1942: Meteorology

Researches in meteorology have been intensified as a phase of the war effort. However, new findings have not been generally released for publication and probably will not be until the war's end. Never in the history of man has a knowledge of aero-dynamics been of such critical value as today and never has there been greater assurance that research in this field will continue to have support. Commercial aviators will need the assistance of meteorologists after this war is ended quite as much as military aviators use it now.

Meteorological Literature.

The growth of interest in meteorology was evidenced in 1942 not alone by the publication of numerous short papers, but by a stream of books, some of them especially prepared for pilots. A few of their titles are significant: Basic Weather For Pilot Trainees, issued by the War Department; Meteorology and Air Navigation, written by an instructor in Civilian Pilot Training; Weather Guide For Air Pilots, Navigation and Meteorology and Oceanography for Meteorologists. Other books of a more general nature are: Weather and the Ocean of Air, Astronomy, Maps and Weather, and Elementary Meteorology. In addition, several other books treating this rapidly advancing field were on press as the year closed.

A comparison of the contents of these books and those of as recently as ten years ago is impressive for the number of new concepts revealed and the expansion of vocabulary. Probably no field has advanced so rapidly in modern times as has that of meteorology with respect both to theory and application. The use of high-level air data is striking. Those for 5,000 feet, 10,000 feet and even higher levels are now of as great significance as those at sea-level. Only some 25 to 30 years ago, a few lone meteorologists toyed with scant data from such levels and advanced notions that they could be invaluable adjuncts to forecasting, but gained little hearing. And such ideas as air-mass analysis, the wave theory of cyclones and isentropic analysis were yet to reach full bloom for usable purposes.

Tropical Meteorology.

What effect the war will have had upon research in tropical meteorology must remain unknown until the last shot is fired. With the intense U-boat campaign waged by the Axis powers against United Nations shipping in Caribbean and associated waters, not only observations must have been curtailed but their relay by radio to shore stations must have been restricted, particularly during the first eight months of 1942. One reliable report indicated the exceptional and fortunate circumstance that there had been no hurricanes off the southeast coast of the United States between January and the late summer of 1942. On the other hand it is conceivable that new methods of forecasting hurricanes and other phenomena may have been worked out or important new contributions made. What the Japanese meteorologists and those of the United Nations have learned in the tropical areas of the Far East must also remain unknown to the world until after the war is ended. Undoubtedly aviators made significant observations in great detail over many islands which heretofore have been classified as regions to be studied in the indefinite future.

Cloud Study.

Increased attention has been paid by many individuals to cloud studies since they have been deprived of the usual standard Weather Bureau reports as bases for forecasts. Likewise professional meteorologists have shown increased interest in clouds. They teach aviators to recognize cloud types and their structures in relation to the kind of weather which may be expected. Thus forecasting based upon cloud types will have been advanced in consequence of the war.

Research.

Research in the five university meteorological institutes went on apace and the training of men in and for the military services likewise. A special committee consisting of one representative from each of these institutions was organized to advise in the training program for meteorologists for the war services. In addition, the teaching of meteorology was greatly expanded in many other universities and colleges.

Studies in micro-meteorology have proceeded in various regions, some under the direct supervision of the national government and others with the latter's partial assistance. These investigations it is expected will add much in the course of time to our knowledge of the local behavior of the air in relation to passing cyclones and anti-cyclones and may shed light too upon the occurrence of certain types of plant life in places where seemingly they should not grow.

Mention of the opening of the military road 'Alcan' between the United States and Alaska in a review of meteorological progress may seem out of place. However, it is noted here, because this road will make regions heretofore remote, readily accessible and undoubtedly will lead to the establishment of observation posts that will contribute much new data of value to our understanding of the movement and perhaps origin too, of cyclonic storms. Additional light may be shed upon those storms which popularly but probably erroneously, had been thought for years to develop in the Medicine Hat region.

The Laboratory of Tree-Ring Research of the University of Arizona, released new data on the subject of variations in precipitation over long periods of time, upwards of centuries. Such meteorological data, depending upon their reliability as indices, may be helpful in the interpretation of climatic changes. These studies are sometimes referred to as dendrochronologic. This type of investigation, first stimulated by Dr. A. E. Douglass of the Carnegie Institution several decades ago has long since attracted world-wide attention.

