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Jerome Namias
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Jerome Namias

The annual march of month-to-month persistence in anomaly of temperature, precipitation, and mid-tropospheric flow pattern over the United States is examined for approximately the past decade. The data indicate a tendency for persistence in all three elements during all adjacent pairs of months except from April to May and from October to November when great and often abrupt transitions of long period regimes occur. These empirical findings are related to a “self-developmental” hypothesis presented by the author in a recent paper and designed to explain the evolution of climatic anomalies. An analysis of the year-to-year behavior of persistence suggests possible gradual secular trends which might be related to sunspots, but the evidence is inconclusive. Finally, persistence is related to zonal index, and here there is a suggestion that during the colder parts of the year low index periods are more persistent than high.

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JEROME NAMIAS

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SOME METEOROLOGICAL ASPECTS OF DROUGHT

WITH SPECIAL REFERENCE TO THE SUMMERS OF 1952–54 OVER THE UNITED STATES

JEROME NAMIAS

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The problem of drought is examined as a manifestation of anomalous patterns of the atmosphere's general circulation. Special consideration is given to the quasi-stationary planetary wave ensembles which are responsible for extensive summertime drought over the United States. The critical importance of the great Atlantic and Pacific anticyclones for encouraging or discouraging the development of the great North American upper level anticyclone, the immediate drought producing cell, is emphasized.

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Jerome Namias
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AN INTRODUCTION TO THE STUDY OF AIR MASS ANALYSIS

Conditions of Atmospheric Stability; Lapse Rates

Jerome Namias
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Jerome Namias

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A 49-year time series of sea surface temperatures along the Peruvian coast is analyzed in order to find antecedent and subsequent indicators of El Niño (abnormally warm water) and its inverse. Precursory signs show up in certain statistics gathered seasons before the event, and these should be useful in forecasting the occurrence or non-occurrence of this economically important phenomenon.

The macroscale processes implied by the above data are explored with the help of Northern Hemisphere pressure patterns and geostrophic wind profiles. There is a strengthening of the North Pacific winter westerlies when El Niño occurs as suggested by Bjerknes, that is, through momentum transports from a variable Hadley cell. However, El Niño appears to be associated with an appreciably weakened Pacific High over the eastern third of the North Pacific during the preceding year. This lends support to the theory that generation of El Niño is a long-term large-scale process in which reduced wind strew permits an accelerated equatorial countercurrent and diminished equatorial upwelling.

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Jerome Namias

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An attempt is made to physically explain the distribution of lag correlations (with long-period trend removed) from one to four seasons based on 40 years of data at about 200 stations in the conterminous United States. These data are analysed with the help of histograms (and medians) for climatologically homogeneous areas and a series of isopleth charts. The results indicate that seasonal persistence is most pronounced 1) when summer is antecedent, 2) in most seasons along the West and East Coasts and near the Great Lakes, and 3) in areas and times where and when variability of snow cover or antecedent precipitation is large. Negative persistence occurs mainly between successive Springs and at certain seasons over the Western Plateau. Physical concepts involving heat storage and teleconnections from large-scale coupled air-sea systems over the North Pacific are suggested as causes. Unfortunately, the correlations are for the most part too small to be used as a sole guide for making long-range forecasts.

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JEROME NAMIAS

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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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JEROME NAMIAS

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No Abstract Available.

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