February 2008

Fifty years ago

WMO Bulletin Vol. VII, No. 1
January 1958

  cover

The picture on the cover

“Any meteorologist who has attempted to put together information for the whole globe will realize that the differences of practice of the various Governments … place such an enterprise outside the limits of possibility for any but a few individuals, who must have at their disposal the facilities of such a library as that of the Meteorological Office … The alternative that the few workers who deal with the meteorology of the globe should each one of them separately and severally have to go through an identical process of laborious compilation, reduction and tabulation in order to obtain a result which is of itself an indispensable stepping-stone to a comprehension of the meteorology of the globe, is sufficient to justify any establishment in making public a compilation for the benefit of the world at large.”

The above words, written by Sir Napier Shaw in his preface to the 1914 issue of Réseau mondial, might well have been written nearly 40 years later as an argument in favour of creating the IGY Meteorological Data Centre, the work of which is described in this issue of the Bulletin. The picture on the cover shows two members of the staff of the Centre in the process of checking and registering some of the IGY forms which are now arriving at the Centre at the rate of several hundreds per day.

 

Contents

The contents of the January 1958 Bulletin covered, as well as the IGY Meteorological Data Centre at work, meteorology and crop protection, and the presidential address at the second session of the Commission for Aerology entitled “The conquest of the third dimension”. The ninth session of the Executive Committee, the second session of the Commission for Bibliography and Publications and a seminar on hydrological forecasting and the water balance were also reported on.

 

The IGY Meteorological Data Centre at work

Now that the International Geophysical Year has run a third of its course, research workers are no doubt looking forward to the day when the observational data they require will be in their hands. The collection and distribution of these data are in fact two absolutely vital aspects of the IGY programme, for there would be little point in organizing such a vast project without making adequate arrangements.

… the IGY Meteorological Data Centre (MDC) … was set up in the Secretariat of WMO in Geneva towards the end of 1956. The object of the present article is to describe the work of the MDC, which is in fact unique in the history of meteorology.

Creation of Centre

… The detailed plans for the MDC were worked out by the WMO Secretariat on the basis of proposals made by the WMO Working Group on the IGY, subsequently approved by the Executive Committee.

The MDC came into being in October 1956 with the renting of an apartment at 32 rue de Vermont, Geneva, and the appointment of Dr G. London (formerly the librarian of the Israeli Meteorological Service) as chief. The total staff is now four and one or two additional members will be recruited when required.

Functions of Centre

Prior to the establishment of the MDC, it had been decided that it was essential to have the IGY meteorological data presented in a uniform manner; lack of such uniformity would complicate the task of publishing the data and would make it more difficult for research workers to use the data. Standard forms were therefore devised for the principal meteorological observations and bulk supplies were sent to those meteorological services which did not wish to print them locally. It had also been decided that the main observations would be published on microcards, a careful study of various methods of reproduction having shown that this was the most economical and convenient.

One of the main tasks of the MDC was therefore to develop a system for cataloguing the observations reported on the standard forms as received and to plan their arrangement on microcards. Each microcard, 75 x 125 mm, has space for the photographic reproduction of between 40 and 96 of the original forms in greatly reduced size. The experience gained during the IGY meteorological trial period, which was organized by WMO from 6 to 10 January 1957, proved to be invaluable for future planning. For this 5-day period (pentade), meteorological services entered their observations on standard forms and sent the completed forms to the MDC, where many of them were reproduced on microcards.

The principal meteorological observations of which we have speaking consist of the surface synoptic observations made on land at a selection of about 2000 stations at 0000, 0600, 1200 and 1800 GMT, the corresponding observations made at sea, all the radiosonde and radiowind observations and a selection of the pilot-balloon observations. The MDC has also been made responsible for collecting and publishing the IGY observations of radiation, ozone, atmospheric chemistry and atmospherics.

