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Jerome Namias

Abstract

Seasonal mean sea surface temperatures and 1000–700 mb thicknesses are correlated by pattern and also for 5° squares over the eastern North Pacific in order to find out more about bulk heat exchange between ocean and atmosphere. The results bring out the importance of static stability as a primary variable in heat exchange—the stability being varied by air mass modifications associated with advection, by cyclonic and frontal lifting, and by heating or cooling of the mean surface. Geographical and temporal effects are described against this background.

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Jerome Namias

Abstract

This paper describes and partially explains the unusual development of an anomalous summer circulation and weather pattern in 1987 following a spring that had much different characteristics. Since the forecast for this pattern was successful, the main reasons for the evolution are detailed. Essentially, these involve the probable influences of factors associated with change in season (seasonal forcing) and some new ideas as to how to incorporate these changes objectively.

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Jerome Namias

Abstract

Some physical causes of United States drought are outlined. Among the associated factors is subsidence,either in the upper level anticyclones or to the south of strong jets, or sometimes under prevailing northerlycomponents of upper level flow. These conditions are engendered by abnormal forms of the atmosphere'sgeneral circulation. Causative factors vary in kind and degree according to area, so that droughts over theFar West differ from those of the Great Plains or the East. Examples of each of these are shown as well astreatment of a rapidly developing drought. It should be obvious from this report that a successful numerical(dynamical) solution of the drought problem should be high on meteorologists' agendas.

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Jerome Namias

Abstract

The oceanic and atmospheric anomalies of the winter of 1971–72, markedly different from those Prevailing during the 1960's, are described, analyzed, and subjected to experimental objective predictions. Sea-surface temperature patterns over the North Pacific developed in such a slow, orderly fashion from fall 1971 to the following winter that a kinematic treatment successfully captured the evolution. Physical processes associated with this evolution are investigated and show that local air-sea heat exchange played a negligible role relative to winter-mass transport around the North Pacific oceanic gyre.

The resulting winter sea-surface temperature pattern appeared to place demands on the overlying circulation, producing anomalous atmospheric flow patterns at sea level and aloft. A multiple-regression analysis based on 20 independent winters’ data was successfully used to predict the probable winter 1971–72 sea-level pressure pattern from the observed fall 1971 sea-surface temperature pattern. Finally the winter 1971–72 regime is considered as a break with the prevailing state of the winters since 1958, posing the unanswered question of whether a new climatic regime is emerging for the 1970's.

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Jerome Namias

Abstract

On the basis of accumulated aerological data on a hemisphere-wide scale, a reexamination is made of the problem of hemispheric zonal-index variations first raised in the late 1930's. These data lead to a theory explaining the important problem of how and why during each winter the zonal westerlies gradually fall to low strength and subsequently recover—the period of this “index cycle” consuming some four to six weeks. The theory postulates a mechanism for containment of air composing the polar and sub-polar cap by means of strong mid-troposphere westerlies created by large-scale confluence. In this manner cold air is produced and stored in northern latitudes, the atmospheric circulation operating as a vast condenser. The discharge of the condenser in the form of cold air outbreaks, long recognized as necessary for the atmospheric heat balance, is effected by a certain cellular-type blocking, which reaches maximum effectiveness in producing an extended index cycle only when the supply of abnormally cold air is abundant, usually in late February. The principal index cycles of the six years 1944 through 1949 serve as supporting evidence for the theory.

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PHYSICAL NATURE OF SOME FLUCTUATIONS IN THE SPEED OF THE ZONAL CIRCULATION

(Paper presented 27 December 1946 at the Annual Meeting, A.M.S., Cambridge, Massachusetts)

Jerome Namias

Abstract

New data are presented showing the interrelation of temperature and pressure fields in the mid-troposphere. This interrelation is sufficiently close to suggest a physical line of attack on the problem of fluctuations in the speed of the zonal circulation. A special case of frequent occurrence is described wherein increases in zonal speed result from large-scale confluence of cold and warm currents in mid-troposphere.

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Jerome Namias

Abstract

Stockholm's seasonal temperature averages, which are roughly representative of much of Scandinavia, are related to the regional and hemispheric tropospheric circulation. The special forms of the general circulation favoring cold winters and warm summers are investigated, leading to the conclusion that this area is uncommonly sensitive to the general hemispheric circulation. Furthermore, an attempt is made to show that there is some interdependence between the circulations favoring cold winters with the adjacent summer circulations, so that spells of years with increased continentality arise.

Further climatological aspects of variations of circulation and continentality are discussed.

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Jerome Namias

Abstract

No abstract available.

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Jerome Namias
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Jerome Namias

Harry Wexler was a close student of developing techniques in the field of long range forecasting, and a contributor to them, realizing that improvement of long range forecasts represents one of the most important goals of meteorology. His scientifically-oriented administrative ability played a large part in enlarging the role of this subject in the United States. Indeed, one of the principal reasons he pioneered in inaugurating the World Weather Watch program was to lay a firmer foundation for long-range forecasting. I was one of many who gained benefit and stimulation from a long friendship with him, and my lecture will recall some of the instances.

First, I want to describe the nature of the long range prediction problem as seen through the eyes of a pragmatist, and to present a balanced picture of what is now possible and what may become possible in the next decade or so. One might hope that this 10-year forecast of “weather predictability” will turn out better than a 10-year forecast of the weather itself!

Next, I will speak on the history of long range forecasting over the past century, as traced through the work of inventors of synoptic, statistical and physical approaches to the problem. In spite of decades of frustration imposed by lack of adequate data, ignorance of large-scale physical processes, and the absence of intensive and large-scale effort, meteorologists working on longe range problems have made encouraging progress.

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