William Christopher Swinbank 1913-1973

Written by C.H.B. Priestley.

William Christopher Swinbank was born in Easington Village, Co. Durham, on 8 May 1913. His father was a mechanical engineer at a local coal mine, having started his career in the ship-building industry on the River Wear at Sunderland. His mother was a devout Catholic and through her faith he was brought up within the Catholic church, under some pressure from the local clergy that the brilliant youngster should be trained to enter the priesthood.

The pit-scarred landscape of his native county was a source of profound sorrow to him, in that nature had been exploited and the unsightly remains left to posterity. This and the extremes of the depression years caused the sensitive teenager to reject, permanently, all forms of establishment, the Church among them. The misery and the lame excuses were nourishment to a fiercely independent spirit and bred a life long hate of hypocrisy and humbug. But elements of his religious background remained strongly with him too: a refusal to compromise with principles as he saw them, and a good faith with his obligations even when he felt out of tune with the system which imposed them.

At the age of twelve he had obtained a scholarship to Henry Smith Grammar School at Hartlepool, where he was an outstanding student and a good athelete. He became captain of his house, the Spartans(!), as he used later to remind a fellow-member of that house, Dr Frank Pasquill, who was to match him in meteorological eminence. During these years he acquired a number of great and abiding loves, for the accurate use of the English language, for the classics and all that was best in science, for literature, and for music up to the generation before his own. Matching the man, there was special love for those with a strongly individual or humorously protesting style: Shakespeare of course, Robert Burns, L.F. Richardson in atmospheric science, Lewis Carroll, Oscar Wilde, Gilbert and Sullivan.

In 1931 he entered Hatfield College at Durham University where, over the heads of protests from senior lecturers who judged the task too heavy, he was allowed to take a special course in Double Honours in Physics and Mathematics. He graduated in 1934, but even for the top student, jobs were hard to get, and he stayed on a further year to take a teaching diploma. He taught physics at Windermere Grammar School and for a short period at Lewes, Sussex, Grammar School, and then worked as research physicist with Electrical and Mechanical Industries at Hayes, Middlesex. But neither teaching nor industrial research satisfied his restless and critical intelligence, and he took appointment as Technical Officer in the Meteorological Office, Air Ministry.

Weather forecasting remains today as a major and most difficult scientific challenge to the profession of physics. In 1938 it constituted an almost completely empirical exercise. Attached for forecasting duties to RAF stations, Swinbank came quickly to evaluate and respect the problems of synoptic-scale dynamics. But he struggled to find interest in the daily operational task. Tragedy, in the death of his young wife and infant child in separate hospitals in London, lost him all orientation for a while. Summoned to give evidence to an official enquiry into aircraft losses, he came out with characteristically frank but tactless comments on the state of the forecasting art. Officialdom, spurred apparently by the wise Ernest Gold, FRS, was to show both compassion and an unusual sense of fitness. In effect, it challenged him to see what he could do about it. At that time a main bugbear was fog, grounding vital air forces and endangering the landing of others. In an almost unprecedented step for the Meteorological Office of that era, this young scientist was transferred to head office for full-time study of the problem.

This was to be the real starting point of his career. In association with C.S. Durst, he began to develop in reasonable depth the scientific interests, notably in turbulence and atmospheric thermodynamics and cloud physics, which were to underlie many of his later contributions. Early in 1942 he moved to forecasting headquarters at Dunstable to continue his work on fog. There he met and married Angela Pinney, and from that time his star was in the ascendant.

It was towards the end of 1943 that I was posted to Dunstable to join Petterssen's group, and met Bill Swinbank for the first time. Petterssen and he had already collaborated in an important extension and application of Richardson's fundamental turbulence criterion. I had previously been concerned with the related problems of turbulent diffusion and, though preoccupied with operational requirements, we were among the few who liked to spend tea and coffee breaks discussing the science which lay behind. Another, P.A. Sheppard, has written on these times as follows:

There was a freshness and originality about Bill's physical thinking which was in the main very stimulating and a part of the fun was to distinguish his geese from his swans. One of his geese was the proposal to disperse fog by causing collision, coagulation and precipitation of fog droplets by the use of ultrasonics and some laboratory tests were undertaken to this end in the Physics Department at Imperial College (in collaboration with Mazur). Even though this idea came to nothing it led to some clarification of the energetics of fog.

