, and the ground covered with snow.
Certain parts of the world are often loosely described as “rainless,” but, as we have stated elsewhere, there is actually no spot on earth at which rain (or snow, in the polar regions) has never been known to fall. In the driest part of the Sahara—the Libyan Desert, between Dakhel and Kufra—the explorer Rohlfs experienced a drenching rainstorm of three days’ duration in 1874. Neither is the Sahara, in spite of its proverbial heat, exempt from touches of real winter. Snow is a common occurrence in many parts of this desert, even at moderate altitudes. On the higher Saharan peaks snow lies on the ground all winter, and is sometimes found, in sheltered spots, in summer. Occasional falls of snow occur in all parts of Algeria, and several falls have been recorded in Lower Egypt.
When all is said and done, the whole fabric of what now constitutes the science of climatology leaves much to be desired. Climate is of practical interest, first of all, on account of its effects on human life and health, and secondly because of its influence upon the crops that are the mainstay of man’s material prosperity. Under both these heads climatic data, as now commonly presented, ignore certain atmospheric activities of the utmost importance. For biological purposes no description of a climate can be regarded as even approximately complete that does not furnish, for the region under discussion, a detailed account of the different kinds of radiation received from the sun, their intensities and fluctuations; and there are few places in the world at which even a beginning has been made in the collection of such data. Again, the phenomena of atmospheric electricity, including radioactivity, are probably of real climatic significance, but we are still in the stage of speculation with regard to this subject. Possibly there are still other elements of climate, now wholly neglected, that will figure prominently in the climatology of the future.
Noother branch of science is so dependent upon the constant systematic cooperation of a multitude of workers as meteorology. There are, to be sure, some kinds of atmospheric phenomena that can be studied advantageously by the individual meteorologist, with no further aid from his scientific confrères than the same sort of interchange of ideas that prevails in all departments of knowledge; but the widespread processes that constitute weather and climate require for their observation—whether the purpose in view be weather forecasting, or the collection of climatic statistics, or the assembling of data from which to deduce the laws of atmospheric movements—a veritable army of colaborers, equipped with standardized instruments and keeping their records according to a uniform plan.
Probably few people, in looking at the charts portraying the climates of the world that are found in reference books, realize how many observers have contributed to the preparation of such charts or the number of separate instrumental observations upon which they are based. In the United States alone there are something like 6,000 meteorological stations, at which upward of two and a quarter million observations are made every year—and a climatic chart is, of course, the fruit ofmanyyears of observations. At the beginning of the present centuryit was estimated that there were 31,000 meteorological stations in operation throughout the world. The present number is doubtless much greater. At some of these stations observations have been made regularly, once, twice or three times a day, for 100 or 150 years. In round numbers one may say that, during the last few decades, meteorological observations have been made, the world over, at the rate of ten million a year, and the total number, since the keeping of regular weather records began, runs far up in the hundred millions.
Organized meteorological observations were not unknown to antiquity—we have mentioned elsewhere the early rainfall measurements in India and Palestine—but the present era of such undertakings dates back only to the middle of the seventeenth century. In the year 1654 the Grand Duke Ferdinand II of Tuscany, through his chaplain and secretary, Luigi Antinori, secured the cooperation of several observers in Italy and the adjacent countries, to whom were distributed instruments and forms for maintaining daily records of the principal meteorological elements. Antinori and most of the observers belonged to the Jesuits, an order which has displayed extraordinary zeal in the furtherance of meteorology down to the present day. The observations thus inaugurated appear to have been kept up until about 1667, but unfortunately few of the records have been preserved. Several undertakings of similar character were launched during the next hundred years in France, England, and Germany. The most notable of such enterprises, however, antedating the foundation of the present official weather services, was the international system of observations maintained by the Meteorological Society of thePalatinate, founded at Mannheim in 1780 under the auspices of the Elector Karl Theodor. The chief credit for the epoch-making work of this society is due to its secretary, J. J. Hemmer. The society distributed standard instruments to its observers, who were widely scattered over the world; viz., fourteen in Germany, two in Austria-Hungary, two in Switzerland, four in Italy, three in France, four in Belgium and Holland, three in Russia, four in Scandinavia, one in Greenland, and two in North America (at Bradford and Cambridge, Mass.). The very detailed observations of this network of stations down to the year 1792 were published in twelve large volumes.
Although the activities of the Mannheim society came to an end in the troublous days of the French Revolution, the records that it had collected served as the groundwork for fruitful studies during the next generation. There are two distinct uses that can be made of statistics of this sort. First, they can be digested in such a way as to bring out the characteristic features of the climate at each of the localities included in the collection, and likewise to illustrate the distribution of climates over the globe. Second, the data for individual days from the various stations can be charted separately, so as to illustrate theinstantaneousdistribution of barometric pressure, wind and weather, and, by a comparison of the charts for successive days, to provide a sort of moving picture of the atmospheric machinery in operation.