Principal meteorological observations

First attention is being given to those observations which have to be reproduced on microcards. On receipt, each form is carefully scrutinized and checked to make sure that it has been completed correctly and that all the figures are sufficiently clear for satisfactory photographic reproduction. Wholly unsuitable forms are returned to the originating service for re-copying but if only minor changes are required and the necessary information is available the changes are made in the MD. The forms are then registered in a visible index on special cards, there being a separate card for each type of standard form and for each station. By means of a sliding tab it is possible to see at a glance the dates for which forms have been received from each station. An entry is also made on a microcard register, in which a separate sheet is reserved for each microcard. From this it can be readily seen when all the forms for a given microcard are available.

The forms are then placed in folders and suspended in lateral filing cabinets, here being one folder for each station in the case of Form No. 1 and one folder for each synoptic hour for a group of stations in the case of Forms Nos. 2, 3 and 4. When the complete material for a microcard has been received, the relevant forms are extracted from the folders, arranged according to the planned layout and passed to the Microcard Corporation, which has set up a special photographic unit in Geneva for the IGY.

Details of microcards

One complete set of microcards of IGY meteorological data will consist of four parts which correspond to the four different types of standard forms on which the principal meteorological data are being recorded as follows: Part I will consists of about 2750 microcards containing the synoptic surface observations from land stations (Form No.1). Part 2 of about 4400 microcards containing the synoptic surface observations from sea stations (Forms No. 2 and No. 2(b)), Part 3 of about 6000 microcards containing the radiosonde and rawinsonde observations ((Form No. 3) and Part 4 will consist of about 5000 microcards containing the upper-wind observations (Form No.4).

Allowing a small margin to cover unforeseen additions or changes it has been estimated that the entire volume of the principal meteorological data collected during the 18 months of the International Geophysical Year will be reproduced on 18500

microcards. It will thus be possible to keep the whole collection of about one million original forms reproduced on microcards in 15-16 drawers of any standard-size card catalogue cabinet. The subscription price for a complete set of these microcards is US$ 5990.

The basic principle which was followed in deciding the layout of the microcards was that it must be easy for the user to locate any give observations. In the case of Form No. 1, each standard form contains 20 successive synoptic surface observations made during the course of a pentade. The same layout will be sued for each of the 110pentades of the IGY.

In the case of form No. 2, the forms contain synoptic observations made on board ships at a given synoptic hour on a give day. Each microcard will therefore be limited to observations made at one particular synoptic hour. This also applies to Forms Nos.3 and 4, for which the forms will again be arranged on microcards in accordance with the sequence of WMO station index numbers. As the number of upper-air observations is not the same for every station—some make only one daily, whereas others make up to four daily—there will be four groupings of stations, one for each synoptic hour. These same groupings will be maintained throughout the IGY.

Other observations

Standard forms have also been prepared and issued by WMO for the other types of observations, which are to be collected at the MDC. In all there are two different ozone forms, six radiation forms and four forms for atmospheric chemistry data. A final decision has not yet been taken about the method of publishing these data, as it depends to a large extent of the size of the demand for the publications, which has not yet been determined. They will in any case not be published until after the end of the IGY. In the meantime, the forms are being registered and placed in folders in a manner which will be suitable for whatever form of publication is ultimately selected.

MDC reports

An important function of the MDC, especially during the initial stages of the IGY, is to ensure that all countries are fully informed about the standard forms and other important aspects of the IGY meteorological programme. The main decisions and instructions are contained in the MDC reports, of which 10 have been issued to date in separate English and French versions. [There followed a list of the titles.]

It can therefore be seen that the MDC is a service set up by WMO for the benefit of research workers. Its success depends not only on the readiness of meteorological services to send their data to the Centre—and this is already assured—but also on there being a sufficient demand for the Centre publications. The IGY provides a unique opportunity for meteorological services, universities and research institutes to obtain a truly worldwide set of checked meteorological data in a standard form for a period of 18 months and it must be the hope of all concerned that this opportunity will be widely seized and that these data, which are the result of much painstaking work by observers all over the world, will contribute to solving many of the outstanding problems in meteorology.

 

Meteorology and crop protection

The development of meteorology and of crop protection as organized sciences began at about the same time one hundred years ago. The initial stimulus in the case of meteorology was disasters at sea and the need for a warning service of storms dangerous to shipping. Disaster on land—and in particular the attack of potato blight which led to the Great Famine in Ireland in 1846-47 and the dreadful Phylloxera which ravaged the vineyards of France some 20 years later—played a similar role in giving birth to modern plant protection.