He continued to wrestle with the fog prediction problem but spent part of his time in the upper-air analysis section which had recently been formed under Dr S. Petterssen. Weather systems and their associated (large-scale) motions had been of strong interest to Bill ever since his first operational assignment in the M.O. and he saw that any effective method of fog forecasting must be closely tied to the structure of the large-scale system in which fog might or might not form. However important the vertical transfer of heat and water vapour by (slow) turbulent diffusion may be in the production of fog, it would not, Bill saw, be by attempting to quantify this process directly that forecasting success would be likely to come at the time. He chose rather to study the relation of fog to bulk parameters of the weather system such as the hydrolapse (a term first used by WCS) between the earth's surface and the air immediately above the atmospheric boundary layer. He made a good deal of use in this study of captive-balloon sounding (BALTHUMS) to a km or so over Bedfordshire and was probably the first to show thereby how very sharp the changes of thermal and humidity gradient could be at the top of the atmospheric boundary layer.

Our whole energies were soon turned towards the development of upper air analysis and forecast techniques, and to their use for the fighting services. O.F.T. Roberts, F.A. Berson, and S. Petterssen had gone a long way to establish the superiority of isobaric (contour) analysis methods. It was Swinbank who thought most deeply about the energetics, through which we learnt how one chart was linked to its successor by the evolution, rather than simple advection, of the pattern of higher level temperatures or 'thickness lines'. The acid test of skill in meeting the new challenge was imminent. Some of the multiple air operations over Europe demanded precise routing and timing which had to be planned and executed from the forecast charts. These were projected forwards from analysis charts based, in turn, on data which was always inadequate and often non-existent over crucial areas. The six-hourly sounding network over the British Isles had revealed a meandering belt of westerly winds (later christened the jet stream) of strength hitherto quite unsuspected, augmenting the problems of forecasting and navigation from 15 000 ft upwards. Science can point to many examples of the important difference in meaning between precision and accuracy, and here was one on which many lives and even the fate of nations could well be depending. Imminent too was the participation of our unit in the most crucial forecast in history, which was later to be described in detail by J.M. Stagg in his book 'Forecast for Overlord: June 6, 1944'.

A year of intense operational pressure for the upper air group was to follow Overlord. One night we were on late duty together when, during a snatched tea-break, our discussion of turbulent transport of heat and other properties turned to the relative roles of buoyancy and shear-induced turbulence. Doubts about currently accepted thinking soon came to the fore, and in similar breaks over the next two days the essential evidence and implications were hammered out. Whether the resulting joint paper was the 'classic' which kinder friends have called it is arguable, but its novelty was not, nor the strength of the reaction by our seniors on the Meteorological Research Committee. This was to prove the most productive paper of our two careers, at least as measured by the mass of subsequent research which stemmed from it in one way or another.

No scientist could work with Swinbank for long without becoming aware of the depth and clarity of his physical insight and perception. His forte in thermodynamics was vital in understanding both the surface layers and the region (15 to 30 thousand feet) in which our official responsibilities then lay. I myself, initially a mathematician ever striving for stronger grasp of the physics of the atmosphere, gained more from my association with him than with any other, before or since. In 1946-7 I was most fortunate in gaining appointment to the CSIR with the challenge of developing a new activity in Australia, a research group in meteorological physics. Bill Swinbank was first choice for a colleague. Though we both knew that our two natures could never blend into an easy partnership, the challenge was equally attractive to him and our thus continued association was to endure longer than either could have foreseen.