Charts based on approximately simultaneous observations showing the state of the atmosphere at a particular moment of time over an extensive area of the earth are calledsynchronous charts, or sometimessynoptic charts, though the latter term is also applicable to charts showing average values for a particular month, year, etc. Synchronous charts, as used nowadays for the purpose of making forecasts, are prepared from data collected by telegraph; but the same kind of charts can be prepared in a more leisurely manner from the statistics gathered at any previous time, and such charts were frequently made for the purpose of study before the days of telegraphy. The pioneer in such undertakings was the German physicist, H. W. Brandes, who, about 1820, utilized the observations collected by the Meteorological Society of the Palatinate, together with some others, in compiling a series of daily synchronous charts of Europe for the year 1783.
Very similar studies were carried out in America, a few years later, by J. P. Espy, W. C. Redfield and Elias Loomis. Early in the nineteenth century a copious fund of meteorological observations had already accumulated in this country. The first undertaking in the nature of a meteorological organization, foreshadowing the present Weather Bureau, was due to Josiah Meigs, Commissioner of the General Land Office, who in 1817 established a system of tri-daily observations at the various land offices. At an almost equally early period the Surgeon General of the Army inaugurated regular weather observations at the military posts throughout the country. Local systems of observations were established by the authorities of New York State in 1825 and Pennsylvania in 1837, and systems of broader scope by the Patent Office in 1841 and the Smithsonian Institution in 1847. Experiments in collecting weather reports by telegraph for the purpose of forecasting storms were undertaken by the SmithsonianInstitution as early as 1849. At about the same period Lieut. M. F. Maury, of the navy, was gathering meteorological reports from mariners and laying the foundations of marine meteorology. Finally, in 1870, Congress was induced to establish a full-fledged telegraphic weather service, similar to those that were already in successful operation in Europe. One of the great promoters of this enterprise was Dr. I. A. Lapham of Wisconsin; it had been repeatedly advocated by Maury; and a convincing object lesson in its behalf was furnished by the local service of reports and forecasts conducted by Prof. Cleveland Abbe, at the Cincinnati Observatory, with the aid of the Western Union Telegraph Company, in 1869 and 1870. During the first twenty years of its existence, from 1870 to 1890, the Federal weather service was under the Signal Corps of the army. Since 1890 it has been a branch of the Department of Agriculture, as the United States Weather Bureau, though the name “Signal Service” stuck to it, in popular speech, long after it ceased to belong to the army.
In this country weather forecasts are—or once were—said to emanate from “Old Probabilities,” or “Old Probs.” Our first “Old Probs” appears to have been Professor Abbe, who has explained the origin of this name in an account of his pioneer forecasting experiments at Cincinnati. He says of the initial Cincinnati Weather Bulletin, issued September 1, 1869:
“It contained only a few observations telegraphed from distant observers and announced ‘probabilities’ for the next day. This bulletin, in my own hand-writing, was posted prominently in the hall of the Chamber of Commerce, but unfortunately I had misspelled‘Tuesday,’ and I soon found below my Probabilities the following humorous line by Mr. Davis, the well-known packer: ‘A bad spell of weather for “Old Probs.”’ This established my future very popular name of ‘Old Probs.’” The name has, however, been more particularly associated with Gen. Albert J. Myer, who, as Chief Signal Officer, was the first head of the Federal meteorological service.
Desultory experiments in the collection of current weather reports and their use in constructing weather maps were first carried out in Europe at about the same time as the early undertakings of this character in America. Such reports were gathered and published by James Glaisher, with the cooperation of the British railways, in 1849. The existing national weather services of the Old World owe their origin to an episode of the Crimean War. In November, 1854, a violent storm wrought havoc among the French and British warships in the Black Sea and sank many vessels containing invaluable stores intended for the Allied armies in the Crimea. The French astronomer Le Verrier, director of the Observatory of Paris, collected information showing the progress of this storm across Europe, and the results of this inquiry were so significant that he submitted to the Emperor Napoleon III the plan of organizing an international system of telegraphic reports, by means of which timely warning could be obtained of similar atmospheric disturbances. The French Government, with the aid of other European countries, established such a system in 1855. Within the next two decades most of these countries organized their own services, and at the same time maintained an international exchange of observationsby telegraph. Before the close of the nineteenth century nearly all the civilized countries of the world, including many colonial possessions, such as Canada, Australia, Algeria and the Philippines, had established meteorological services, entailing more or less extensive arrangements for collecting daily reports by telegraph and issuing storm warnings and weather forecasts. The chief exceptions were several of the Latin-American republics and the Ottoman Empire, in which such organizations are still lacking.