That weather conditions were important in the development of plant diseases and pests was recognized from an early data but this fact had little or no practical application until chemical methods of control had been developed. The earliest of these weapons—the use of Bordeaux mixture against vine mildew—dates back little more than 70 years, lime-sulphur was introduced in 1905 and the bulk of modern chemicals have been developed since 1930.

Experiments soon showed that such matters as the number of necessary applications of chemicals and the proper timing of sprays depended in large measure on weather conditions. Almost all the initial work on this subject was carried out by crop protection specialists because the meteorologists were at that time fully occupied with rapid developments in their own science with the demands of two successive world wars and with the claims made on them by the phenomenal growth of civil aviation. Only in the last few years have the meteorologists at last been able to lift their noses from the aeronautical grindstone and turn some of their attention again to wider horizons. To this new field of agricultural meteorology—or more correctly, to this old field revisited—they bring the progress in knowledge, equipment and organization which resulted from the stimulus of the aviation challenge.

Meanwhile the plant pathologists, entomologists and many other specialists who cooperate in crop protection problems have not been idle. Much new light has been thrown on the life cycle of many plant pathogens and pests and on their reactions to environmental conditions. The organization of plant protection has made enormous strides. The realization that for diseases and noxious insects, just as for the weather, no borders exist and that there is a consequent need for combined international work, spread at first rather more slowly in the case of crop protection than of meteorology but has progressed rapidly in recent years.

This was abundantly clear from the recent IVth International Congress of Plant Protection (Hamburg, 8-15 September 1957). …

The predominating impression that a meteorologist could not help but gain at the congress is the extent to which weather intervenes in virtually every facet of crop protection. Everyone is, of course, familiar with examples of the direct effect of weather on the host plant and on the life-cycles of the pathogens and insect pests. But even when there is not clear-cut environmental influence on the disease itself, meteorological factors may still play a decisive role through their effect on the population level and activity of vector insects. Thus, in England this year, the mild winter and dry spring were most favourable to the aphid which spreads the disease of sugar beet called virus yellows and as a result, the crop suffered the worst outbreak since sugar beet became a principal crop in England.

In control measures against disease or pest, meteorological factors affect each successive stage in turn. The techniques of spray application, especially in the modern forms of mistblowing and aerial spraying, are affected by wind, turbulence and air stability. Phytotoxicity or the injury which the chemical may inflict on the host plant, is often dependent to a greater of lesser degree on weather conditions. If the spray leads to a rise in transpiration rate, crop yields may be materially reduced in a season of low rainfall. The efficiency of the spray and the duration of its effectiveness will be determined in part by whether it is resistant to removal by rain, whether it is reduced by volatilization or sublimation during warm weather in the field, or whether its protective properties are gradually negatived by oxidation or hydrolyzation. Weather conditions before harvest time have corresonding effects on spray residues on marketed crops and must be taken into account in any consideration of toxic hazards to the consumer. Finally the problem of the protection of stored products, whether in clamps, storehouses in the form of packaged goods or in the olds of cargo ships, involves environmental factors.

… Mr F. Schnelle (West Germany) described an instrument for the recording of the duration of leaf wetness, caused either by rainfall or dew, a factor which is of prime importance in the spread of apple scab and of other plant diseases. Mr J.J. Post (Netherlands) spoke on the effect of temperature on the duration of the pupal stage of the codling moth, a pest of the apple crop. His conclusions have practical applications in the timing of control measures against the insect. Other speakers told of the forecasting of potato blight, vine mildew, apple scab, tea blister blight, fruit diseases in general and diseases and pests of the beet crop.

Mr Austin Bourke (Ireland) … gave an introductory talk to this section under the title “Modern meteorology and the epidemiology of plant diseases”. He pointed out that developments in meteorology in the last 40 years had made available tools for the study of environmental influences on plant diseases and pests which are potentially far more powerful than the simple meteorological entities on which much of the pioneer work on disease-weather relationships was based. Examples were given to show how the concepts of air mass analysis, blocking, steering, etc., could be successfully applied to plant disease epidemiology.