Meanwhile, with the European peace, the demand for precise upper forecasts had slackened and Swinbank had returned to the problems of fog. Dunstable lay close to Harpenden (Rothamstead) and he was able to foster closer connection with the problems of agricultural physics, as they were then called, and notably with H.L. Penman. Years later Penman wrote:

I have known Mr Swinbank for more than 20 years, and in those preceding his departure for Australia the personal contact was close, and very rewarding for me. Our common interest was – and is – the study of the physics of the behaviour of the atmosphere near the ground, and I and my kind, in seeking agricultural and hydrological outlets for our work, have been very greatly dependent on Swinbank for ideas, experimental techniques, and scientific results.

Study of his impressive record of publication will show that he has produced all three in abundance. His ideas are invariably provocative, stimulating fresh thinking and new experiments; his new techniques have not been as frequently copied as they deserved, because few can match his skill in setting up and using apparatus; and his scientific results are gradually taking their place in the monographs and text-books of meteorological physics.

Most of his work has been done in Australia, in the Division of Meteorological Physics. This unit has an enviable world-wide reputation for the quality of its work, and no small part of the respect we outsiders have for it comes from what Swinbank has done himself or has inspired in his colleagues. In this context the Australian standard is the world standard, and Swinbank is one of those who has helped to make it so.

Arriving in Australia, Swinbank had the ball at his feet, employed by a liberal organization with no programme details yet committed, and with our common view that he would work best untrammelled. He had no responsibility -and at first did not seek any – other than to exploit the twin flairs for insight and experiment to which the above quotations have testified. Although in the instrumental arts he was not, in my opinion, quite the equal of our colleague E.L. Deacon, there was plenty of room for all in a subject whose underlying components were still so little investigated in other than ad hoc fashion. Micrometeorology was chosen as the first main theme for the group as a whole. We had brought a common interest in this field from England although there, with the exception of fog, the emphasis of previous work had lain in turbulent dispersion rather than in the geophysical context of air-surface interactions. Here in Australia the latter were far more intense. We considered them a set of poorly understood processes which underlay the climate, the water conservation, the primary industry of a whole continent. Research would have bearing on the way of life and on a multiplicity of other community problems ('environmental problems' according to their modern label). Within the main theme, Swinbank took to himself the target of measuring the vertical fluxes of heat, momentum and water-vapour (i.e. absolute measurement of evaporation), and with help along the road from Deacon, Taylor, McIlroy, Dyer, Webb, this work was to prove as successful as it was innovative, and it spun off, as foreseen, into a wealth of other basic and more applied results.

Through the formative years it was the basic micrometeorology and its applications into agricultural meteorology which mattered most. Since this work started scientists from some twenty countries (many of them developing ones) have been attracted to Aspendale for extended periods of collaborative research or advanced training, whilst the outgrowth of work of this type into other scientific institutions in Australia has been immense. As Penman has implied above, Swinbank was a principal architect of this situation but he did not, as many have supposed, initiate the effort in agricultural meteorology. Rather did he reject my suggestion that he should do so, preferring, with justification, to concentrate his own personal efforts on the more basic paths. He had produced a sensitive vapour pressure recorder which was developed further by McIlroy into a probe for general micro-fine measurement of temperature and humidity, while Angus went to work on frost protection in orchards. After these two had joined forces to study evaporation and other agricultural applications more systematically, Swinbank continued to be an interested contributor and critic. It is interesting to recall the recommendation of an early member of the Royal Society (was it Halley?) that the natural philosophers of his day should turn their attention to the weather-connected problems of the farmer, reasoning that should these efforts succeed the national welfare should benefit, whereas if they failed at least the time would have been spent in salubrious surroundings!