Meteorology is essentially aninternationalscience. 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; and fluctuations in the force of the trade winds are apparently of world-wide significance—whence these winds have been described as the “pulse” of the general atmospheric circulation. The French meteorologist L. Teisserenc de Bort called attention many years ago to the existence of what he called “centers of action”; viz., large permanent or semi-permanent areas of high and low barometric pressure, the variations of which correspond strikingly with the vicissitudes of wind and weather in countries thousands of miles distant. Last but not least, persistent attempts have been made to interpret all the weather happenings on our globe in terms of afluctuating supply of radiant energy received from the sun.
Fortunately meteorology has possessed an international organization for a great many years. The International Meteorological Organization was founded at a conference held at Leipzig in 1872, and was perfected at a formal congress of meteorologists convoked at Vienna in the following year. The International Meteorological Committee, which is the permanent working body of the organization, was established at the Vienna Congress. Finally, the organization was reconstituted at a conference held at Paris, by invitation of the French Government, in 1919.
The International Committee consists of not more than twenty members, all of whom are directors of official meteorological services. It is supposed to meet at least once in three years. At less frequent intervals are held “conferences,” to which are invited representatives of all the meteorological services and the principal independent meteorological observatories of the world. Attached to the organization are several international “commissions,” which supervise and coordinate the work of meteorologists in various special fields. At the close of the year 1921 there were commissions on the following subjects:
Agricultural Meteorology, Weather Telegraphy, Marine Meteorology, Solar Radiation, Application of Meteorology to Aerial Navigation, Réseau Mondial, and Polar Meteorology, Investigation of the Upper Air, Terrestrial Magnetism and Atmospheric Electricity, Study of Clouds.
Each commission includes in its membership at least one member of the International Committee,besides a number of experts, from different countries, in the particular subject with which the commission is concerned.
The resolutions adopted at the various international meetings of meteorologists have been collected in the “International Meteorological Codex,” the chief object of which is to secure uniformity in methods of observation, forms of publication, etc.
One of the most notable international undertakings in the history of meteorology was the plan of simultaneous observations, at Greenwich noon, both at land stations and on board ships, adopted by the Vienna Congress at the suggestion of General Myer, and carried out under the auspices and mainly at the expense of the United States Signal Service. The results of these daily observations, from 1875 to 1887, were published in detail, with charts, by the Signal Service. The many bulky volumes of this series, illustrating the meteorology of the globe (or mainly the northern hemisphere) day by day for a period of more than a decade, are the modern analogue of the “Ephemerides” issued a century earlier by the Meteorological Society of the Palatinate—which cover very nearly the same length of time. In recent years the efforts of meteorologists have been bent toward establishing a so-called “réseau mondial,” or world-wide network of stations, which will not only provide telegraphic reports for the use of forecasters, but will also send their detailed records to an international commission to be compiled and published. The telegraphic feature of this project now bids fair to be realized in a manner that was not contemplated when the plan was originally proposed; viz., by the broadcastingof weather reports from high-powered radio stations all over the world.
An effective “world weather bureau,” with permanent headquarters and staff, is at present the most urgent desideratum of practical meteorology. Such a bureau would not only tie together the national weather services of the world and greatly facilitate their operations, but would also digest the great mass of existing climatic statistics and provide for extending the climatological survey of the globe to regions where meteorological stations are scarce or lacking.
A typical national meteorological service comprises a central station or institute, usually, but not always, situated at the national capital, and a network or “réseau” of subordinate stations, which are sometimes classified, according to the extent of their observations, as stations of the first, second, and third order. They may also be classified, from another point of view, as telegraphic and nontelegraphic stations. The former provide telegraphic reports of their observations, which serve as the foundation for forecasts, while the latter are maintained chiefly for the purposes of climatology. In some countries—notably in the United States—there are additional classes of stations engaged in particular lines of work; these include storm-warning stations, river stations (which report river stages and rainfall in the river basins), stations for agricultural meteorology, etc. Several of the great maritime nations collect reports from vessels on the high seas, including a small percentage of wireless reports. A number of the national meteorological services carry on work in other branches of geophysics, such as seismology and terrestrial magnetism.
The United States Weather Bureau is an exception to the rule that, apart from the central offices and a few special stations and large observatories, meteorological stations are not generally manned by professional meteorologists, nor are the observers paid specifically for their meteorological work, though in a great many cases they are public functionaries who are expected to take meteorological observations in addition to their other duties. In this country there are about 200 stations at which the observers, of whom there are from one to a dozen or more at each station, devote all their time to the work of the stations and are salaried employees of the Weather Bureau, and there are several hundred minor stations manned by part-time paid employees. But even in the United States the great majority of the meteorological stations are operated by unpaid observers. There are about 4,500 of these so-called “cooperative stations,” which provide the bulk of the climatic statistics of the country.