… French investigations into the geographical distribution of the physiological races of black rust of wheat had confirmed that certain regions of North Africa, and in particular the Moroccan Atlas mountain area, constitute permanent or semi-permanent breeding grounds from which the spores of the disease are carried by wind to the grain-producing regions of temperate Europe. Observations in south-west England, based on studies of upper-air charts and simultaneous catches of airborne uredospores, gave further evidence that severe attacks of black rust in that area may may be initiated by airborne inocula from southern Europe and North Africa.

To participate as a meteorologist in this well-organized and highly successful congress was at once a stimulus and a challenge. Most of the technical weapons required by the meteorologist to cooperate in plant protection have already been forged for other purposes; and in the few exceptions, e.g. the provision of an adequate network of soil temperature and soil moisture observations, steps to remedy the defect are already being taken. To adapt and apply these weapons usefully to the whole range of crop protection problems in which weather is a vital factor requires a wider interpretation of the role of the agricultural meteorologist in the old-fashioned concept which still tends to persist in some quarters. The challenge to meteorology of modern agriculture can no longer adequately be met by a part-time subsection of climatology but requires the active participation of the synoptician, upper-air analyst, long-term forecaster and research meteorologist. If even a proportion of the meteorological efforts which has so successfully been applied to solving the problems of aviation were now devoted to those of agriculture, which are no less important, the promise of agricultural meteorology could quickly ripen into triumphant achievement.

 

The conquest of the third dimension

Presidential address at the second session of the Commission for Aerology
Paris, June-July 1957

Part I

Present-day science has so thoroughly altered the world, technology has achieved such remarkable advances during these past few years, discoveries have followed on another at such a rapid rate, that it is sometimes wise to step aside from the disorderly road of progress and glance backward in order to measure the distance covered, consider recent developments and put our ideas in order. In this manner, we perceive, among other things, that the fundamental problems that arise are nearly always the same, and that those that we imagined were new are most frequently old problems for which the ever-increasing possibilities of modern technique afford unexpected solutions.

In this era of rockets, teleguided missiles and artificial satellites, it seems to be appropriate … to make a general survey of the development of techniques for exploring the free atmosphere from their commencement, which is closely associated in fact with the beginnings of air navigation (balloon ascents).

Early discoveries ad experiments

In these times, it is difficult for us to imagine the sensation caused in the scientific world by the invention of the barometer during the middle of the 17th century. By his famous experiment in 1643, Torricelli (1608-1647) actually demonstrated that the air possessed weight, whereas up till then it had always been thought that the atmosphere was a medium without substance. When, acting on Pascal’s (1623-1662) advice, Périer climbed the Puy de Dôme to carry out his “great experiment in the balancing of liquids”, in 1648, he was probably making the first measurement of the upper air by man of instruments. It might be thought that the brilliant success of the striking Puy de Dôme experiment would mark the beginning of an era devoted to upper-air measurement; this was not however the case, owing to the insuperable difficulties of mountaineering in those days.

It was not until 1787 that the daring Genevese physicist, de Saussure (1740-1799), succeeded in climbing Mont Blanc. In spite of the serious risks, de Saussure had numerous followers; scientific expeditions were organized in, for example, the Alps, the Andes and the Himalayas, but owing to the difficulties connected with such mountain ascents and their very short duration, the results were somewhat disappointing. The setting up of mountain observatories only began during the middle of the 19th century; we need only mention Puy de Dôme, Mont Ventoux, Pic du Midi, Säntis, Brocken, Sonneblick and Jungfraujoch. Although mountain observatories, in the same way as those on plains, afford the possibility of observing phenomena and recording observational data continuously, they have the disadvantage of supplying upper-air data for a single level only. Moreover, mountain observatories are unevenly distributed over the world’s surface and their data are strongly influenced by topography. Nevertheless, it was by means of mountain observations that in 1876 Hann (1839-1921) discovered the temperature inversion of anticyclones and the subsidence or the air above the inversion.

The first balloon ascents

But let us revert to the 18th century. A new event of paramount importance for the conquest of the third dimension occurred in 1783: the first experiment of the Montgolfier brothers (Jospeh, 1740-1810 and Etienne,1745-1799) at Annonay, followed in Paris, during the same year, by the first aerial voyage between La Muette and Montrouge, by a balloon made of packing canvas lined with paper and inflated with hot air. Physicists immediately realized all the possibilities offered by a lighter-than-air vehicle for exploring the atmosphere. On 1 December 1783, Charles (1746-1822), the inventor of the hydrogen balloon, made an ascent from the Jardin des Tuileries, taking with him a barometer and a mercury thermometer. This first free balloon ascent was the starting point for the scientific exploring of the free atmosphere. The science of aerology was born.

At the end of the 18th century, all the conditions necessary for the development of scientific ballooning were fortunately fulfilled. The requisite measuring instruments, gases lighter than air and impervious envelopes were all available. The barometer had been invented by Torricelli nearly 150 years earlier; Celsius (1670-1756), Fahrenheit (1686-1736) and Réaumur (1683-1757) had invented the thermometer at about the same time, at the beginning of the 18th century; at the close of the century in 1783 de Saussure made the first hair hygrometer. Cavendish (1731-1810) discovered the lightest of the gases, hydrogen 9n 1781, and a little later, in 1784, Van Bochaute discovered the process for making coal gas an the fist balloon inflated with this gas was sent up near Louvain, by Minkelers (17488-1824). The envelopes were made of varnished silk or goldbeater’s skin.

Manned scientific balloon ascents

The era of manned scientific balloon ascents covers the end of the 18th to the first years of the 20th century. In 1784, the year following Charles’s famous ascent, Lavoisier (1743-1794) on behalf of the Académie des Sciences de Paris, drew up a scientific programme of upper-air measurements which caused a lively emulation amongst the aeronauts. Following Charles’s example they all carried at least a barometer and thermometer in the nacelle but most of them were much more attracted by the spectacular and financial aspects of balloon ascents than by their scientific interest. However, there were some praiseworthy exceptions to this general rule. The honour of making the first ascent organized for carrying out a programme of observations with instruments that had been carefully constructed and tested in the laboratory belongs to the Canadian physician, John Jeffries, who had settled in London, and the French aeronaut, Blanchard (1753-1809). They ascended from London on 29 November 1784, and came down at Dartford, 15 km to the ESE of London, after a voyage lasting an hour and a quarter. The following year, they crossed the Pas de Calais and it was during that memorable voyage that angular measurements were first made from the ground which enabled the height of the balloon to be calculated. Among scientific ascents made during the first half of the 19th century, there were the two ascents of Gay-Lussac (1778-1850) and Biot (1774-1862) in 1804, the second reaching an altitude of 7000 (?) metres and that of Barral and Bixio (1808-1865) in 1848, which was carried out in cloud.

As early as 1841, Arago (1786-1853) insisted that during scientific balloon ascents ground observations should be taken at the same time at various points, so that the upper-air measurements could be compared with those made on the ground. He also drew attention to the fictitious nature of many of the results obtained and particularly to the fact that a thermometer attached to the nacelle could not give the true air temperature. On several occasions Arago argued that instruments and methods of observation should be developed which would be capable of providing representative data. Meteorologists have always been faced with the problems of the radiation error which affects upper-air data and of the representativeness of their measurements.

Development of instruments

At about the same time, the British Association for the Advancement of Science devoted its efforts towards the problems of scientific balloon ascents. In 1852, John Welsh, director of Kew Observatory, carried out four carefully prepared ascents. He was the first to employ a thermometer artificially ventilated by hand bellows. The Welsh aspirated psychrometer is the forbear of the Assmann aspirated psychrometer that we are still using today. Unfortunately Welsh’s successors, including the famous Glaisher, did not realize the imperative need to aspirate thermometers if the indicated temperature were to be the true air temperature. This lack of appreciation was fatal to the progress of aerology, and it was only after a lapse of 45 years =, i.e. at the end of the 19th century, that it became possible … to form an accurate idea of the vertical distribution of temperature in the atmosphere.