The direct measurement of the turbulent flux of any entity involves, in essence, the recording of the instantaneous departures from the average x' of the entity and simultaneously the instantaneous momentum component of the air normal to the surface, pw. The mean of the product of these two variables must then be evaluated. For the particularly difficult vertical momentum, Swinbank decided to adapt the hot wire anemometry techniques developed by L.F.G. Simmons for wind tunnel measurements. Hitherto our 'knowledge' of the three key geophysical fluxes, of sensible heat, water vapour (and hence latent heat), and horizontal momentum, and of the laws governing these, had rested on conjecture. Quite aside from instrumental challenges, the problem of measurement was far more simple to state than to achieve. There was no a priori knowledge of how finely the fluctuation structure needed to be resolved; that is, in physical terms, of the ranges of eddy sizes contributing to the various fluxes. The ranges themselves could be expected to vary with height, but in an unknown manner. How long a record was necessary for adequate averaging and for balancing of the energy budget had to be learnt the hard way. Again, the matching of response times for pw and x, and the question of removing the average pw, and the relevance of doing so, exposed hitherto unrealised problems and prompted much debate. An acceptable set of measurements was achieved in 1951, in time for the first International Symposium on Atmospheric Turbulence in the Boundary Layer, held at MIT later that year, a meeting which was the precursor of many which were to follow under various international auspices. A comment on this pioneering work makes interesting reading today. Professor Frenkiel's remark, 'you stopped at four hundred points (The number of points read off each 5-minute record), not for lack of data, but because it is such terrible computing work' was readily agreed. But the obvious follow-up suggestion, that the computation be automated ab initio, was one which we had considered and rejected. In fact it was from the individual fluctuation records, even more than from the flux statistics themselves, that much precious insight was to be gained over the next few years. Important internal properties of the turbulence, the variability of its character and not merely of its intensity, the very pronounced difference in character between fluctuations of the different entities x, which supported our claims for differences in transport mechanism, all these could well have been lost. Automation was achieved later (Dyer and Hicks) when the demand grew for eddy flux measurement in a number of more applied contexts.

By early 1953 Swinbank had completed, at Edithvale, a sufficiently large number of high quality flux measurements, and attention swung to the interpretive work so generously opened up. He himself stood somewhat aside from this. With his main objective achieved, he hankered for a more radical change of field. Studies of turbulent structure in themselves had never interested him greatly. I had suspected that some effects of buoyancy began to outweigh those of wind-shear turbulence at heights (and hence negative Richardson numbers) far smaller than had previously been thought. Free convection relationships appeared even with moderate winds. It was suggested that he might follow up this idea but he preferred otherwise, though long after its consolidation he returned to the issue and suggested new forms of dimensional analysis, which was one of his pet subjects.

All this was characteristic of the man and of his strong and interesting personality. He was no lone wolf, but he followed his own nose and had his own way of doing things, from which nobody could move him. Faced with a problem new to him he had to think it out for himself, going as far back into the grass-roots and the classics as he could manage, often deliberately ignoring much good recent work which had been done along the way. There were elements of arrogance and blindness in his attitude at times, and one came to learn that any critical or suggestive thought about his own work was best conveyed indirectly, so that absorption was unconscious. This is not an uncommon characteristic among research scientists who take pride in their independence of outlook. But uncommon indeed were his feeling for the atmosphere and his ability to get right to the heart of many of its complexities, stripping away the inessentials. Science needs its simplifiers side by side with its complicators, and he was the former par excellence. Many of his new ideas so produced were unorthodox but invariably, whether they stood the test of time or not, one found one had learnt something by pondering them.

These were among the qualities through which he contributed so greatly to the benefits of his environment and of his closest colleagues, though the same qualities at times could leave him somewhat oblivious of what he himself derived in return. He was a fine leader and guide to any younger scientist prepared to hearken to his precepts and to swallow his critical medicine.

Swinbank appreciated that the Edithvale work had turned the tables of the subject's development, that the fluxes had now been measured more accurately than the gradients and profiles which were necessary for the finer points of interpretation. By the standards of previous sites where temperature and wind profiles had been measured, Edithvale was superb. But still was it good enough for the ultimate baseline, strictly one-dimensional, situation without the solution of which the relevance of all further steps towards the resolution of nature's full complexity, e.g. advective and time-dependent situations, would suffer?

These ponderings were to bear fruit later. For some years his output of original work grew thinner, but they were years in which the Aspendale group greatly diversified its activities. In this diversification, he was a party to every main decision, an initiator of many, and a close and critical onlooker over the whole programme. For Berson's synoptic-dynamic group, even though this lay outside his personal responsibility, he supervised the development of a radar facility. He advocated that permanent ozone stations should be established in Australia and he guided the group leader, R.N. Kulkarni, in building up the network which, with the collaboration of the Bureau of Meteorology, has become the focus of work in the southern hemisphere. It has provided vital pointers to major differences between the two hemispheres in the general atmospheric circulation, particularly in the lower stratosphere, and will now provide a priceless backlog of data against which world climatic trends can be monitored in the light of changing aviation practices. He suggested the evaporation study of Lake Eucumbene, carried out by E.K. Webb in 1959, which was the first of its kind following that of Lake Meade in U.S.A., and established methodologies which have been generally used in subsequent lake studies in Australia. He gave impetus and guidance to the radiation group throughout its early years up to and beyond the premature death of its first leader, J.P. Funk. As he envisaged, this activity has now grown into a national observatory, a standards and calibration authority, an innovator of instruments and a strong research team in experimental and interpretive geophysics.

In this field too he made another characteristic contribution. Many had searched for satisfactory forms of parameterizing the downcoming infrared radiation from clear skies in terms of the temperature and water vapour content in the surface air. From the appreciation that there is generally enough vapour low down for its absorption bands to be virtually opaque, Swinbank argued that the temperature effect should be over-riding. This narrowed the search to a one-parameter function without, it was to be hoped, significant loss of accuracy. The idea was criticized as an oversimplification, but the results have stood up and have found use in many practical applications.

During this period he was also active in international work. He served on the International Ozone Commission, the International Joint Commission on Evaporation, and on WMO Working Groups on Atmospheric Ozone and on Plant Injury by Air Pollutants. At home, he was a Fellow of the Institute of Physics and a strong supporter of the Victorian Division, serving terms as committee-man and chairman, and representing the Australian Branch on the National UNESCO Committee for Natural Sciences. The Director of Meteorology, Dr W.J. Gibbs, writes:

Bill Swinbank had many good friends in the Bureau of Meteorology in spite of, or possibly because of, a somewhat abrupt and incisive attitude. Bill left one in no doubt if he considered an expression of views to be unscientific or illogical. As one got to know him better one found underneath the somewhat tough exterior lay a warm sympathetic personality. While many members of the Bureau will recall his always brief and to the point contributions to scientific discussions – sometimes devastating in their directness – they will also remember his willingness to assist those needing scientific advice and guidance. Members of the Bureau were, without exception, impressed by the depth and breadth of his scientific knowledge coupled with a thoroughly practical approach to real problems. Some of us had the advantage of getting to know him better at scientific conferences in Australia and overseas and found him charming, pleasant and witty company.

Some not so close to his actual work in meteorology were indeed put off by this apparent abruptness, and the width of his influence and of the impact of his work suffered in consequence. Outspoken when he wanted to be, much of the inner man was held back even from his intimates. His many-faceted character showed through in personal as well as professional idiosyncrasies. From the day he took up smoking he enjoyed a perpetual form of self-teasing in preparations to give it up, always buying cigarettes in the smallest packets or purchasing them one at a time from his colleagues. Many remember him at international airports, bowed down with only-just-portable radio or furnishing goods for his family, always pleased to have struck the best of all possible bargains. My own most vivid memory is of six weeks in Japan with a pair of skis he had bought for a colleague, carried into taxis, buses, trains, aircraft, blind to the inconvenience to himself and, unfortuantely, to his companions as well. His Spartan school influences had left their permanent impression. He would refuse a government car when travelling on interstate duty, rising at 5 a.m. to drive to Frankston Station whence by public transport, in three different stages, he would finally reach the airport.