Some of the leading meteorological services of the world, and the places at which their central offices are located, are as follows:
United States Weather Bureau (Washington), Meteorological Service of Canada (Toronto), Meteorological Office (London), Office National Météorologique (Paris), Reale Ufficio Centrale di Meteorologia e Geodinamica (Rome), Zentralanstalt für Meteorologie und Geodynamik (Vienna), Indian Meteorological Department (Simla), Central Meteorological Observatory (Tokyo), Commonwealth Bureau of Meteorology (Melbourne), Oficina Meteorológica Argentina (Buenos Aires).
In Germany there are several mutually independent meteorological establishments, of which the PrussianMeteorological Institute, with headquarters in Berlin, is the most important with respect to climatology and research, while the Deutsche Seewarte, at Hamburg, is the chief center for telegraphic weather reports and issues the principal weather map. Russia, before her debacle, had one of the most splendidly organized meteorological services in the world, with headquarters at the Central Physical Observatory in Petrograd, and a separate service for agricultural meteorology, which was the model institution of its kind. The Philippine Islands have a Weather Bureau which is entirely distinct from that of the United States. This Bureau, with headquarters at the Manila Observatory, was founded by the Jesuits, who also maintain a quasi-official meteorological service in China, with headquarters at the Zikawei Observatory, near Shanghai.
Many meteorological societies have done much for the progress of the science, and in some cases have shared the duties of the official meteorological services, especially in maintaining stations for climatology. These include the Royal Meteorological Society and the former Scottish Meteorological Society, in Great Britain, the French, Italian, German, Austrian, and Japanese meteorological societies, and the American Meteorological Society, which was founded in December, 1919.
“Forecast”—with the stress on the first syllable when it is a noun, but often on the second when it is a verb—is a word that meteorology has made peculiarly its own. This fact is not the result of accident, but of design.
The founder of scientific weather prediction in Great Britain was Admiral Robert FitzRoy—the same talented officer who explored the coasts of South America in theBeagleand had Darwin for a fellow-voyager—and his first predictions were issued in 1861 from the Meteorological Department of the Board of Trade, which was under his charge. The boldness of this pioneer undertaking is not easily realized by the present generation, which is accustomed to see the official weather forecast at the head of every daily newspaper. Weather prognostication had previously been the undisputed province of charlatans and quacks. For a civilized government to embark upon such an enterprise must have seemed, to the educated public, very much like charging the Astronomer Royal with the duty of casting horoscopes.
A GLASS WEATHER MAP OF THE UNITED STATES WEATHER BUREAU(Courtesy of U. S. Weather Bureau.)
A GLASS WEATHER MAP OF THE UNITED STATES WEATHER BUREAU(Courtesy of U. S. Weather Bureau.)
A GLASS WEATHER MAP OF THE UNITED STATES WEATHER BUREAU
(Courtesy of U. S. Weather Bureau.)
There is much virtue in a name. A few years ago the United States Bureau of Fisheries persuaded the American public to eat dogfish by changing its name to “grayfish.” Similarly, FitzRoy induced the British public to take his weatherpredictions seriously by calling them “forecasts.” The name has stuck; and nowadays, throughout the English-speaking world, the expression “weather forecast”—except as applied comprehensively to predictions of the “long-range” variety—means something decidedly less chimerical than the average weather prophecy.
THE SUN DRAWING WATER(Photograph by P. K. Budlong.)
THE SUN DRAWING WATER(Photograph by P. K. Budlong.)
THE SUN DRAWING WATER
(Photograph by P. K. Budlong.)
It is still necessary, however, to emphasize the distinction. There are probably many people among us, well above the illiterate level, who have no clear idea as to what constitutes a scientific weather forecast. The distinguishing feature of such a prediction, apart from the fact that it is made by a trained meteorologist, is that it is, in all cases, based upon a weather map.
The forecasting machine is a big one, with its human gear spread over a wide territory. Eventually it will be spread over the entire globe, and then we shall have better forecasts. A little manual entitled “The Weather Map,” published by the British Meteorological Office, says:
“The making of a single forecast in any one of the meteorological offices of Europe, America, Australia, or the Far East requires the organized cooperation of some hundreds of persons; about a hundred observers who note the necessary observations simultaneously at as many separate places and hand in their reports to the telegraphists who transmit them to one center, where the meteorological expert charts them on a map and draws therefrom the conclusions on which the forecasts are based. The preparation of the map is an essential part of the process. No meteorologist in the modern sense attempts to forecast the weather without reference to a map prepared either by himselfor by some one with whom he is in direct communication, from observations transmitted by telegraph for the purpose. No amount of weather wisdom or weather lore or experience is a substitute for the map. The more expert and accomplished the meteorologist, the more certain he is that all he can do without the materials for constructing a map, though he may have a barometer and other instruments at hand, is to make a guess at what the map is like and think out from that what the weather changes are likely to be. It is a common experience of professional meteorologists away from their base to find themselves appealed to for an opinion about the weather, judging from the signs of the sky alone, because they are learned in such things. That is exactly what they are not. Accustomed to refer everything to a map, without one they feel themselves to be rather worse off than those who are unaccustomed to its use. A modern meteorologist thinks in maps; his language and modes of expression are formed thereby.”