The 28 ascents carried out by the Englishman, T. Glaisher (1809-1903), from 1862 to 1866, occupy a meritorious place in the history of scientific ballooning. In 1862, accompanied by Coxwell, be beat the height record by reaching a height of 11300 (?) metres, without, however, discovering the stratosphere. He was the first to make use of an aneroid barometer, invented by Vide in 1844, 200 years after Torricelli’s mercury barometer. The use of recording instruments dates from 1881; actually, it was in October of that year that du Havel and Duté-Poitevin carried two barographs in their nacelle – made by the French constructors, Tatin and Richard.

During the scientific ascents made in the 19th century, not only w ere measurements of atmospheric pressure and the temperature and humidity of the air carried out, but also electrical measurements (Gay-Lussac was the first to make use of an electrophore provided with wires of different lengths), magnetic measurements (by means of compasses) and actinometric measurements (by means of black-bulb thermometers) as well as observations of upper-air currents (whose abrupt changes astonished the first aeronauts), of clouds (especially cumulus clouds whose bulges rose more quickly than the balloons) of optical phenomena and of sound propagation Air samples were as taken for ascertaining their chemical composition.

After the doughty deeds of Glaisher and Coxell, holders of the height record, interest in scientific ballooning waned. No outstanding discovery was made which might have revived the enthusiasm of scientific explorers. Furthermore, the limitations of the free manned balloon had become so apparent that scientific ballooning might have completely disappeared before the end of the 19th century had it not been for he setting up of the Deutsche Verein zur Förderung der Luftschiffahrt in Berlin in 1881.

The successes obtained by the balloons used for carrying passengers and letters during the siege of Paris, in 1870-1871, made such an impression on the Germans that, after the war, the German Army formed a balloon regiment equipped with manned and captive balloons. On Angerstein’s initiative, German civil and military aeronauts met and found the Deutsche Verein zur Förderung der Luftschiffahrt for the purpose of promoting aerial navigation. Among the civil aeronauts, the meteorologists R. Assmann (1845-1918), A Berson (1859-1942) and R. Süring (1866-1950) were in the forefront. It is therefore not surprising that the scientific exploration of the free atmosphere was one of the chief concerns of the Deutsche Verein.

Under Assmann’s leadership, German meteorologists carried out an exhaustive study of the scientific equipment used in the French and British ascents and came to the conclusion that further research work was essential for obtaining not only instruments for the laboratory but also instruments adapted to the very peculiar conditions of an ascent, able to respond rapidly to the continual fluctuations of the atmosphere and to record the results of measurements Assmann’s efforts were crowned with successes; in 1891, during an ascent accompanied by Gross, he tried out for the fist time the aspirated psychrometer bearing his name. In 1893, he constructed the ventilated barothermohygrograph, specially designed for hanging from the nacelle of a captive or free manned balloon. Assmann may therefore be considered as the constructor of the first aerological sonde. Improvements to this instrument were subsequently made by Marvin and Bosch.

Although the Deutsche Verein only succeeded by its persevering efforts in postponing the end of scientific ballooning, meteorology is however, indebted to if for the great progress achieved in the field of instrumentation.

Although observations taken from a balloon do not possess some of the disadvantages of those taken on mountains on the other hand they are very expensive and decidedly dangerous. We only need to recall the Zenith disaster in 1875, when Tissandier’s (1843-1899) two companions met their death at about 8800 (?) metres altitude. Not only had it become obvious that at the maximum heights reached one was still a long way from the upper limit of the atmosphere but furthermore that the sporadic nature of the ascents was such as to limit greatly their scientific value.

Stratostat ascents

In spite of the waning of scientific ballooning during the 20th century, the idea of using the free passenger balloon for exploring the terrestrial atmosphere was not entirely abandoned. While the 19th century was notable for scientific ascents in an open nacelle, the 20th century was for closed nacelle ascents, the technique for which was created and developed by A. Piccard. During August 1932, Piccard reached a height of about 17 km. But the Americans Stevens and Anderson improved on this record in November 1935, by going up in their closed stratostat, Explorer II, to a height of 22.5 km. They brought back important results from their expedition, concerning in particular the variation of the chemical composition of the air with altitude, the vertical distribution of the ozone content of the air and the variation of cosmic radiation intensity with altitude, the successive heights reached by Explorer II were ascertained by three different methods: photographs of the terrain, angular measurements made from the ground and by recording the pressure and temperature of the air. It was thus possible to carry out the most compete check of the hydrostatic hypothesis.

Experiments with kites

But we must not anticipate. The shortcomings and disadvantages of free manned balloons compelled meteorologists to look for another method for exploring the free atmosphere. Kites were first of all proposed. These were not an innovation for, as early as 1749, Wilson and Melville had flown kites near Glasgow carrying minimum thermometers and in 1752, Franklin (1706-1790) had noticed at Philadelphia that a kite became electrified under the influence of clouds. These experiments were repeated a great number of times, both in Europe and America.

However, it was not until 1894 that anyone had the idea of suspending a recording apparatus from a kite. It was during August of that year that, at Blue Hill Observatory, Eddy sent up a Richard barothermograph to a height of 436 metres. During the following year, L. Rotch (1861-1912) improved the technique of kite-sounding to such an extent hat in 1897 the Weather Bureau decided to organize a network of 17 sounding stations in the USA. The method is undoubtedly very simple and inexpensive but it can only be put into operation during a fairly high wind and moreover it only enables the lower layers to be explored. It was therefore essential to look for other methods. However it is only fair to state that it was thanks to kites, as well as to captive balloons hat it was possible for the fist time tot form a fairly accurate idea of the wind distribution in the friction layer near the ground. We would also recall that Cleveland Abbe (1838-1916) in the USA, made use of kites for studying sea breezes and that it was by means of kites launched from the deck of the yacht of Price Albert of Monaco that H. Hergesell (1959-1938) was able to make the first observations of trade winds (1904-1906) in the offing of the Canary Islands.

Forerunners of the sounding balloon

The results of the two ascents of Gay-Lussac and Biot caused a considerable stir in the scientific world the 19th century. In 1809, the Royal Society of Copenhagen issued the following questionnaire: What contributions have been made to meteorology up to the present time by balloon ascents? How should experiments be organized by means of smaller unmanned balloons to obtain information inexpensively about atmospheric electricity, the variations with height of the composition of the air (oxygen, nitrogen and carbon dioxide), the direction of air currents, the vertical distribution of temperature and all other quantities? We do not know whether the Royal Society of Copenhagen ever receive any answers in reply to its questions but we do know that 85 years elapsed before a reply was available to the second one, of which the basic importance for the subsequent development of the techniques of atmospheric exploration had been realized from the beginning of the 19th century.

Nevertheless, balloon work was started both at Annonay and Paris, by launching small balloons that were left to themselves, lost balloons as they were called, at the end of the 18th and through the 19th centuries. The lost balloon launched from the Champ de mars in 1783 three months before Charles’s ascent from the Tuileries was followed by telescope by the most famous astronomers of the time, who placed themselves on the highest points in Paris for the purpose of determining the horizontal projection of the balloon’s trajectory. The honour of making the first wind sounding is thus due to the astronomers. But it is surprising that was necessary to wait for nearly a century before anyone thought of employing systematically the lost balloon, referred to as a pilot balloon since the end of the 19th century, for the purpose of determining the speed and direction off the upper winds. This is all the more surprising in that every ascent by free manned balloon was preceded by the launching of lost balloons so as to inform aeronauts about the direction of the wind that furthermore, the inevitable item on the programme of all fairs held during the 19th century was the sending up of small balloons, frequently with cards attached. Neither Biot nor Gay-Lussac, nor Welsh, nor Glaisher not anybody else thought of making use of lost balloons for completing the results of their ascents. In 1879, Brissonet and Cassé launched a large number of small balloons provide with a return slip with a questionnaire and their address. Several of them were recovered great distances away and thus supplied interesting data about air currents. In 1881, Jobert and Silbermann reached the conclusion that, to be of use to science, lost balloons should carry instruments enabling the pressures attained and temperatures encountered to be ascertained at lest approximately but it is to Besançon and Hermite (nephew of the famous French mathematician) that the credit must be given for having succeeded in launching the first free balloon with measuring instruments. After several fruitless attempts, Hermite and Besançon managed on 8 September 1892, t launch a 2-cubmic metre paraffined paper balloon, weighing 20 grams with a maximum and minimum thermometer and a barometer consisting of a Vidie capsule, carrying a steel stylus which moved over a fixed glass slip coated with lampblack. The sounding balloon, which finally enabled the earth’s atmosphere to be systematically explored, had arrived. The following year, Hermit and Besançon made use of pressure and temperature recorders that Richard had just constructed. In order to reduce unnecessary weight, they used a single drum on which both temperature and pressure were recorded. This new device, called the barothermograph, soon became extensively used; it also had the advantage of ding away with the adjusting of the timing mechanisms of the two recorders. To complete the story, we must mention that Hermite and Besançon also had the idea of attaching an air sampler to several of their sounding balloons.