The avoidance of inessentials and ornamentation was strongly reflected in the second period of his most productive research. The opening paragraph of his 1964 paper ran as follows: 'The central problem of micrometeorology concerns the shape of the wind profile when the air is thermally stratified, and may be formulated as follows. A steady wind blows over horizontal, uniform terrain and, in the general case, there will be an exchange of heat between the air and the underlying surface. Then it is required to determine the relationship which must exist between the wind shear delta-u_z/delta-z where u_z is the mean horizontal wind speed at the height z, the rate of vertical heat exchange per unit area H. the shearing stress exerted by the air on the surface and the height z itself. It seems unlikely that any other variable is relevant.' Here was the basic target focused in terms that few would challenge. But no adequate range of measurements with good fetch existed, and there was no physically mechanistic theory which predicted the variations of wind profile with heating or cooling from below. Nor could any of the derivative problems such as advection be really soundly formalized until the basic one had been resolved. Swinbank had spent thought, ahead of his contemporaries, in clarifying the stringent requirements on fetch and on steadiness of conditions which the baseline needs imposed. In 1960 he had formulated an attractive physical bridging hypothesis, of similarity type, from which the wind shear could be deduced as a function of height in a general and relatively simple exponential form. A sufficiently level and uniform site had been located at Kerang and a comprehensive set of measurements encompassing wind and temperature profiles, sensible heat, momentum flux and other energy quantities had been taken in February 1962. In 1963 and 1964, work continued at Kerang and at an equally good or even superior site at Hay. A.J. Dyer was the main collaborator; others, including overseas scientists, carried out adjunctive tasks. Measurements were extended to humidity profiles and evaporation and thus achieved coverage of the complete energy balance. For daytime (lapse) and slight inversion conditions, the quality of the informa-tion gained on these expeditions seems unlikely to be surpassed for many years. Indeed, it could be contended that the ultimate purpose has been served. With automation, Dyer and Hicks have subsequently supplemented it in important ways. Comparable work in moderate and strong inversions and over rough oceans constitutes the remaining experimental challenge. That the exponential profile did not survive the acid test was a source of disappointment to him as to his colleagues, even though we were all too well aware of Sir Harold Jeffreys' comment in the Earth: 'Turbulence in fluid motion, even in its simpler cases, is comparable in difficulty with nuclear physics. In the atmosphere we have all the problems of turbulence complicated by rotation and the proximity of a nearly spherical boundary.' It is one measure of the truth of Jeffreys' assertions that the profile of fluid flow over a boundary with heating from below, experimentally established by Swinbank, still awaits a satisfactory physical explanation.

The Hay-Kerang expeditions made history also in that they established a pattern, indeed a philosophy, for atmospheric field experiments on this scale. The literature contains many data tabulations of uneven quality, obtained with motives imprecisely defined, with easier but inessential measurements pushing out the harder essential ones. Swinbank aimed to do experiments in the real atmosphere which would rank in strength of focus and in precision with the great laboratory experiments of his classical idols. Preparation and subsequent scrutiny of each instrument and piece of data was unusually close, and any doubts on performance or on the realisation of the conditions laid down meant absolute rejection – for example, if the cloudiness changed during the course of a run. Each expedition had its specific hard-core content or limited primary objective. In one, emphasis might be on excellence in humidity profiles and vertical transfer (evaporation); in another, on dry conditions to allow extremes of lapse rate and sensible heat transfer to be studied; and so on. Progressively, the core group (Swinbank, Dyer, Stevenson, and assistants) were joined by other scientists and their assistants, anxious to make related measurements for whose interpretation the simultaneous baseline data would be invaluable. These were always welcome but Bill was the leader of the expedition. Others must arrange their programmes to phase in with his and, if they were not ready to go when conditions were right for the core group, they would miss out. Bill could be a martinet when he chose, and the proliferation of side-objectives, complexity of logistics and operation of Murphy's law (if anything can go wrong, it will), fully justified his single-mindedness as director on these occasions.

Within the Division at Aspendale, too, he took pains to enforce his authority, quietly but firmly and with generous sprinklings of sardonic wit. He was an able administrator, a quality deriving from his feeling for people, particularly the sub-professional staff, and his amazing memory: though this could be distorted by minor incidents which had either annoyed or amused him and could be stored up and reproduced years afterwards. To the staff of the Division he frequently filled the role of counsellor or trouble-shooter, and he gave unsparingly of his own time and trouble in listening to and advising those who brought their problems to him. His great sense of humour, which also could take a sharp twist, combined with a love of argument and strong views on science, politics, and society to make his company much sought after at the lunch table. He was never happier than when at the centre of things, organizing sing-songs at office parties or at home, accompanying on the mouth-organ and interspersing with the violin. Despite his independence it was very important to him to feel accepted by his colleagues, and he delighted in their companionship on informal occasions.

The same need also showed through strongly in his science. To him, as to many of us, recognition in science was an elixir. The Hay-Kerang work and its subsequent analysis earned him the 1968 Buchan Prize, the highest research award of the Royal Meteorological Society, in conjunction with Dyer. But possibly this, and certainly other high awards, came too late to make their most telling impact. The University of Durham awarded the DSc in 1973 after an earlier rejection, incomprehensible to his colleagues, had caused a discernible setback. That no physics body honoured this unusually able physicist was a frustration he shared with others whose work has lain in the near, as distinct from the remote, atmosphere. The Australian Academy of Science, slow to recognize excellence away from the traditional disciplines, elected him to Fellowship only in 1970. By this time, driven in part by lack of wider recognition here, he had gone on leave of absence to the National Center for Atmospheric Research in Boulder. In 1971 he resigned from CSIRO, where he had held the rank of Chief Research Scientist since 1961, in order to remain in Boulder as Director of the National Hail Research Experiment.

He had turned down many previous offers from the U.S.A. but had spent a number of terms there as visiting professor at Chicago and other universities. Paul Frenzen, friend for many years, who himself paid two extended visits to work at Aspendale, writes:

Bill was, of course, a truly gifted teacher. The courses in atmospheric turbulence and boundary layer phenomena which he taught at various times at the university of Hawaii, the University of California at Los Angeles, and Pennsylvania State University were uniformly successful. And from what he told me, I know these excursions in the academic world were for him particularly rewarding experiences. On several occasions he, with some pride, told me of the pleased reactions of his students to both the style and content of his presentations. I sometimes discussed the course material with him, it always being in the back of my mind to try to teach these subjects in order to learn them myself. In more recent years I frequently urged him to collect his turbulence course material in a monograph. Perhaps he had planned to do so, eventually.

Some of this material had been prepared originally for unit courses in Melbourne University which, to his chagrin, had been discontinued after two years.

At Boulder he was initially to be a member of the Advanced Study Program, to pursue his own special interests and to impinge on others where he chose. Even across the world, one could sense the continued mellowing. New colleagues and responses abounded, constraints which had grown irksome were replaced by different and, for a time, less burdensome ones: and with the assumption of the Directorship of the National Hail Research Experiment he began to enjoy the ultimate responsibility for which he had long yearned.

Dr. John Firor and Dr Chester Newton have generously supplied material for the account which follows:

The NHRE is aimed at the eventual modification of hail, but with strong emphasis on studies of the mechanisms of severe convective storms. These include the storm environment, the updraft velocity profile, radar reflectivity profile, liquid water content profile, conditions at cloud base, and atmospheric electricity. The possibility of modification derives from the consideration that size distribution depends on the concentration of freezing nuclei, that large hailstones should be suppressed by introducing artificial nuclei to compete for the supercooled water, thus producing a large number of much smaller stones.

Prior to 1971, there had been active negotiations on the need for such an experiment, to be funded nationally but drawing on the expertise and practical collaboration of numerous university groups. The qualities sought in the first Director had been defined. He must be able to deal with the many technical and scientific issues, have had experience in managing large and complex atmospheric field programmes and must deal effectively with the diverse scientific and support groups which needed to be brought together. It must have been a daunting prospect, especially to a man of Swinbank's simplifying predilections: to the arch-apostle of 'small science' and of the smaller field experiment designed to study one thing at a time. His acceptance of the challenge must, at the least, have put the brake on complexity, though this project could never be reduced to the Kerang-Hay denominator. Swinbank realised at once that the statistical results of seeding experiments would never be useful, possibly not even credible from the number of storms expected to be studied within the stipulated five-year period, unless supported by understanding of all the underlying physical processes. He shaped the characteristics of his core group, setting an example of long hours of hard work, facing them with a picture of a director who was very hard to convince, and requiring them to marshal their arguments and recommendations clearly and effectively. His chief colleague and lieutenant was Richard Sanborn who, at a memorial gathering held at Boulder shortly after Bill's death, and which drew a nation-wide attendance, said:

I remember his loyalty, his pride and the respect he had for the people who worked for him. He was one of those rare individuals who, by their own strength of character, was able to pull a diverse group together to work toward a common goal. I remember his love for a lively discussion with free exchange of ideas. How he encouraged us to think and challenge. And finally I remember that wonderful sense of humour.

And from Walter Orr Roberts, NCAR's first Director:

Bill was a great organizer, but no one knew better than he that organization charts and evaluation forms and the paraphernalia of management do little to assure success unless there is, first and foremost, dedication and a sense of involvement in getting things done that are worthwhile. The thing above all that Bill did for us was to keep us sane in the face of organized absurdity. I loved to watch his eyebrows during administrative meetings. They told more than thousands of words. And he didn't hesitate to pin-prick hypocrisy, which he enjoyed doing.

Swinbank was well aware of the practical difficulties which confronted the experiment, the inadequacy of knowledge of hailstorm circulations and cloud microphysical processes and the uncertainty as to the nature of the artificial nucleation process. In his representations to the sponsoring National Science Foundation he was noted for his clear descriptions of the physics of the problem, and for his candidness in telling precisely what had been accomplished and where lay the limitations in knowledge and practical expectation. The first practice year in the field had been held in 1971 and the project was scheduled for five subsequent summers of full operations. The incessant journeyings and the complexity of the responsibility must have taken their toll physically and, after apparently unidentified warning symptoms, he died of a heart attack on December 28 1973. He died at the moment when the project he had done so much to create was running well, with the major problems solved and prospects for three exceedingly effective years in the field. He also died shortly after having been selected as one of the first members in a newly created category called Senior Scientist at the National Center for Atmospheric Research, a group meant to encompass those few whose attainments and judgements should be recognized as the leaders of the National Center.

Happy as he was in America, Australia remained his home and he planned to retire to his house in Mount Eliza which he had considerably designed and built himself, with typical skill and care, in the days when life 'in the bush' still retained an element of pioneering. It had always been a pleasure to visit there. The charm and resource of his wife, Angela, supported him in his work and combined to form a bond of the closest possible mutual happiness. With their six children they built an unusually intimate family relationship which was a continuing source of pride to them.

The journal Boundary Layer Meteorology has honoured him with a memorial volume (1974), to which colleagues over the world have contributed papers and articles. One of special interest by Paul Frenzen supplements this memoir, quoting extensively from Swinbank's own writings to round out the full significance and surrounding philosophy of the exponential profile and the Hay-Kerang expeditions. It concludes by assigning Bill a place in the company described by one of his own special idols, James Clerk Maxwell:

There are only a few men who have stood in a similar position and who have been urged by the love of some truth, which they were confident was to be found though its form was as yet undefined, to devote themselves to minute observations and patient manual and mental toil in order to bring their thoughts into exact correspondence with things as they are.