While the weather map is prepared, first of all, for the use of the forecaster, who makes his predictions from the map before it has passed beyond the manuscript stage, it has other important uses, which justify its publication and widespread distribution. The weather map is a weather newspaper. Like other newspapers, it is founded on a system of telegraphic dispatches and is designed to keep us in touch with what is going on in the world. Weather news is of general interest because weather plays a part in most of the doings of humanity. Sometimes the news we read on the face of the map merely satisfies our curiosity; at other times it renders us more substantial service.
By way of illustrating the manifold purposes served by weather maps, let us set down two cases that are, perhaps, at opposite ends of the scale of utility. Our first case is that of the traveler who scans the map to see whether the atmospheric conditions at his distant home are propitious, that day, for some outdoor pleasure event on the family program. This we may describe as a sentimental use of the map. The second case is that of an aviator embarking on a flight some time in the fore part of the day, soon after the morning map has made its appearance. Here is a case in which the map is of vital utility, purely as a record of current conditions. The aviator is not concerned with the forecast of the morrow’s weather, unless he is making an unusually long flight, but he is immensely concerned with the winds and weather prevailing along his route at the time he flies, and these will not, as a rule, differ radically from the conditions shown on the map of the same morning.
Since weather affects business in a variety of ways, people who have business interests away from their places of residence frequently have occasion to consult the weather map. The influence of the weather on crops explains why the map is watched with keen interest by dealers in agricultural products. Owners of vessels navigating the ocean or the Great Lakes take a practical interest in the present as well as the future location of storms. And so on. It is not necessary to prolong this list of those who use the weather map, because the popular demand for it speaks for itself. It is worth while to record the fact that the demand far exceeds the supply. In this country the Weather Bureau has been constantly harassed with urgent requests for the publicationof maps at places where, in consequence of limited appropriations, it has not been possible to issue them.
The weather maps published in various parts of the world exhibit much diversity in detail, though they have, of course, many features in common. As a rule a weather map covers a wider area than that of the country in which it is published. The aim has always been to make these publications international, as far as practicable. The longest continuous file of printed daily weather maps in existence, viz., that established in France by Le Verrier in 1863 and still published, has been called from its beginning the “Bulletin International.” It embraces nearly the whole of Europe, a little of Africa, Iceland, and the Azores. The other European maps now cover the same area or a considerable part of it. Before the war the Russian meteorological service was issuing a map that included, in addition to Europe, a wide zone of Asia extending all the way to the Pacific Ocean. The United States map, as published in its most extensive form at Washington, comprises the whole of this country and southern Canada, besides presenting tabulated statistics for more distant parts of the world. Manuscript maps prepared daily at Washington have a still broader outlook; they are drawn on a base map that covers the northern hemisphere, and the printing of a map of this sort, including a chain of stations extending around the globe, was undertaken in 1914, but was interrupted by the war. The map published by the Argentine Meteorological Office, at Buenos Aires, covers more than half of South America. Most national meteorological services issue weather maps, but there are a few that donot. No such maps are published in South Africa or any of the South American countries except Argentina.
LAND AREAS EMBRACED IN DAILY WEATHER MAPS AS PUBLISHED IN 1921
LAND AREAS EMBRACED IN DAILY WEATHER MAPS AS PUBLISHED IN 1921
Thus there is still much room for the horizontal extension of the weather map, and there is even more room for its vertical extension. Daily weather maps for aeronauts (chiefly wind maps) are now more or less on the programme of all the leading meteorological services, and in a few cases their publication has already begun. Probably the first maps of this character, showing the winds at various levels over a whole country, were those that began to appear in Italy in 1913. The British Meteorological Office now publishes such maps, showing winds and clouds at different levels over the British Isles at three hours of the day. In the United States maps of the “wind aloft” are prepared daily, at Washington, from the reports of kite and balloon stations, but they are not yet published. The Weather Bureau has, moreover, invented an ingenious method of depicting the winds at several levels on a single map; in other words, constructing a map in three dimensions. This consists of attaching arrows to little metal posts erected on an ordinary weather map at points corresponding to the location of the upper-air stations. Each post bears a series of arrows—one arrow for each level charted—and the arrows are set in positions showing the direction of the wind at each level. Numbers on the arrowheads indicate the force of the wind. When the map is finished it is photographed from two different angles so as to make a pair of pictures suitable for viewing through a stereoscope. These stereoscopic pictures were formerly made every day and a file of them is available for reference and study.
