ALBERT

Description: The following report is presented as a statement of progress made at the Massachusetts Institute of Technology (M.I.T.) in the investigation into the possibility of extending the range of reliable weather forecasts. This project has been supported at M.I.T. and other private institutions by Bankhead-Jones appropriations since September, 1937. This report is concerned only with the work completed or in progress at M.I.T. The complementary program now in progress at the Weather Bureau in Washington is referred to only in so far as it has contributed directly to these investigations. Furthermore, the following report refers only to the last two years of the M.I.T. project. The first year of the three-year project was given over principally to the study of the results obtained by long range forecast methods already in use, and to the establishment of a northern hemisphere synoptic weather map procedure as a necessary precedent to the preparation of weekly forecasts on a synoptic basis. The results of the M.I.T. study of certain long range forecast methods already in practice are included in a general survey of such methods already published. The synoptic charts prepared at M.I.T. during that first year of the investigation are listed in an appendix to this report, together with those of the last two years. The preparation of weekly forecasts carried on during a part of that first year was so experimental in nature, and the procedure was so much changed the following year, that the results obtained were considered neither suffciently significant nor comparable enough with the later forecast results to merit any discussion. The present report is divided into three principal sections. Section I presents in condensed form our present conception of the essential nature of the general circulation, and discusses briefly the background of one or two of Professor Rossby's theoretical considerations concerning the general circulation which have found statistical and synoptic application in this investigation. Section II contains in brief form the results of synoptic and statistical checks of a large number of hypothetical relationships which might be assumed to hold in the earth's atmosphere. These include possible relationships in the large scale features of the general circulation, relationships between the general circulation and its different branches or centers of action, between the different branches or centers of action of the general circulation, between characteristics of the general circulation or its branches and anomalies of the meteorological elements in certain regions, between anomalies of the meteorological elements in one region and those in another region, and even between solar activity (sunspots) and characteristics of the general circulation or anomalies of the meteorological elements. The aim was to investigate possible interrelationships of all kinds, either with or without lag, in order to detect as many interaction principles or points as possible in the earth's atmosphere, whether they had direct or only the most indirect bearing on the forecast problem. The relationships investigated applied to daily, weekly, monthly, seasonal, or annual mean conditions. They were selected for investigation either from theoretical or practical considerations of the nature of the general circulation as outlined in Section I, or on the basis of popular beliefs which have long been current among meteorologists, or on the basis of direct observation of data which looked promising. The majority of these hypothetical relationships are found to be quite weak when subjected to rigid statistical checks, but all such results, whether positive or negative, are summarized in this report. Section III outlines the five-day forecast routine practice which has been carried on at M.I.T. during the greater part of the past two years on a weekly basis. It includes a statistical analysis of the verification results. In the conclusion are summarized the results of the investigation which thus far appear significant enough to justify their consideration in five-day or longer range forecasts. Suggestions are offered as to further steps which might profitably be taken if the investigation is to be continued. Finally there is an appendix in which are listed all the daily synoptic maps and mean charts and diagrams of surface and upper air data which have been plotted and analyzed at M.I.T. in connection with this project during the past three years. The importance of such a list is apparent when it is realized that inevitably in an investigation of this kind much the greater part of the time and effort expended is consumed in the routine or semiroutine duties involved in the preparation of such charts.

Description: The present report is intended to cover fully the activities of the long-range forecast project both at the Massachusetts Institute of Technology and at the U. S. Weather Bureau in Washington, between July 1, 1940, and August 1, 1941. It includes all material bearing on the activities of the current fiscal year which has appeared in the three progress reports that were written during the year. The report is in four sections. Section I outlines the administrative set-up of the project and its transfer from the Massachusetts Institute of Technology to the U. S. Weather Bureau in Washington, indicates the general purpose of the project, outlines the program of routine synoptic and statistical work which is maintained as a necessary part of the five-day forecast service, and lists the personnel which has been available to carry on the project. Section II covers in some detail the five-day forecast procedure as practiced during the past year, including one illustrative case selected and discussed by Mr. Namias. The discussion of the five-day forecast procedure is concluded with some remarks on the significance of the results obtained by the basic method and a summary by Mr. Allen of the success of the forecasts as shown by the statistical verification of the forecast temperature and precipitation anomalies. Section III contains a brief discussion of each of the special investigations made during the past year which bear on the five-day forecast problem. For the most part, the results of these investigations were not obtained soon enough to be incorporated in the forecast procedure outlined in Section II. Section IV sets forth recommendations for further theoretical, synoptic and statistical research which is needed to develop and extend the five-day forecasting technique which has been developed by this project.

Description: A. On the maintenance of the westerlies south of the polar front. B. Technique and examples of isentropic analysis. C. Isentropic analysis of a case of anticyclogenesis.

Description: This paper constitutes Part I of a report on certain investigations which have been in progress at the Massachusetts Institute of Technology during the past few years and which have been supported in part with funds provided by the Weather Bureau of the U. S. Department of Agriculture under the Bankhead-Jones Special Research Fund. The ultimate purpose of these investigations is to develop a sound physical model of the general circulation of the atmosphere, in the hope that an improved understanding of this process eventually may furnish valuable clues as to how the time range of our present daily weather forecasts may be extended and their quality be improved. In the past, the interpretation of the large-scale circulations of the atmosphere with the aid of the tools of classical hydrodynamics has suffered from the fact that these tools were designed for the study of thermodynamically inactive fluids, in which, furthermore, viscous or eddy stresses could be neglected. Through the work of V. Bjerknes and his students a good start has now been made towards the development of a science of hydrodynamics applicable also to thermodynamically active fluids, in which density changes are taking place as a result of non-adiabatic temperature changes. The removal of the second restriction-i.e., the development of hydrodynamic tools adapted to the study of fluids in which eddy stresses playa dominant role-has been accomplished mainly through the investigations of the Göttingen school of fluid mechanics. As yet, no synthesis of these two modern developments has been accomplished, although it is becoming increasingly clear that such a synthesis is needed before any headway can be made with the interpretation of the behaviour of the atmosphere. There has been a tendency on the part of meteorologists to assume that the effects of eddy stresses are restricted to a layer near the ground, and that the atmosphere above this layer behaves approximately as an ideal fluid. Even fairly elementary considerations show that a real understanding of atmospheric circulations becomes absolutely impossible on the basis of this assumption. A modest first attempt towards such a synthesis of the Norwegian and German developments will be attempted in these reports. It will be shown that the movements in the free atmosphere above the ground friction layer are affected by large-scale lateral mixing processes which produce shearing stresses acting across vertical planes, and one or two examples will be given to demonstrate that reasonable steady state solutions for the atmosphere can be obtained by taking this internal stress distribution into account. It will be shown, moreover, that the distribution of cold sources and heat sources in the free atmosphere is at least in part controlled by the stress distribution, which regúlates the location of ascending and descending movements.