Assmann, inspired by the results obtained by Hermite and Besançon, made similar experiments. After a fruitless trial, he managed, in July 1894, t make a sounding up to a height of 17 km by means of a rubber-covered cotton balloon, the Cirrus, of 250 cubic metres capacity Thanks to the collaboration between aeronauts and meteorologists at the Deutsche Verein, sounding and manned balloons could be launched simultaneously, which enabled Assmann to check in vivo the working of the recorders carried by sounding balloons.

Initiation of an aerological network

Shortly after 1880, meteorologists realized the need for completing ground observations by those taken in the free atmosphere. The increasing interest shown in flying, which began at about the same time, was bound to favour the development of sounding techniques. The International Meteorological Committee, meeting at Uppsala in 1894, recognized the importance of manned and free balloons for studying the physics of the atmosphere. Two years later, in 1896, the MO Conference of Directors, held in Paris, agreed with the Committee’s views by creating the Commission for Aerology, which, with Hergesell as president, was requested to organize the exploration of the air by means of the sounding balloons used for the first time by Hermite and Besançon.

The first simultaneous international ascents of free and manned balloons organized by our commission were those of 14 November 1896 at Paris, Strasburg, Munch, Berlin Warsaw and St. Petersburg. Thus, 14 November 1896 the first International Aero logical Day. Up to the Second World War, our commission perseveringly and methodically continued to organize simultaneous international sounding campaigns. In this connection, we would recall the 1932-1933 Polar Year campaigns. The last one was that of the International Day of April 1939.

At its inception, 60 years ago, the aerological network thus included only 6 stations, stretching from Paris to St. Petersburg. A mere glance at the aerological charts that are now analysed daily by all meteorological services will show the progress that has been made sine 1896.

Discovery and exploration of the stratosphere

Under the enthusiastic leadership of its distinguished president the techniques of the pilot and sounding balloons made such rapid and remarkable progress that the beginning of the 20th century was marked by one of the most sensational discoveries that had ever been made in meteorology: that of the stratosphere by L. Teisserenc de Bort (1855-1913) and R. Assmann, in 1902. The former employed 100 cubic metre varnished paper balloons, whereas the latter made use of rubber balloons fro the first time. The rubber balloon ahs a distinct advantage over a paper or silk balloon, in that it has a practically constant rate of ascent up to the bursting point, thus affording better ventilation for the thermometers. Rubber balloons became much more generally employed, as it was possible to achieve a given height with a smaller balloon. The discovery of the stratosphere was a powerful stimulant; nearly all the national meteorological services set up an aerological section and sounding stations arose out of the ground as if by magic.

Exploring the atmosphere was not restricted to continents but also extended to oceans. Thanks to the generosity of Prince Albert of Monaco, who placed his yacht at Hergesell’s disposal, the latter was enabled from 1904 to 1906, to organize expeditions across the Atlantic Ocean to the arctic Seas and on the Mediterranean. In order to ascertain the place where the sonde fell and to recover it, Hergesell produced a device consisting of two balloons in tandem, the second acting as a parachute after the first pen had burst. Many followed his example, among whom Teisserenc de Bort and Rotch should be mentioned. Both of them confirmed Hergesell’s deductions about the stratosphere above the Atlantic and the circulation of trade winds.

It was due to the patient and persevering efforts of Teisserenc de Bort, Assmann and Hergesell, that aerology was enable to record the wonderful advance that we know today and fro which we reap the benefits.

J. Van Mieghem

4 June 1957

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