STEREOSCOPIC MAP OF THE “WINDS ALOFT”(Larger)
STEREOSCOPIC MAP OF THE “WINDS ALOFT”(Larger)
There are a few conspicuous points of difference between the weather maps issued in foreign countries and those issued in this country. Thus a majority of the foreign weather services publish two or more charts on the same sheet; either for the sake of showing different meteorological elements separately or, in most cases, to represent the conditions prevailing not only at the hour of the current morning observation, but also at certain hours of the previous day. One of the three editions of the British map includes four charts, corresponding to observations at four different hours. By means of such series of charts one can observe the recent changes of weather as well as the current conditions. Weather maps published in the United States show primarily the conditions at 8 a. m., Eastern Standard Time, of the morning of issue; though certain features of past weather are also indicated, including changes of temperatures, movements of storm centers, etc. Evening maps are drawn at Washington and at many other places, but are not published.
In this country the publication of weather maps has been carried out on a much more liberal scale than elsewhere. Instead of issuing maps at only one or a few places, as is the custom in other parts of the world, it has been the policy of the American service to publish them at populous centers all over the country. In some cases they are printed or manifolded at the local Weather Bureau station, and distributed by mail and messenger; in other cases they are published in the newspapers. The daily circulation of the maps has thus, at times, run up into the millions. This comprehensive duplication of the chart is made possible by special arrangements with the telegraph companies. The reports of observationsare, to a large extent, sent over circuits, along which the telegraph offices, besides forwarding the local report, copy the reports from other stations as they pass over the wires. Certain stations, forming connecting links between the circuits, effect the transfer of collected reports from one circuit to another; so that, in a very short time, upward of 150 stations receive the reports from a large number of other stations. The maps issued at stations or published in newspapers are generally rather crude, though they answer their purpose; but the large lithographed map issued every day at the Central Office, in Washington, is much the most artistic production of its kind published anywhere in the world.
ENLARGED SECTION OF THE STEREOSCOPIC WIND MAP
ENLARGED SECTION OF THE STEREOSCOPIC WIND MAP
Large weather maps, drawn with colored chalk on a ground-glass base, may be seen at certain produceexchanges and railway stations, on the “boardwalk” at Atlantic City, and in the Capitol at Washington. Motion-picture weather maps, made from series of maps showing conditions at successive intervals of time, have been prepared experimentally in this country and abroad.
The reports used in the construction of weather maps are telegraphed from the stations in cipher, in order to save expense. In Europe groups of figures are used for this purpose, but the United States Weather Bureau makes use of a word code, which offers the advantage over a figure code that, as a rule, mistakes in the telegrams can easily be detected by anybody familiar with the code. The American weather code is something of a literary curiosity. In each of the many thousand words it contains there are certain significant letters, and these must fall in certain sequences in order to convey the information required. The English language has been ransacked—and somewhat stretched—to secure the necessary words. Observers consult the code book in enciphering their reports, but translating is easily done without the book by those who have mastered the relatively simple principles on which the code is constructed.
SIMPLIFIED WEATHER MAP FOR JAN. 25, 1905, 8 A. M., EASTERN STANDARD TIME
SIMPLIFIED WEATHER MAP FOR JAN. 25, 1905, 8 A. M., EASTERN STANDARD TIME
The language of lines, shadings and symbols used in weather maps can be learned in a few minutes, and it is, as a rule, fully explained on the face of the map. This is true of foreign maps as well as American. A full-fledged weather map is hardly susceptible of reproduction in a book of ordinary dimensions. The simplified map that we show here, taken from a Weather Bureau bulletin, will, however, serve to illustrate some of the features of such publications. The reader should first fix in his mindthe explanations printed at the lower left-hand corner of the map and then study the map in the light of what has been said in Chapter VIII about the circulation and movements of highs and lows. On this map we have an exceptionally well-developed high over the middle of the country and a pronounced low on the Atlantic coast. The former, with clear skies and very cold weather, constitutes a cold wave. The latter is attended by a widespread snow storm and, as may be inferred from the crowded isobars, by stormy winds.
Now bear in mind the fact that charts identical with this one, except that they contained much more detailed information, were issued in all the more important cities and towns of the United States on the morning of January 25, 1905, about a couple hours after the taking of the morning observations, at 8 a. m., Eastern time. The same morning, weather forecasts, cold-wave warnings and storm warnings, deduced from this map, were issued to some hundreds of thousands of addresses by telegraph, telephone, mail, and messenger. The map itself conveys information comparable in interest to the news of public events published on the first page of the newspapers the same day. The forecasts and especially the warnings are, in such a case, worth millions of dollars to the people of the United States. The following account of the cold wave appears in the Annual Report of the Chief of the Weather Bureau for 1905:
“A severe cold wave appeared over the Dakotas, Minnesota, Nebraska, and Iowa on January 24, 1905, and on the 25th covered the central and upper Mississippi valleys and extended over the northern portions of the east Gulf States, the line of zerotemperature reaching into northern Tennessee. On the 26th the cold wave covered Florida, and temperatures below freezing were reported as far south as Tampa and Jupiter. At the latter place, the minimum temperature, 24 degrees, equaled the lowest ever recorded since the establishment of the Weather Bureau station at that point. Considerable damage was done to orange trees where groves could not be fired or protected. Ample warnings had been given of the expected low temperatures.”
