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On the sea level pressure of the southern oscillation

  • T. N. Krishnamurti
  • Shao-Hang Chu
  • W. Iglesias
Article

Summary

In this paper an analysis of the sea level pressure on the time scale of the Southern Oscillation is carried out over the entire globe utilizing 16 years (1961–1976) of monthly mean sea level pressure. A special data collection based on numerous archives was used in this analysis effort. In addition, a Northern Hemisphere data set from the archives of the National Center for Atmospheric Research for 80 years of data (1900 to 1980) is also used in the present study. The major contribution here is an analysis of the antecedents of the major pressure reversals over the Indian Ocean and the eastern Pacific Ocean.

Four major El Niño episodes are covered by this study — 1965, 1969, 1972 and 1976. This study reveals a quasizonal two dimensional pressure anomaly pattern that exhibits both zonal and meridional propagation. In addition to the pressure fluctuations on the 2 to 6 year time scale this study places emphasis on a decadal time scale pressure oscillation which becomes apparent when the zonally averaged pressure anomalies are examined on a latitude-time section. The zonally averaged pressure anomalies appear to move from the south polar latitudes to the north polar latitudes during one decade and reversal of motion occurs in the ensuing decade. The calculations include sensitivity of the results to length of data records, width of time filter, space smoothing and data sets. Overall, the major results are shown to be substantiated. Our study clearly confirms the eastward motion of anomalies emphasized by Barnett. However, it is apparent that on the larger time span the evolution is more complicated.

A westerly wind anomaly over the western Pacific Ocean during El Niño years is also examined as a response of the boundary layer winds to the arrival of low frequency pressure anomalies.

Keywords

Southern Oscillation Decadal Time Scale Western Pacific Ocean Pressure Anomaly Eastern Pacific Ocean 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Über den Luftdruck der “Southern Oscillation” in Meeresniveau

Zusammenfassung

Diese Arbeit ist eine Analyse des Einflusses des Luftdrucks in Meeresniveau auf die Zeitskala der “Southern Oscillation”, wobei weltweit monatliche Luftdruckdaten aus 16 Jahren (1961–1976) verwendet wurden. Die Daten wurden für diese Untersuchung aus zahlreichen Archiven speziell zusammengetragen. Zusätzlich wurde ein Datensatz des “National Center of Atmospheric Research”, der Daten der Nordhalbkugel aus 80 Jahren (1900–1980) umfaßt, herangezogen. Das ermöglicht die Analyse von Anzeichen des Umschwenkens des Drucks über dem Indischen Ozean und dem Ostpazifik. Während des Untersuchungszeitraumes kam es zu vier „El Nino”-Episoden: 1965, 1969, 1972 und 1976. Diese Studie deckt eine quasizonale zweidimensionale Druckanomalie auf, die sowohl zonale als auch meridionale Ausbreitung zeigt. Es wird zusätzlich zu den Druckfluktuationen von 2 bis 6 Jahren auf eine zehnjährige Druckoszillation hingewiesen, die sich bei einer Breiten-Zeit-Analyse der zonal gemittelten Druckanomalien herausstellt. Die zonal gemittelten Druckanomalien scheinen sich in einer Dekade von antarktischen zu arktischen Breiten zu bewegen und vice versa in der folgenden Dekade. Die Berechnungen schließen Sensitivitätstests zur Länge der Zeitreihe, zur Weite des Zeitfilters, zur räumlichen Glättung und zu den verwendeten Datensätzen ein. Im großen kann gezeigt werden, daß die wichtigsten Ergebnisse substantiell sind. Unsere Studie bestätigt die von Barnett betonte Bewegung der Anomalien nach Osten deutlich. Es wird jedoch klar, daß die Entwicklung in einem größeren Zeitraum komplizierter ist. Ebenfalls wird eine Westwindanomalie über dem Westpazifik in El Niño-Jahren als Folge des Eintritts von niedrigfrequenten Druckanomalien auf den Wind in der Grenzschicht untersucht.

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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • T. N. Krishnamurti
    • 1
  • Shao-Hang Chu
    • 1
  • W. Iglesias
    • 1
  1. 1.Department of MeteorologyFlorida State UniversityTallahasseeUSA

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