1941: Meteorology

The military situation continued to be a stimulus to research in Meteorology. Greater emphasis was placed upon applied meteorology than upon theoretical owing to immediate Army and Navy requirements. Many meteorologists devote all of their time to research in behalf of defense. Some of the findings are temporarily retained as military secrets and hence may not be revealed until the end of the war.

Research.

Expansion of departments and institutes of Meteorology has gone on apace. As an illustration of the vigor of this activity, may be cited the Institute of Meteorology at the University of Chicago which opened in the middle of 1940 with fifteen students taking advanced training and concluding its first year with some sixty-five or more men in regular attendance. The researches of this institute have been extended to include the measurement and recording of cosmic ray intensities. A hydrodynamic laboratory has been planned and special studies of the circulation of the atmosphere with reference to improvements in long-range forecasting were brought under way.

Researches in the field of micro-meteorology have continued. These involve detailed observations made at stations spaced a few miles apart or lesser distances thus affording enough data when plotted to reveal the internal dynamics of air masses as they move across the earth's surface. These studies are contributing to a better knowledge of the behavior of atmospheric moisture and the allied problems of evaporation, floods and run-off.

Lightning Discharges.

New light has been shed upon the phenomenon of lightning discharges or 'strokes.' The Westinghouse laboratories became interested in determining 'safe places' for man during thunderstorms. Among their experiments was one involving the discharge of a bolt of artificial lightning with a strength of 3,000,000 volts against the steel top of an automobile. A driver was seated at the wheel and felt no effects. The current was discharged to the earth through a tire and left only a small burn on the metal top of the car at the point of contact. This experiment confirmed the well known fact that a metal cage serves as an electrical screen. Nevertheless, the results of applying a charge as great as that of natural lightning to a metal enclosure gave satisfaction to the observers. These same laboratories pursuing the study further, concluded that the out-of-doors is the most dangerous location for the human during a thunderstorm. Most deaths from lightning stroke occur in rural regions and on level open areas.

Ocean Currents.

At the Scripps Institution of Oceanography, La Jolla, Calif., investigations of the relation between ocean currents and weather continued to show progress. While for many years meteorologists have been familiar with the heating and cooling effects of ocean waters upon air masses, specific effects are now being determined. For example, certain currents radiate their heat irregularly instead of in a constant flow. The Kuroshio gives off large amounts of heat as it flows southward in the eastern Pacific. This uneven distribution of heat, combined with the effects of evaporation from the sea surface has its repercussions in the building up of low pressure areas over the ocean in winter. This pressure reaction in turn affects conditions over considerable areas of both the ocean and adjacent continents. Some apparent climatic changes, probably only cyclical, have been noted in the Galapagos Islands and along the dry west coast of South America, due to a shift in the Humboldt current. The temperature has risen and rainfall has increased.

Importance of Weather Forecasts during Wartime.

In 1939 the British attempted to prevent Germany from securing weather data from points in northern North America or over the northern part of the North Atlantic Ocean. The purpose was to handicap Germany in such military activities on the continent or the ocean as might be planned in relation to the weather. A question was raised as to the probable consequences of this effort. The answer seems to have been given late in 1941 by a U.S. Navy report, which related the capture of a German crew with equipment for making weather observations and for sending radio messages, while attempting to establish itself upon the east coast of Greenland. Since a forecast of the weather over the eastern Atlantic and western Europe depends largely upon the availability of data from places westward, that is, since northwestern European weather is the consequence of the westward drift of cyclones and anticyclones, absence of data from the North American region greatly handicaps European forecasters. In this somewhat negative manner, we have added convincing evidence that the assumptions just made, assumptions which have been held for many years, still hold true.

Tropical Meteorology.

The establishment of United States naval bases in the Caribbean has aroused new interest in tropical meteorology. These studies focus largely upon the origin, development, and movement of air masses in the tropics. An understanding of the great Azores permanent high pressure is especially pertinent in relation to the eastward movement of cyclones, particularly of hurricane proportions. The play of 'cold' and 'warm' fronts as affected by local atmospheric conditions and in turn their influence upon the local atmosphere are other phases of the complexities of tropical climates, particularly in the Caribbean area.