The subject of making forecasts from a weather map is one concerning which some big books have been written, and it cannot be dealt with very satisfactorily in the brief space at our disposal. There are two cardinal rules—viz., (1) the weather has a characteristic distribution in relation to the distribution of barometric pressure, and (2) pressure systems, with their attendant winds and weather, move, in a general way, from west to east—but these rules require various qualifications and are subject to various exceptions. Thus highs and lows generally take rather circuitous routes in getting, eventually, to the eastward, and sometimes they break up or fade out. The high shown on the annexed map actually moved much more south than east during the following twenty-four hours, while the low moved up the coast; i. e., more north than east. These were, however, the movements expected by the experienced forecaster.
Well-developed highs are nearly always regions of clear weather and, in winter, of cold weather. Lows are attended by clouds and precipitation; rising temperature usually precedes them and falling temperature follows them. The professional forecaster recognizes several types of pressure distributionother than ordinary highs and lows, and they, also, have their characteristic winds and weather. The seven typical forms of isobars, as classified many years ago by R. Abercromby, are: Cyclone; anticyclone; secondary; V-shaped depression, or trough; wedge of high pressure; col, or saddle, between two anticyclones; and straight isobars. These may be combined in a variety of ways on the weather map. The forecaster learns to classify these combinations consciously or subconsciously, and grows familiar with their habits and mannerisms. Forecasters spend a good deal of time in studying the files of weather maps for past years; but the results of such studies are not easy to reduce to definite statements. Scientific forecasting is, in its present stage, almost wholly empirical. The dependence of weather changes upon the phenomena of atmospheric circulation is generally easy to make out, but the vagaries of winds and pressure are still in the main mysterious; notwithstanding such interesting developments as (1) the much-discussed rules of M. Gabriel Guilbert for predicting the movements of barometric depressions from abnormalities in the force and direction of the winds; (2) the systematic charting of “isallobars,” or lines of equal pressure change, associated especially with the name of Dr. Nils Ekholm; and finally (3) the hypothesis of a sharp line of demarcation between masses of equatorial and polar air along the so-called “polar front,” forming the basis of a system of forecasting that originated at the Geophysical Institute of Bergen, Norway, and has had a marked influence upon the methods of forecasters in other parts of the world.
As to the practical results of this empirical art, one point of the utmost importance is commonlyoverlooked by the public when it complains about the mistakes of the forecaster. He is required to make forecasts of weather day after day, regardless of the kind of map that is laid before him. Sometimes the map is so featureless (or, as the forecasters say, “flat”) that there is little in it on which to build a forecast. At other times there is an abundance of features, but they are in process of rapid and disconcerting change. In either case the ordinary day-to-day weather forecast is likely to go astray. The brighter side of this picture is that the atmospheric phenomena that count heavily in terms of dollars and imperiled human lives are not found on “flat” maps, and, when they appear on the map, generally behave in a simple, straightforward way. In other words, such events as great storms and cold waves are far easier to forecast than everyday weather, and it is the successful prediction of these events that furnishes the principalraison d’êtreof an expensive telegraphic forecasting service.
Since weather predictions serve a variety of purposes, many different kinds of forecasts and warnings have been developed by meteorological services. In this country there are, first of all, district forecasts and local forecasts; the former, covering whole States and groups of States, being issued at a few main forecasting centers, while the latter, applying to a single town and its vicinity, are issued at a large number of the ordinary Weather Bureau stations. There is a long list of forecasts and warnings intended for special classes of the community; indeed the specialization of forecasts is carried so far that an individual citizen or a single business firm can generally obtain, by asking for it, a forecast of any specified predictable feature of the weather for aparticular place. The established types of special prediction issued regularly, or when conditions warrant, include wind and weather forecasts and storm warnings for mariners; shippers’ forecasts, relating to temperatures injurious to perishable goods; aviation forecasts; “fire-weather” warnings, issued when the weather is conducive to fires in the western forests; avalanche warnings; and several different kinds of advices for the benefit of agriculture and horticulture. The United States Weather Bureau, although it is not the only branch of the Government that carries on work in hydrology, is the one charged with the duty of issuing river-stage predictions and flood warnings. An elaborate organization is maintained for this purpose, and the results are extremely successful.
