Interview With Professor E. H. Palmén
His investigations of selected cyclones date back to the years before the Second World War. During the war, Palmén was engaged in routine activities, and he embarked on a new scientific career just after the war, when, at the invitation of Carl-Gustaf Rossby, he went to the University of Chicago. At that time Rossby and his collaborators were carrying out research on the general circulation of the atmosphere, particularly jet streams, and Palmén's pioneer work in this area fitted in very well. In 1947 the Chicago group published a classic paper on the general circulation. Those who participated in this work were (in alphabetical order): Jule Charney, George Cressman, Dave Fultz, Seymour Hess, Alf Nyberg, Erik Palmén, Carl-Gustaf Rossby, Zdenek Sekera and Victor Starr. Professor Palmén remembers with mild resentment that, although his contribution to this work was indeed quite fundamental, his name was only mentioned along with Rossby's as project leader, Rossby's views being the dominant elements.
Perhaps one of the most important events in those days was Palmén's difference of opinion with Victor Starr (and members of the Chicago group). This gave rise to exchanges of correspondence between the two famous scientists with strong attacks and counter-attacks. It might be interesting here to recall a paragraph of Palmén's letter:
It is not clear whether the authors [Rossby and Starr] intended to question the necessity of meridional circulations for the maintenance of the kinetic energy of the atmosphere. Such an intention would mean a complete change of the whole foundation of dynamic meteorology, and I doubt strongly that the genius of the authors, recognized by all meteorologists, will be sufficient for that goal.
In his reply Starr said:
Apparently Palmén suspects me of highest heresy lest I suggest that the energy production process may also be accomplished without the aid of meridional circulation. This I have indeed proposed, and one outcome is reported by Dr. H. C. Willett in correspondence published in the preceding issue of this journal... Indeed if such are the fruits of heresy, then I say let us have more heresy... (Journal of Meteorology 6 (6) December 1949, pp. 429 and 430).
The investigations of the atmospheric jet streams led Palmén to further studies of energy conversions in the atmosphere. His work in connexion with the subtropical jet and the tropical circulation led to an interest in tropical cyclones, hurricanes and typhoons. Indeed, he showed why it is that tropical hurricanes form only in certain oceanic regions and only during certain seasons, the so-called hurricane season. In Palmén's opinion the reason was the thermal structure of the tropical atmosphere and its dependence on the surface temperature of the ocean. Later on, Palmén returned to the problem of the circulation of the atmosphere and worked out a satisfactory energy budget for the whole atmosphere.
Palmén has published more than 130 scientific papers. He has received the following awards: Symons Memorial Gold Medal (Royal Meteorological Society 1957), Carl-Gustaf Rossby Award (American Meteorological Society 1960), Buys Ballot Medal (Royal Netherlands Academy of Arts and Sciences 1964), Rossby Prize (Swedish Geophysical Society 1966), Silver Medal (Finnish Geophysical Society 1968), IMO Prize (WMO 1969).
He is a member of the following societies and academies: Societas Scientiarum Fennica (honorary member), Finnish Geographical Society (honorary member), Finnish Geophysical Society (honorary member), Swedish Geophysical Society (honorary member), American Meteorological Society (honorary member), New York Academy of Sciences (honorary life member), Royal Swedish Academy of Sciences (foreign member), Norwegian Academy of Science and Letters (foreign member), Royal Meteorological Society (foreign member), Leopoldine German Academy of Researchers in Natural Sciences (foreign member), Austrian Academy of Sciences (foreign member).
Erik Palmén is the perfect example of a gentleman. His elegant and soft-spoken manner and the way he treats his friends, and especially his students, has always been a source of encouragement. He appreciates good food and cigars.
The Editor of the WMO Bulletin was privileged to be accorded the following interview with Erik Palmén at the Department of Meteorology in the University of Helsinki on 4 November 1980. The last time he had seen Palmén was 20 years earlier on the occasion of his (the Editor's) final examination at the University of Stockholm.
We wish Erik Palmén many more years of happiness and success.
H.T. — What made you choose meteorology as a career?
E.P. — As a child I was very interested in meteorological phenomena. Already at the age of seven or eight I used to follow the movement of the clouds, changes in the weather and even made my own forecasts.
H.T. — Where did you start your meteorological studies?
E.P. — When I joined the University of Helsinki there was no possibility of taking a degree in meteorology, so my studies were mainly in the fields of astronomy, physics and mathematics. My Master's degree thesis was in astronomy.
H.T. — Who were your professors and your collaborators in those days?
E.P. — My professors were those who were engaged in teaching these subjects. However, in my main subject I was under the guidance of Professor Jacobus Sundman. He was a well-known international figure in the field of theoretical astronomy. At that time some lectures in meteorology were given by Professor Johansson. I attended some of these, even though, as I already said, I could not take a degree in meteorology.
H.T. — What was the status of the national Meteorological Service of Finland in those days?
E.P. — Because of the harsh winters and variable summers of the Finnish climate, nearly all the physics professors at the University during the last century were interested in observing climate and weather phenomena. Around 1850 the Office of Meteorology was founded under the auspices of the Finnish Society of Science, and this lasted until Finland became an independent country in 1917. The following year the Meteorological Office became a governmental institution. There was already quite a good network of meteorological stations in Finland at that time, as was the case in most other European countries.
H.T. — In 1923 you published your first scientific paper on the theory of cyclone tracks. What sort of data and information did you use for this study?
E. P. — In those days, of course, there were no regular synoptic upper-air observations. Therefore my first paper contained information based virtually entirely on surface observations. For this study I mostly used the synoptic maps which had been published in Russia covering the whole European region. The maps dated from before the First World War, since no more were available during the war, and we had to wait quite some time after the end of the war before similar data were obtainable again. I must emphasize that for this study I drew heavily on the results published by the famous Bergen school. I was already in contact with Tor Bergeron. His work impressed and influenced me enormously. Bergeron visited Finland several times and I benefited greatly from personal discussions with him.
H.T. — Who was the founder of the Bergen school? Who were your collaborators?
E. P. — The real founder of the Bergen school was Vilhelm Bjerknes, although he was not a synoptician. I had carefully studied the papers published by his son, J. Bjerknes as well as those by H. Solberg. Even before I met these scientists, I had the conviction that they had rendered a great service to synoptic meteorology and that theoretical knowledge had taken an important step forward.
H.T. — In 1922 you started to work at the Marine Research Institute at Helsinki. Which problems in oceanography interested you in particular?
E.P. — When I obtained my Master's degree from the University of Helsinki, the chief of this Institute, Professor Witting, offered me a post as assistant. Later on I became head of the section of the Institute which dealt with problems concerning water level changes, and finally I became Director of the Institute in 1939 and held that position until 1947. During that period I published several papers, most of which treated the relation between wind, wind stress and water level changes and the relation between winds and changes of stratification in the water, in the surface layer as well as at greater depths. My other publications dealt mainly with currents in the Baltic Sea and ice conditions in this area.
H.T. — Many of your papers relate to synoptic meteorology and you have been regarded by many eminent meteorologists as a pioneer of research in this field. Your studies were carried out when the data were no more than rudimentary. Did you find this exercise difficult or frustrating?
E.P. — A number of my papers were published before I had personal contact with the Bergen school. In 1928 I decided to visit Bergen. On my way through Oslo I met Professor Vilhelm Bjerknes who explained some of his ideas to me and asked me to go and stay with his son. During the two months I stayed in Bergen I was working in close collaboration with Jack Bjerknes and this collaboration continued up to the outbreak of the Second World War. My frequent visits to Bergen were in connexion with our collaboration in the field of synoptic upper-air investigations. No regular radiosonde observations existed in those days, and the only source of information from the upper air was balloons with meteorographs, pilot balloons and aircraft reports. Jack Bjerknes had already started observations using a small meteorograph constructed by the Belgian J. Jaumotte. Probably the most systematic and elaborate study was that conducted in 1935. At that time we wrote to a number of Meteorological Services in Europe asking them to make balloon observations at specific periods as soon as they received instructions from us by telegram. We waited until there seemed to be a typical cyclone (depression) moving from the Atlantic Ocean towards Europe. When we found a case which looked very favourable, we immediately informed all the European countries and asked them to proceed with making frequent balloon observations during the next two days. We were very lucky indeed since the depression in question, which formed over England, moved towards northern Europe and the Baltic Sea, developing into a mature cyclone. The European countries were very good in responding to our request; the synoptic aerological coverage was excellent for those days. The data enabled us to study not only the frontal surfaces but also stratospheric phenomena. It was most exciting to see that we were able to construct maps for different isobaric levels over practically the whole of Europe for a period of about two days.
H.T. — Where was Carl-Gustaf Rossby at that time, and where did you first meet him?
E.P. — The first time I met Rossby was in 1930 in Norway, when he visited Bergen. I had many fruitful discussions with him. I was impressed by his ability in meteorological research and his special talent for simplifying complicated theoretical problems. We met several times later on in Norway and Finland before the Second World War. Rossby was equally interested in oceanography, and he was in close collaboration with the Woods Hole Oceanographic Institute. The war brought a break in our contacts, but in 1941 he sent me a cable saying that he had become a professor at the University of Chicago and offering me a position. He wanted me to join him immediately. I could not accept, since as director of the Institute of Marine Research in Helsinki I was engaged in many activities and had numerous responsibilities during the war. After the war I found it rather difficult to carry on oceanographic research in Finland, particularly because we had lost our research vessel. About this time Rossby visited the USSR, and on his way back to the USA, he came to Finland. He again offered me the possibility of working with him in Chicago as visiting professor. This time I accepted, and left for Chicago in 1946 and stayed there for two years. After Rossby had left Chicago to take up his new position in Stockholm, I visited Chicago several times, and worked there for extended periods.
H. T. — Knowing both you and Rossby so well, I am sometimes surprised at your close friendship. You were a master in synoptic analysis and Rossby had little ability in analysing a map. Indeed, he was completely lost when given a chart and a pencil. How was it you got on so well together?
E.P. — We got on very well together because we were more or less the same age, had more or less the same background, and spoke the same language (Swedish). It is not true to say that Rossby was uninterested in synoptic meteorology. On the contrary, he showed great interest. In fact, I remember how Rossby used to collect all his collaborators at the University of Chicago and made them attend regular meteorological map discussions. It is true that Rossby did not analyse synoptic maps himself, but he had good analysts who did the work for him. Among others I should like to mention George Cressman, who at that time was an assistant in the Department of Meteorology at the University of Chicago. I consider those map discussions to have been extremely fruitful; I enjoyed them and learnt a great deal from them.
H.T. — You are considered by many meteorologists as the father of the jet stream. Your earlier papers on jet streams and their interrelation with the general circulation of the atmosphere and synoptic-scale disturbances are among the classical literature in meteorology. Was it difficult at that time to convince meteorologists of your theory?
E.P. — I can tell you a small anecdote here. We had already observed on several occasions very strong wind currents in the upper troposphere. In the autumn of 1946, when Solberg was visiting the University of Chicago to deliver a series of lectures about westerlies and the maximum anticyclonic wind shears that could be expected to exist in the upper levels, he affirmed that the maximum anticyclonic wind shear should correspond to the Coriolis parameter. I asked him whether he had verified his assumption from synoptic maps. His answer was 'Of course not. I am a theoretician, and I am not concerned with practical meteorology'. This led me to look seriously into the problem, so I sought out special cases with more or less westerly flows in the upper atmosphere. I found that if you have a strong flow in extratropical regions, it is practically always connected with a fairly pronounced polar front. In 1947 I presented such a special case during a discussion at the University of Chicago. I could show that the anticyclonic wind shear to the south of the core of the jet stream did in fact correspond to the Coriolis parameter. With the assistance of my students and collaborators, in particular K. M. Nagler and C. W. Newton, I then started to analyse several cases, and we came to the conclusion that the jet stream was actually a more or less global phenomenon, being weak in some places and strong in others. At that time I did not make any distinction between what later came to be called the polar-front jet and the subtropical jet. I remember I started to distinguish between them at about the time of a lecture which I gave in London at the Royal Meteorological Society — the Symons Memorial Lecture, and I presented the same idea in Berlin at a meteorological meeting. I was then convinced that the subtropical jet was more a tropical phenomenon related to the Hadley circulation.
H.T. — When did you start your investigations into transfer mechanisms in the general circulation of the atmosphere?
E.P. — I had studied a paper written by H. Jeffreys in 1926 pointing out the importance of the eddy transfer of angular momentum and heat in the atmosphere, but it was only in 1948 that my interest was aroused. I met Victor Starr at the University of Chicago and became acquainted with his studies of this problem. Right from the start I had some reservations about Starr's ideas since I felt that it was very difficult to have transport of angular momentum upwards in tropical zones without a strong Hadley circulation. We started something of a polemic about the importance of eddy transfer and transfer resulting from meridional circulations. In due course I came round to feeling that in many respects Starr was right, and that I should have accepted more of his ideas at the time. However, I am also convinced that in order to transfer angular momentum from the source region in the tropics to the extratropical zones, it is absolutely essential to have a relatively strong Hadley circulation.
H.T. — For how long did this disagreement between you and Starr last? Did this affect your personal relations with each other?
E.P. — Our personal relationship was always friendly. However, whenever I started a discussion, I had the feeling that Starr wanted to talk about different matters. I could not understand his attitude, but we never had any personal conflict. In retrospect it is clear that in many respects he was right and in some respects I was right.
H.T. — So when you started to discuss the problem, Starr changed the subject?
E.P. — Yes, he did. I don't know why. Probably this was due to his nature. He was often isolated, he did not frequently attend conferences or symposia. When he was at M. I. T. he stayed there practically all the time. He was in many ways a remarkable man, and his scientific contributions were of a very high standard.
H.T. — You did considerable work on tropical meteorology. How did you become interested in this area?
E.P. — The main reason was, of course, that at the University of Chicago I had close contact with Herbert Riehl who was and still is an eminent specialist in tropical meteorology. One day in 1947, I read in the newspapers that a strong cyclone was moving from east to west and was expected to hit the eastern coast of the United States of America. Being interested in seeing a tropical cyclone in real life I went to Boston, but unfortunately for me and fortunately for the inhabitants of the eastern seaboard, the hurricane crossed Florida and went towards the Caribbean Sea. I was so disappointed that when I returned to Chicago I decided to collect all the available data on that storm. I worked about 10 days and constructed a vertical cross-section through the hurricane when located over Florida. It was then that I started to think about the energy problem of tropical cyclones. I tried to find an interrelation between tropical cyclones and the sea-surface temperature, and came to the conclusion that hurricanes never formed in regions or at times when the sea-surface temperature does not reach at least 26° or 27°C. Then I related this to the temperature distribution in the upper troposphere and lower stratosphere and found that, in order to get positive development of kinetic energy, there must be a surface temperature of at least 26° or 27°C. When the temperature is lower, no kinetic energy can be produced. This result was accepted straight away by meteorologists; some of them, of course, had already been aware of this connexion between sea-surface and upper-air temperatures. Later on, Riehl and I made further investigations of the energy process in tropical cyclones. As regards the tropical circulation, I have already mentioned that I was interested in this problem in connexion with my work on the subtropical jet stream, and I was again convinced that a prerequisite for the existence of this jet was a strong Hadley circulation. My main work on the tropical circulation was done in 1953 and 1954 when I was at the University of California at Los Angeles. Here, with the help of Bjerknes and Mintz, I was able to compute the mean mass circulation in the northern tropical region during the winter season.
H.T. — You wrote a book together with Chester Newton. When did you start this work, and when did you finish it? Do you think that the book contains a record of your contribution to the understanding of synoptic meteorology and the general circulation of the atmosphere?
H.T. — In your opinion, what is the most significant development in the science of meteorology since the Second World War?
E.P. — Of course the most important developments in meteorology are the improvements in the observations and meteorological telecommunication system. The development of the radiosonde and other upper-air measuring systems has considerably improved the collection and accuracy of information. A vast quantity of data are obtained from all sorts of platforms from the Earth's surface to the outer limits of space. The processing of so much information would not be possible without modern computers. All sorts of mathematical models can be devised to simulate the behaviour of the atmosphere. Weather predictions four to five days ahead are common nowadays using these models, and the results are quite satisfactory. One by-product of this is that people are no longer interested in specific synoptic investigations since every special case is just a special case. There is also a tendency among local forecasters to rely too much on the numerical forecasts issued by large centres and not use their own judgement, since in this way they escape responsibility. That could well result in a decline in the accuracy of local forecasts.
H.T. — What sort of association did you have with IMO and WMO?
E. P. — As you know, the people who have had the strongest ties with IMO and the present WMO have mostly been connected with their national Meteorological Services. I never served at the Finnish Meteorological Institute. However, I was a member of the WMO Commission for Aerology simply because of my work between the wars in the field of synoptic aerology. For a short time I was a member of the WMO Commission for Marine Meteorology, largely on account of my previous work at the Institute of Marine Research. I also participated in several conferences organized by IMO and WMO.
H.T. — Were you pleased when you received the IMO Prize?
E.P. — I was indeed very pleased and I consider it a great honour. I must confess that I felt somewhat uneasy because my participation in WMO activities was not very great. In any case, being awarded the Prize was a big surprise to me since I was completely unaware that my name had been put forward.
H.T. — You are very modest when you say that you did not take part in the WMO activities. Your contributions to solving problems of the atmospheric general circulation, the energy and momentum budget, tropical meteorology, and so on, have advanced meteorological education and training a great deal, and since education and training is a major WMO programme, you have done more than your share. At all events, I am very happy to find you still so active and interested in the science. I am told that you spend most of your days at the University.
E.P. — My philosophy in life has been that most people are productive and come up with new ideas when they are young, even between the ages of 20 and 30. When they are between 30 and 40 they are often at their best. Between 40 and 60 one can still do a considerable amount of good work, but there are few people who can make substantial new contributions at the age of 60 or over. A good portion of my own life was scientifically unfruitful because of the war. However, after the war I was lucky to have contacts with an excellent group of younger scientists in the USA. The collaboration with the Bergen and Chicago schools were the best periods of my scientific life. Later on I spent a considerable amount of time finishing the book already referred to. Since I reached the age of 70, the science of meteorology has been advancing so fast that now all I can do is to try to follow the literature. From time to time I have discussions with young meteorologists at the University, and occasionally supervise some of their work. It is not good to be an old man, and, after all, what can you expect from somebody who is 82 years old?
H.T. — I believe that you have been, and still are, a lucky person. You have been able to enjoy the whole period of your life so far. I remember a friend of mine saying sadly that, as a young boy, whenever he wanted to discuss something with his father, his father told him that he was too young to understand. Now, when he tries to discuss problems with his children, they refuse to listen because they consider he is too old. He feels he has always been in the wrong period of life. Well, let us go on to my last question. You have a reputation, which is borne out by my experience, that you love to have a good life, good food and your cigars. How often do you go to a restaurant nowadays?
E.P. — At my age it is not really possible to enjoy good food any more. However, I am very dependent on my cigars and I smoke them regularly. As a young man I often felt that I had not enough force to start my work before I had lit a cigar.