U. S. Weather Bureau.

The year 1941 marked the fiftieth anniversary of the U.S. Weather Bureau's civilian status. In 1891 it was transferred from the U.S. Army Signal Corps, where it has been since 1870, to the jurisdiction of the United States Department of Agriculture. In 1940 it was shifted to the Department of Commerce. During this half century, the Bureau expanded enormously. Originally there were less than 100 observing stations. Today there are 800 stations. In addition to forecasting the weather from day to day, many special services have been added, such as Flood, Hurricane and Special Frost forecasts. The Storm Warning Service has been greatly augmented. Some 50 radiosonde stations have been established where observations are made twice daily. Forecasts have been notably improved, thanks to a change from more or less empirical methods to more exact bases involving the now well known air-mass analysis.

Coincident with the completion of these years of service the Weather Bureau has changed the character of its daily map. Instead of drawing the map based on observations made at 7:30 A.M. it is prepared from data taken at 1:30 A.M. Only two isotherms, freezing and zero, are shown in place of isotherms for every ten degrees which appeared on older maps. More actual data are placed on the face of the map next to the station than have heretofore been recorded. Also cold and warm fronts are indicated. All of these improvements are in line with, and are the outgrowth of, general meteorological progress which the Weather Bureau has made especially during the past ten years. The map issued at headquarters in Washington will as heretofore show more detail than maps published at outlying stations.

1940: Meteorology

The year 1940 witnessed continued rapid advances in the field of meteorology, stimulated as in other recent years by the progress of aviation, particularly commercial, and by the general urge for improved long range weather forecasts. While no radical departures have been recorded, refinements of theories and of instruments for observations have been made.

For the first time since the adoption of the millibar as a unit of measurement of air pressure, this unit made its appearance upon daily weather maps other than the series issued from the Washington office. Isobars are labeled in both millibars and inches, the latter eventually to be entirely discarded. The millibar is a very small unit but much more accurate than the inch and is defined as a pressure of 1,000 dynes per square centimeter. (A dyne is approximately equivalent to the weight of one milligram.) In fact, whereas the inch is an index of length, the millibar is a unit of pressure which is actually what is measured. A comparative scale on the weather map enables persons unacquainted with the millibar to interpret it in terms of the inch. Thus the former standard air pressure of 30 inches, long adopted as the dividing line between high and low pressures, is equivalent to 1,016 millibars. Isobars are drawn at intervals of 3 millibars.

Five-Day Forecasts.

With the cooperation of the Massachusetts Institute of Technology, the United States Weather Bureau began the issuance of five-day forecasts in place of its former weekly predictions. The forecast is still somewhat experimental but sufficiently dependable to warrant publication for use. It is based upon recent accumulated knowledge with respect to air flow and particularly upon the relationship between upper air behavior and that at surface levels.

This forecast differs from the seven-day predictions in that departures from the normal are emphasized rather than absolute conditions. Thus instead of stating what the specific temperature or amount of precipitation will be, the probable deviation from the normal for the region is described. For example, temperatures will be 'normal,' 'above normal,' or 'below normal'; rainfall will be 'light,' none at all, 'heavy,' or 'moderate.' Trends and other general characteristics of the weather to be expected are included, all based upon averages over a period of years, combined with current data and present knowledge of atmospherics. Studies of averages of both surface and upper air data are especially important as bases for these forecasts.

At present, the forecasts are released to the District Forecasters of the Weather Bureau, who in turn have the privilege of making them more specific for their respective districts and localities. They may even deviate from them if their knowledge of the local region warrants so doing. The men issuing the five-day forecast recognize their own limitations, with respect to predictions for certain types of regions such as the western mountain areas, and therefore are willing to allow some discretion to the District Forecaster. Likewise since no attempt is made to predict for minor daily variations, nor are refinements introduced for small areas, the District Forecaster is permitted to introduce modifications based upon his own experience in the region.

As a further aid to forecasting, not only for land areas but for the sea as well, the United States Coast Guard, in cooperation with the Weather Bureau, stationed two ships one-third and two-thirds of the distance between the Bermuda Islands and the Azores. These ships transmit regularly 6-hourly surface observations, two daily pilot balloon observations and one radiosonde report daily. Special observations are made at other times upon call from other ships or from aircraft. The surface report includes: wind direction and velocity, state of the weather, barometric pressure, visibility, temperature, clouds and height of ceiling. The pilot balloon reports consist of data on wind direction and velocity at different levels, while the radiosonde report involves pressures, temperatures and humidity of the upper air. While the stationing of these ships is due immediately to the reduction in number of ships at sea owing to the war, this service might be profitably continued after the war has terminated.