The period of time covered by an official weather forecast is generally from one to two days. In this country the morning forecast is ordinarily for 36 hours from 8 a. m., and the evening forecast for 48 hours from 8 p. m., but occasionally the period is extended for an additional day. For some years the Weather Bureau has issued every Saturday a forecast in quite general terms relating to the whole of the following week. These long-range forecasts are made for extensive areas of the country, such as the North and Middle Atlantic States, the Ohio Valley and Tennessee, and the Great Lakes region. “From the weekly forecast,” says an official publication, “a farmer may know whether it is safe to cut his hay at the beginning of the week or whether it would be better to wait till the last of the week; and a produce dealer may know whether it is safe, at a particular time in the early spring, to start a carload of strawberries to a northern market.” TheBritish Meteorological Office follows a more cautious plan. Its regular forecasts are for twenty-four hours, but occasionally, when conditions are fairly settled, announcements are made of what is termed the “further outlook.” The same office sends notices to the agricultural districts when a spell of fine weather, favorable for haying or the like, appears to be on the programme.
There are a few official meteorological establishments that have embarked on much more ambitious undertakings in long-range forecasting. The classic example is furnished by the Indian Meteorological Department, which has issued seasonal forecasts of rainfall ever since 1882. These were originally based upon reports of the snowfall in the Himalaya, abnormalities of which, as noted in the spring, appear to be related to the intensity of the subsequent monsoon rainfall. Eventually the Indian meteorologists began to seek in more remote regions for clues to the character of the Indian seasons, and they believe they have found them; the barometric pressure in South America and at Mauritius, the rainfall at Zanzibar and Seychelles, the Nile flood, and summer rains in Australia all seems to bear some relation to meteorological conditions in India.
The study of world-wide interrelations of weather, although it has not generally, as in the case just mentioned, furnished the basis of official forecasts, has engaged the attention of a great many able meteorologists. We have spoken on another page of the “centers of action” that seem to be such important indexes to changes in the circulation of the atmosphere, with concomitant fluctuations in weather. Telegraphic reports from some of these centers, including the Iceland and Aleutian lows and the Siberianand Azores highs, have helped to guide the Weather Bureau in making its weekly forecasts. Many attempts have been made to predict the weather months in advance from variations in the temperatures of the water in different parts of the ocean or from the distribution of sea ice in high latitudes. Another line of attack upon the problem of long-range forecasting is through observations of solar activities, as indicated by fluctuations in solar radiation, the prevalence of sun spots, etc. Lastly, an immense amount of energy has been expended in efforts to detect definite cycles or periodicities in the weather itself, without regard to their causes. The thirty-five year period of rainfall and temperature variations, announced in 1890 by Prof. E. Brückner, has found a place in all the current textbooks on meteorology, and several other alleged weather periods have been the subject of serious discussion.
From all of which it appears that the professional meteorologist is not at all inclined to discountenance attempts at long-range weather prediction, provided they are made both honestly and intelligently. Unfortunately the vast majority of people who, in all ages, have indulged in this sort of vaticination—and their name is legion—have been either dishonest or ignorant, or both. The world is still well supplied with them, and they are, undeniably, a thorn in the flesh of the scientific forecaster, who sometimes sees his predictions confounded with theirs by the public, and who commonly incurs the charge of jealousy and narrow-mindedness because he declines to acknowledge brotherhood with the cranks and impostors who hang about the outskirts of his profession.
Quack weather predictions are nearly always made for long periods in advance, and their popularity depends upon the fact that they give the public something—however fallacious it may be—that science does not attempt to give. The making of such predictions appears to be a particularly easy way of acquiring both fame and fortune. In this country there has hardly ever been a time when some exponent of this industry did not enjoy a nation-wide reputation. It is a satisfaction to record, however, that foreign countries produce the same sort of celebrities. Dr. Gustav Hellmann, writing in Germany, has recently published an extremely interesting account of the famous “weather prophets” of the 19th and 20th centuries. Their geographical distribution is given as follows: Belgium, 2; Germany, 36; England, 25; France, 14; Italy, 2; Austria-Hungary, 8; Russia, 1; Sweden, 1; Switzerland, 5; Spain, 2; North America, 9. The list for the United States is, to be sure, conspicuously incomplete, but we need not grieve over the fact that the fame of the American prophets omitted from the list has not spread to the Old World.
The almanac is, as it has always been, the chief stronghold of long-range weather predicting. Nobody knows to what extent the almanac prognostications are taken seriously by the public, or are meant to be by the publishers. It is to be feared that the percentage of the population that “swears by them” is not inconsiderable. Almanac publishers would undoubtedly perform a public service, and perhaps save themselves some pangs of conscience, if they would append to their weather predictions the statement that, like the portrait of the gentleman who displays his anatomy to the signs of the zodiac at thefront of the book, they are published merely for the sake of keeping up an old custom, and if they would conclude every almanac with the following candid avowal, which we find in Gabriel Frende’s “Almanack and Prognostication” for 1589: