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wave length given by the second of the earlier mentioned instability theories began to amplify and at the same time to act as a turbulent eddy in transferring its kinetic energy into the energy of the mean westerly flow. Westerly winds increasing with height were created at middle latitudes, and easterly surface winds developed in the extreme north and south. Thus the model exhibited both the typical phenomenon of cyclogenesis and the mechanism for transfer of energy into the westerlies. The flow thirty days after the asymmetric perturbation had begun to amplify bore a marked resemblance to the mean flow of the atmosphere. Further, the eddies which formed looked very like those that one observes in the atmosphere. The integrations also showed that a three-celled meridional circulation must exist in each hemisphere, with a thermally direct circulation in equatorial and polar regions and an indirect circulation in middle latitudes. The eddy gain of momentum by the upper atmosphere at middle latitudes is thus partially compensated by the action of the Coriolis force on the meridional circulations. As a result of these calculations, we now feel that the essential ingredients that make up the mean zonal circulation are far better understood. The next step in our program will be to introduce into our models topographical irregularities of the earth's surface, as well as a more realistic energy supply, in- cluding water vapor as a carrier of energy, to determine whether it is possible to explain the permanent perturbations of the atmosphere, i.e., to see whether one cannot construct a dynamic climatology. Only then, it is thought, will it be possible to deal with climatic anomalies and long-range prediction by numerico- dynamical means. Some preliminary investigations of the dynamical effects of topographic variation and heating indicate that the goal is not unattainable.

THE ROLE OF SYNOPTIC METEOROLOGY IN THE QUEST FOR OBJECTIVE WEA THER PREDICTION BY JEROME NAMIAS UNITED STATES WEATHER BUREAU Weather forecasting as practiced today employs a synoptic approach. The forecaster surveys a wealth of meteorological data which has been assembled simultaneously over large areas and analyzed in map form. The synoptic approach has been increasingly difficult in operation during the last twenty years, owing to the increase in data both at the surface and aloft which has made necessary a multiplicity of charts for obtaining a three-dimensional diagnosis of the atmosphere. The amount of information considered by the weather prognosticator has long since surpassed his digestive ability. Since the principal distinguishing character- istic of an outstanding weather forecaster is his ability to exercise proper weighting and judgment, it is no surprise that the multifold increase in data has not resulted in a proportionate increase in accuracy of forecasts. Although there have been great advances in meteorological knowledge, leading to specialized predictions of new weather elements and extending the time range of forecasts, it is difficult to prove that the basic weather forecast for the morrow has improved over the last half-century. Downloaded by guest on September 29, 2021 GEOPHYSICS: J. NAMIAS VOL. 41, 1955 803 This state of affairs, anomalous in the sense that increased knowledge has not led directly to improved prediction, is as frustrating to the present generation of meteorologists as it was to their predecessors. As a result of this frustration, groups of scientists in each of the last few decades have set out in a great quest for "objectivity"-a word that seems to take on special meaning for meteorologists. While forecasters are in complete agreement on the need for greater objectivity in weather prediction, they are, because of long exposure to highly touted but abortive attempts in the past, quite naturally cautious and conservative. One of the great breakthroughs in the attempt to give to forecasting the frame- work of organized knowledge was the Polar Front theory, pursued so vigorously in the 1920's. This development laid the groundwork for an analytical attack on weather-analytical in the sense of providing models of fronts and air masses for the cyclones and anticyclones of the weather map. While no one can deny the tremendous contribution made by the Scandinavians through the introduction of the Polar Front concept-and today it still forms the hard core of- synoptic analysis -it appears in retrospect that it still leaves too much room for imagination and human judgment to be considered an objective forecasting method. In the decade of the thirties a new dimension-the vertical-was unveiled before meteorologists, and for the first time reasonably complete maps could be prepared routinely for levels well removed from the surface, a great advance over having to make inferences from surface and cloud reports. The interpretation and exploita- tion of this upper-air data for forecasting purposes shortly became the principal concern of progressive meteorologists. Perhaps the tenor of the enthusiasm of the early thirties may be exemplified by the formal remarks of one of the now distin- guished pioneers of that period,' who wrote, "Probably the next ten years will see more real progress in weather forecasting than the last forty have seen." This prediction may be considered verified if the entire range of forecasts developed dur- ing the ensuing decade is surveyed. However, the improvement in 24- to 48-hour predictions would be difficult to demonstrate. Also in the 1930's, an objective attack was developed designed to predict the movements of fronts, cyclones and anticyclones, and other features of weather maps by kinematic methods.2 Since more than half the forecaster's stock in trade con- sists of moving weather systems