Automatic Weather Stations.

Additional observations over the earth's surface made at isolated points have long been a need, but to station observers in such centers has never been practicable. Upon the request of the Navy the U. S. Bureau of Standards has succeeded in designing an 'Automatic Weather Station' to be placed at these isolated spots, particularly islands, where they will need servicing not oftener than once in two or three months. (Such stations can, of course, be set up in other remote localities such as on mountain heights.) Using the radiosonde principle, the instrument will send out at six-hour intervals, observations on the force and direction of the wind, air temperature, atmospheric pressure, relative humidity and amount of rainfall. The signals sent out by this instrument can be received with reliability at distances upwards of 200 miles. Power is supplied by special storage batteries, in some cases charged by wind-driven generators.

The Mechanical Voice.

The year 1940 seems to have been especially marked by improvements in facilities for making observations and disseminating data and forecasts. So it is worthwhile to note the experience derived from the 'mechanical voice' first tried out in 1939. This voice answers telephone requests for the immediate weather forecast. The inquirer telephones a given number, and when connected, at once hears the forecast from a special type of recording. The forecast is issued regularly four times daily and occasionally a special forecast is introduced if a critical change seems imminent.

In the first experimental trials in New York City, over 4,000 inquiries were made in a single hour. Upwards of 80,000 calls have been recorded in a single day. These numbers stand out in contrast with slightly more than 500 calls in a day as the maximum which could be handled direct by the local Weather Bureau office. As this new service, now also available in Chicago, and Newark, New Jersey, is extended to other cities and many more thousands of persons are accommodated, the public no doubt will become increasingly willing to support appropriations for further meteorological research.

Research.

Still another contribution to the advancement of meteorology was marked by increased opportunities for research in two outstanding universities. One announced a new department and the other a new Institute of Meteorology. Both have sufficient finances to enable them to provide adequate equipment for advanced studies. Without doubt the United States now stands first among the nations in the number of institutions of various types which have both men and materials of the highest order available to assure progress in the field of meteorology. Inclusive of stations associated with these institutions, there are now some 34 regular aerological stations in this country — a world record. Note should also be made of the continued revolution in Weather Bureau practice. The shift is from the earlier more or less empirical and somewhat 'instinctive' bases for forecasting to a practice based upon the most advanced scientific procedures.

In a war-torn world one might assume that the warring nations would have little time to press the academic aspects of atmospherics. A particularly noteworthy exception is the U.S.S.R. Observations along its Arctic coast have been continued in the vigorous pursuit to establish safe sea routes. These observations include undersea, surface, and upper air data. Owing to the high latitudinal location of the observing posts, these data should lead in an important way to the uncovering of further information relative to the general circulation of the atmosphere and perhaps to more dependable weather forecasts.

1939: Meteorology

While progress in the field of meteorology during 1939 was not spectacular, neither did it lag. Research went forward to develop greater accuracy in both short range and long range forecasting. The use of that marvel of atmospheric recording devices, the radiosonde, was extended and the instrument itself improved.

The U. S. Weather Bureau continues to advance its hurricane forecast efficiency in the low latitude Atlantic Ocean region. A greater number of upper air observations than ever before is now available and a higher frequency of observations, both at sea level and in the upper air has been established. Some eighty stations in the West Indies and the Caribbean supply data twice each day and steamships plying southern waters report several times daily during an impending or suspected hurricane in accordance with Weather Bureau requests. Besides, additional radiosonde stations have been opened at strategic points and more are planned.

It has long been the belief of some of those associated with weather forecasting that an accurate knowledge of the behavior of the atmosphere over the oceans is of greater importance for accurate daily predictions than those over the land for which predictions are made. If this philosophy be true, then a large number of daily observations widely scattered over the oceans is vital.

The coordination of pressure variations in the Iceland and Aleutian Lows may eventually be definitely related to the movement of centers of action across North America and in consequence the accurate prediction of such movements may be realized. In this connection should be noted the continuation of the program of experimental five-day weather forecasting by the Massachusetts Institute of Technology based in large part upon atmospheric pressure readings over the ocean. Thus far the institute has corroborated the theory of meteorologists of some thirty years ago with reference to the apparent correlation in behavior of the great permanent pressure areas over the Atlantic and Pacific Oceans.

