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Jerome Namias
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Jerome Namias

Abstract

North Pacific sea surface temperature variations are analyzed as a result of and a controlling factor for the general atmospheric circulation during the period from May 1968 through the subsequent winter, when heavy rains in California, snows in Washington and Oregon, and disappearance of the Hawaiian trade winds occurred. The data indicate that a vast pool of abnormally warm water developed rapidly over southern portions of the North Pacific in June because of an abrupt May-to-June change in atmospheric circulation. This change favored strong subsidence in a deep Pacific anticyclone, dissipation of cloud, and greatly increased insolation. The climatologically stable Pacific anticyclone with its subsidence permitted the warm pool to remain through the subsequent fall. Penetration into the area of the pool by fronts and cold air masses during winter appears to have excited abnormal low-latitude cyclonic developments which transported deep moist air currents from the intertropical convergence zone into California. Gradually, the cyclones set into operation destructive factors which modified and later destroyed the warm pool.

The hypothesized air-sea coupling is documented with surface and upper air charts, ocean temperature data, satellite photos, and other material bearing on the study.

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JEROME NAMIAS

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JEROME NAMIAS

Abstract

Paths assumed by tropical cyclones in different fall seasons are related to the form of the prevailing mid-tropospheric general circulation. It is inferred that areas of vulnerability or invulnerability to these storms seem to be prescribed by the climatologically preferred circulation pattern during a given year, and for this reason expanded research along these lines could be highly rewarding. There is some indication that since the mid-thirties general circulation patterns have made east coast areas more vulnerable than during earlier years of the century.

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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

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New procedures are described for applying numerical methods to extended forecasting. These form a firm base which serves as a point of departure for the final forecast. The methods are sufficiently organized that training and actual forecasting are speeded up and the level of skill of prediction is higher than ever before.

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JEROME NAMIAS

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No Abstract Available.

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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

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

This paper constitutes an attempt to elucidate and account for the characteristics of persistence of mouth-to-month, season-to-season, and year-to-year midtropospheric flow patterns-patterns that control much of the weather and climate of North America.

The well-known signature of atmospheric forcing produced by normal seasonal factors is sharpened with new data, exposing a large residual of interannual variation to be documented and explained. In order to do this, several avenues are explored, including the preparation of statistics of pattern correlations stratified by month, season, year, and combinations thereof, as well as the stratification of data by quartiles representing high, low and intermediate persistence. Analyses of these data imply that certain flow patterns are more stable than others, and that the more stable patterns have stronger anomalies, are associated with mutually reinforcing teleconnections, and tend to be well reflected in persistent zonal wind speed profiles. Strong month-to-month persistence in the cold season accompanies or often precedes by a full year the mature stage of El Niño, thereby suggesting that a sustained anomalies atmospheric flow pattern helps instigate large tropical SST warmings.

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