along, this phase of his effort is certainly amenable to objective treatment. Although the elaborate kinematic methods developed in the 1930's for predicting the displacement of weather-map features are scarcely in evidence at forecast centers today, one cannot help wondering why this kinematic attack cannot be reinstituted with the help of high-speed computing machines. In this case the prognoses would not only be speedily available to the forecaster, but they would also include acceleration terms which he finds difficult to incorpo- rate. Besides, the very existence of an objective kinematic prognostic chart would eliminate a necessary pfiase of the forecaster's thinking and, in addition, would provide a comparison to serve as a control for more physically designed methods, which in any event should constitute the entree of the menu for elec- tronic computers. In the decade of the 1940's another innovation was made which in essence re- moved blinders from the meteorologist by increasing his horizon: this involved Downloaded by guest on September 29, 2021 804 GEOPHYSICS: J. NAMIAS PRoc. N. A. S. greater understanding of the hemispheric interdependence of weather phenomena. In this era a phenomenon of still larger scale than the cyclone and anticyclone, called the "planetary wave," was brought to light. These great horizontal un- dulations in the upper west-wind circulation provide a mechanism for great inter- changes of polar and tropical air and, in so doing, set the stage for cyclone and anticyclone formation and growth. While these general concepts now occupy a large share of the forecaster's thinking, attempts to make the reasoning more exact have not as yet succeeded in displacing imagination and judgment. Simultaneously with the planetary-wave attack on forecasting problems, there emerged a group of scientists dedicated to achieving complete objectivity, this time by statistical means. The originator of this approach was probably G. I. Taylor, who, in 1917,3 described a method in which the probability of occurrence or non- occurrence of fog could be assessed by plotting a diagram whose co-ordinates were air temperature and difference between wet and dry bulbs, the groupings of cases of fog or no fog at certain times falling into reasonably defined areas of the graph. In the 1940's this "scatter-diagram approach" was applied to a variety of meteor- ological prediction problems, including that of predicting for periods up to 72 hours in advance whether or not it would rain. In addition to being objective, this method supplied the user of the forecast with its probability of success. After a decade or so of this type of research, it has become clear that, while a surprising percentage of the human forecaster's skill is captured by the method, the plateau of skill reached is still remote from perfection. Perhaps more devastating is the fact that, being a purely statistical method, the approach offers no route of ascent once the plateau is reached. In view of these failures in the quest for objectivity over the last three decades, it is not surprising that the present crop of mature weather forecasters is not overly concerned about the possibility of technological unemployment through auto- mation. Yet they view with optimism the great forecasting experiments being conducted with electronic machines. This optimism in the face of past failures arises from certain significant differences from earlier attempts. These differences lie not so much in the underlying philosophy as in the scale of the attack. Thus the complex interdependence of planetary wave and cyclone wave along the polar front is taken into consideration by the use of physically based equations, and the true problem is not emasculated. These equations consider thousands of observa- tions-the problem that the human forecaster tries to cope with but must approach in an inexact manner by weighting factors from past experience, imagination, and scientifically based intuition. Thus the professional weather forecaster has some confidence in the current numerical attack because it does not ridiculously over- simplify his problems-and, in a sense, does not insult the Creator by assuming, as have some earlier-proposed methods, that a compressible fluid's secrets of behavior will emerge from two parameters plotted on a scatter diagram' Besides, the men currently employed in numerical forecasting work compose a nekv blend of dynamic and synoptic meteorologist, whereas theoreticians and practitioners have for years been lodged in separate camps. Statistically minded meteorologists also have cause for optimism, for modern electronic machines can empirically determine atmospheric interactions both simultaneously and with time lag with much greater Downloaded by guest on September 29, 2021 VOL. 41, 1955 GEOPHYSICS: J. NAMIAS 805 facility than by use of hammer-and-tong methods involving correlation and graph- ical approaches. While the prospect for objective forecasts is at least an order of magnitude brighter than ever before, it is doubtful that the role of the synoptic meteorologist will be abandoned or, for that matter, eclipsed for generations. In the first place, the primary requirement of a weather service is to produce a weather forecast. The relationship between air circulation, horizontal or vertical, and local weather is by no means unique and requires many more factors than can be handled con- veniently by present-day machines. While this deficiency may be partly overcome by better machines, the physics of small-scale effects may be of a higher order of difficulty than that of larger-scale effects. Perhaps the grid of observations neces- sary to define such local effects may be economically impossible to maintain. Here the experienced forecaster, assisted by statistics, might logically be able to give best interpretation to a larger-scale machine-produced prognosis. More important is the sobering fact that, while machine-produced prognoses of atmospheric circula- tion (prognostic charts) have been surprisingly good, considering the stage of the science, they still leave about half the real variability to be accounted for and show a disturbing tendency to approach the "plateau" of skill which has served as the burial ground for objective systems proposed in earlier years. In order to ascend from this plateau, and thus really to improve weather fore- casts, it would seem desirable that the experience and know-how of the synoptic meteorologist be fully utilized. To the extent that the dynamical equations gov- erning the behavior of the atmosphere are completely known, the errors of nu- merical prediction methods can be identified and thus eliminated. Yet the history of the development of weather forecasting has been so heavily weighted on the empirical side that it is conceivable that the experienced and well-trained fore- caster may be able to suggest avenues for improvement which theoreticians, be- cause of less complete knowledge of the real atmosphere, may overlook. Thus the role of the synoptic meteorologist in the era of numerical prediction may be just beginning! Until machine-made prognoses reach a level much higher than that presently achieved, it is clear that the final weather forecast must be issued by the profes- sional forecaster, using or discarding the guidance of information provided from any source. When complete and extensive verifying by statistics indicates that he is not bettering the machine-made product, it is time for him to branch out to a new field-perhaps long-range forecasting, where vivid imagination and scientific intuition are still predominant. Here his experience with a completely new class of motions which come into focus through time-averaged charts should be very helpful in formulating ideas for possible trial on high-speed computing machines. But, in contrast with the physical-dynamic attack on short-range forecasting problems, some compromise must be made to include statistics, at least until much more is known of the physics of the larger-scale, slower-moving phenomena brought to light by time averages. In fact, it is probable that, in attempts to work with phenomena of this scale with the help of computing machines, meteorologists will automatically learn more about their physics. It appears that the role of the synoptic meteorologist in the new era of high-speed Downloaded by guest on September 29, 2021 806 GEOPHYSICS: T. F. MALONE PROC. N. A. S.

computing machines is destined to be most contributory and rewarding. He will be the key individual in helping theoreticians to improve their short-range models by suggesting why and how initial ones went wrong; he will provide ideas for a numerical attack on long-range forecasting and will be indispensable for giving the most effective weatherwise interpretation of the machine-produced prognoses. 1 H. C. Willett, "The Use of Aerological Observations in Weather Forecasting," Trans. Am. Geophys. Union (15th annual meeting, April 26-28, 1934), Part I, pp. 7-10. 2 S. Petterssen, "Kinematic and Dynamical Properties of the Field of Pressure, with Application to Weather Forecasting," Geofys. Publikasjoner Norske Videnskaps-Akad. Oslo, Vol. 10, 1933. 3 G. I. Taylor, "The Formation of Fog and Mist," Quart. J. Roy. Meteorol. Soc., Vol. 43, 1917.

APPLICATION OF STATISTICAL METHODS IN WEATHER PREDICTION BY THOMAS F. MALONE* TRAVELERS WEATHER RESEARCH CENTER, HARTFORD, CONNECTICUT In weather prediction we are confronted with one of the most difficult scientific problems of our times. Moreover, viewed from the standpoint of the practicing forecaster, it is a problem which has not received the attention it merits. The translation of research results into field application has proceeded at what sometimes seems to be an agonizingly slow pace. Some of this can be explained by the very complexity of the problem we are trying to solve. We are working with an in- credibly complicated thermodynamic and hydrodynamic system of truly colossal proportions. The medium with which we are concerned is nonhomogeneous, com- pressible, turbulent, and inherently unstable, and it is strongly influenced by heat sources and sinks which are to a certain extent a function of the state of the system. The medium surrounds a rotating globe which constitutes a boundary whose char- acteristics are, also to a certain extent, determined by the state of the system. Basically, the problem is this: Given an initial state of this capricious and in- tricately interrelated hydrodynamic and thermodynamic system, how can a future state be predicted? In spite of the complexities listed above, and others which might be enumerated, reassuring progress is being made. Recent advances toward a better understand- ing of the hydrodynamical aspects of the problem, coupled with the development of high-speed computing equipment, promise to make the present era one of the most exciting in all meteorological history. Fortunate, indeed, are we who are working in this field in these times, and great is our responsibility to see that none of the tools and techniques of present-day science are overlooked in attempts to solve a problem which, if mastered, not only would be richly rewarding in per- sonal satisfaction but would also materially benefit our collective national econo- mies. What, then, does statistics have to offer that might be of value? It is with some diffidence that the present writer ventures an opinion, since he can claim no pro- fessional competence as a statistician and speaks only from the viewpoint of a synop- tic meteorologist who has experienced the singular and not infrequent frustrations Downloaded by guest on September 29, 2021