Publication of Abstracts.

The announcement of a section in the publication Biological Abstracts to be known as Bioclimatology-Biometeorology is of considerable importance. It will be devoted to abstracts of papers in the fields of biology, medicine and agriculture which reveal the close associations of climatological or meteorological phenomena with these sciences. The ecological relations of such elements as temperature, moisture and winds to the distribution of plants and the lower animals have been long recognized. Similarly, although less convincingly, correlations have been attempted between atmospheric conditions and man's physiological behavior. Then too, crops and weather have had their share of attention. In all these fields there has been an intensification of activity reflecting a rapidly growing interest. The literature is scattered. Hence, the abstracting of these papers in a single periodical should be advantageous to those interested not only in keeping themselves conveniently abreast of the activities of others, but perhaps also in the establishment of common research techniques and the reciprocal utilization by many of the research workers, of the results of each others' endeavors.

Micro-meteorology.

Studies in micro-meteorology continued in the Muskingum Valley of Ohio as a part of the national government's conservation program. This work which involves the collection of data from hundreds of observation posts within a relatively small area, points toward a better understanding of the dynamics of cyclones and anti-cyclones and the effects of precipitation upon soil erosion and river floods. Among some of the important data derived from this research are those bearing upon great variations in intensity and rates of rainfall within single rain storms and the relations of these elements in the presence of different types of vegetation to rates of erosion and run-off.

Antarctic Expedition.

Another Antarctic expedition under Admiral Byrd sponsored by the U. S. Government got under way. While this expedition was organized primarily to validate a claim to be made by the government to lands which Admiral Byrd has already explored, it has for its object as well, the gathering of more meteorological data as a basis for studies of possible relationships between Antarctic atmospheric behavior and weather changes over other parts of the earth. A large volume containing data collected during his last two expeditions was published late in the year by the U. S. Weather Bureau under the title: Meteorological Results of the Byrd Antarctic Expeditions; 1928-30, 1933-1935, Supplement No. 41.

War Censorship.

An account of the status of meteorology during 1939 could not be satisfactory without reference to the censorship of weather news and the dissemination of data by the warring powers. Not only was reference by radio commentators to the state of the atmosphere prohibited but the hand of the censor reached the North American continent by way of preventing the printing of Canadian weather observations on the daily maps issued by the U. S. Weather Bureau. Publication of such records a week or ten days after they were made was permissible. Thus the daily weather map beginning in early September took on a more or less 'decapitated' appearance since the absence of readings for Canadian stations necessitated the termination of isotherms and isobars at our northern border. It will be a matter of great interest after the peace is declared to learn to what extent, if at all, these checks against weather data falling into the hands of Germany handicapped their forecasts and therefore, military maneuvers. Advance in the technique of forecasting facilitated by air-mass analysis may have greatly reduced the effectiveness of this censorship.

1938: Meteorology

Advances in the science of meteorology continued during 1938 at an accelerated rate, owing not only to increased public interest but to the growth in popularity of aviation and the consequent demand for greater safety in flying. In spite of important improvements in the construction of airplanes and their reduced sensitivity to atmospheric conditions, an accurate knowledge of the behavior of the atmosphere still remains an essential to the success of the aviation industry. As always, the primary objective in advancing the field of meteorology is increased accuracy in weather forecasting.

The United States Weather Bureau has joined with the Massachusetts Institute of Technology to experiment in long-range forecasting. It is their hope to be able to predict the weather for periods of weeks and perhaps even seasons ahead, with relative accuracy. The results of these experiments naturally will not be available to the public for several years. Blue Hill Observatory, Milton, Massachusetts, is closely associated with this program.

Direct Observations.

Both short-range and long-range forecasts depend upon an understanding of the behavior of the upper air as well as that at surface levels. To this end, frequent observations of temperatures, barometric pressure, and humidity over wide areas in the upper levels are essential. The problem of obtaining such data at low cost has approached nearer solution during the past year, as improvements have been made in that remarkable instrument known as the radio-meteorograph. (This term will probably remain in use for a time, although the United States Weather Bureau has adopted the word 'radiosonde' in conformity with French and German usage.) One of the most recent refinements in the instrument has consisted in the replacement of the hair hygrometer by an electrical hygrometer especially adapted for a quick recording of the humidity when the balloon carrying the radio-meteorograph is in very rapid ascent.

The radio-meteorograph is steadily replacing the airplane for use in making upper-air soundings. This instrument sent aloft attached to a small free air balloon may reach heights ordinarily of well over ten miles, sending back the desired data at frequent intervals during its ascent. (In 1938 a record height of 95,000 feet was reached.) Not only are the hazards of airplane ascents avoided, but the cost of obtaining observations in this manner is lowered. The major objection involves the likely loss of the radio-meteorograph itself. This will be less serious as the cost of the instrument is reduced to negligible proportions.

Theoretical Considerations.

Besides advances in methods of making direct observations of the state of the atmosphere, there has been not a little progress in theoretical considerations. The number of men, particularly younger men, devoting attention to the purely mathematical aspects of meteorology continues to grow. Their investigations involve interpretations of the general planetary circulation of air, vertical cross-sections of air masses, and the behavior of the air in cyclones and anti-cyclones which are revealed by the daily weather map. This work includes synoptic analyses with special reference to rain-storms, snowfall, thunderstorms, flooding, and violent tropical cyclones. Supporting studies in micro-meteorology have been continued. Among these is the collection of data in the Muskingum Conservancy district of Ohio as a part of 'Studies in Climatic Factors of Soil Erosion.' These data present a highly detailed series of observations of the rate of horizontal translation of atmospheric conditions at the earth's surface and may constitute the basis for interpreting mathematically or otherwise the behavior of the circulation of the air within cyclones (lows) and anti-cyclones (highs) under specific circumstances.

Climatic Variations.

Investigations are also going forward in the field of climatic variations. Just as the 'man-on-the-street' has observed what to him seem to be changes in climate 'since he was a boy,' so the meteorologist has noted changes in intensity of the seasons, which he seeks to interpret not as true climatic change but as possible cyclical variations. Correlations with sun spots and other manifestations of solar activity are still in progress. Data are being collected relative to the shifting of ocean currents, identification of the phenomenon occurring through the automatic recording of temperatures of sea-water by ships which regularly cross the major currents.

At the International Geographical Congress held in Amsterdam, July 1938, a special report was presented by the Commission of Climatic Variations of the International Geographical Union. The papers prepared for this report fall in such categories as 'Pre-Pleistocene Changes of Climate,' 'Climates of the Recent Prehistoric,' 'Present-Day Variations,' and others. Interesting progress has been made in observing the relation between climate and tree growth. Students of this subject, having already satisfied themselves that three rings serve as indices to climatic variations of the past, are now attempting to derive a formula from these correlations which will enable them to predict probable cyclical changes of the immediate future.

Marine Meteorology.

The field of marine meteorology is being forwarded through the steady increase in observations by ships on the high seas, by various exploratory parties, and by workers in scientific laboratories along the coasts who are interested in the life of the sea or in the behavior of the ocean itself.

Medical Meteorology.

Another division of meteorology which has been advancing slowly might be termed medical meteorology. Only a few persons have turned their attention to this subject. One of the outstanding students of this subject in the United States concludes that two phases of weather are paramount in their effect upon man. One is the mean temperature level in relation to the rate of heat loss from the body, and the other is the effect of atmospheric instability upon physiological adjustments. This vast field is yet to be fully explored.

Other Fields.

Other fields in which the science of meteorology is finding direct application are radio, agriculture, hydrology, and general business. Techniques in forest-fire weather forecasts have improved, also methods for predicting the formation and dissipation of fog and clouds over coastal waters.

Notable Phenomena.

Perhaps two of the most notable meteorological phenomena of the year were the 5-day rainfall in Southern California, February 27 to March 4, and the New England hurricane of September 21. The rainfall in California was the heaviest recorded for such a period since accurate records have been kept. The hurricane is reported to have been the worst in the history of New England, although claims for severity have been challenged by some persons. Even though the damage from both storms mounted high, the resultant losses may not have been in vain; for they have helped to emphasize the desirability of more observation stations and of increased public financial support for the advance of the science of meteorology.