Low-frequency Variations of the Zonal Mean State of the Southern Hemisphere Troposphere

Shiotani, Masato

doi:10.2151/jmsj1965.68.4_461

Cited by 38 publications

(25 citation statements)

References 24 publications

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“…This is in agreement with the work of Shiotani (1990), who showed that, on seasonal time scales, when geopotential heights at high latitude are low and the split jet is pronounced, transient eddy activity near the Antarctic coast is vigorous near the Ross Ice Shelf.…”

Section: The Split Jet Region Of the Western Pacificsupporting

confidence: 93%

The El Niño–southern oscillation and Antarctica

Turner

2004

Intl Journal of Climatology

448

430

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This paper reviews our understanding of how the effects of the El Niño-southern oscillation (ENSO) might be transmitted from the tropical Pacific Ocean to the Antarctic, and examines the evidence for such signals in the Antarctic meteorological, sea ice, ice core and biological records. Many scientific disciples concerned with the Antarctic require an understanding of how the climatic conditions in the tropical and mid-latitude regions affect the Antarctic, and it is hoped that this review will aid their work.The most pronounced signals of ENSO are found over the southeast Pacific as a result of a climatological Rossby wave train that gives positive (negative) height anomalies over the Amundsen-Bellingshausen Sea during El Niño (La Niña) events. However, the extra-tropical signature can sometimes show a high degree of variability between events in this area. In West Antarctica, links between ENSO and precipitation have shown variability on the decadal time scale. Across the continent itself, it is even more difficult to relate meteorological conditions to ENSO, yet analyses of the long meteorological records from the stations do indicate a distinct switch in sign of the pressure anomalies from positive to negative across the minimum in the southern oscillation index.The oceanic signals of ENSO around the Antarctic are less clear, but it has been suggested that the Antarctic circumpolar wave could be forced by the phenomenon.Ice-core data offer the potential to help in understanding the long-term relationship between ENSO and the climate of the Antarctic, but there are difficulties because of the need to smooth the ice-core data to overcome the mixing of snow on the surface. Nevertheless, analysis of methylsulphonic acid in a South Pole core has shown high variability on ENSO time scales.It is clear that some evidence of ENSO can be found in the Antarctic meteorological and ice-core records; however, many of the relationships tend not to be stable with time, and we currently have a poor understanding of the transfer functions by which such signals arrive at the Antarctic from the tropical Pacific.

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Section: The Split Jet Region Of the Western Pacificsupporting

confidence: 93%

The El Niño–southern oscillation and Antarctica

Turner

2004

Intl Journal of Climatology

448

430

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“…Elsewhere in West Antarctica the impact of this event was manifested as a significant reduction in precipitation, whereas in 1989, another warm AP winter (but ENSO cold event), there was an increase in precipitation [Cullather et al, 1996]. Work by Shiotani [1990] identified a significant circulation change during the 1983 winter, with a switch from positive (negative) 1000 hPa height anomalies at high (low) latitudes to the converse, taking place between 25 June and 27 July. The daily temperature record from Faraday indicates that this change probably occurred at the beginning of July, when temperatures showed a marked decrease before rapidly recovering to mean values higher than those in June.…”

Section: Resultsmentioning

confidence: 99%

Southern hemisphere circulation anomalies associated with extreme Antarctic peninsula winter temperatures

Marshall

King

1998

Geophysical Research Letters

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“…The variability of Southern Hemisphere (SH) atmospheric circulation is dominated by an approximately zonally symmetric pattern, referred to as the southern annular mode (SAM), characterized by a dipole in the zonal wind strength with opposing centers of action near 408 and 658S and an equivalent barotropic structure in the vertical (Kidson 1988;Karoly 1990;Shiotani 1990;Hartmann and Lo 1998;Feldstein and Lee 1998;Limpasuvan and Hartmann 2000;Thompson and Wallace 2000;Lorenz and Hartmann 2001;Vallis et al 2004;Rashid and Simmonds 2004). The SAM, which accounts for 20%-30% of the total monthly sea level pressure (SLP) or geopotential height variability south of 208S (Thompson and Wallace 2000), was previously referred to as the ''high-latitude mode'' (e.g., Karoly 1990;Kidson 1999) and the ''Antarctic Oscillation (AAO)'' (Thompson and Wallace 2000).…”

Section: Introductionmentioning

confidence: 99%

Influence of the Tropics on the Southern Annular Mode

et al. 2012

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Perturbations in the southern annular mode (SAM) are shown to be significantly correlated with SST anomalies in the central tropical Pacific during austral winter and SST anomalies in the eastern tropical Pacific during austral summer. The SAM signature in the Pacific sector resembles a tropically forced Rossby wave train, the so-called Pacific-South American pattern, while the signature in the Indian Ocean sector is a zonally elongated meridional dipole. Thus, the SAM contains strong zonally asymmetric variability and tends to behave differently in the Eastern and Western Hemispheres, with internal dynamics prevailing in the Indian Ocean sector and the forced response to tropical SST anomalies exerting a strong influence in the Pacific sector. The tropically forced component of the SAM in the Pacific sector is related to a geographically fixed active Rossby wave source to the east of Australia within the core of the subtropical jet. In addition to the well-documented positive trend in summer, the SAM also exhibits a negative wintertime trend since 1979, characterized by prominent geopotential height increases over the high latitudes. In both seasons, SAM trends are closely linked to long-term trends in tropical Pacific SST that are independent of the canonical eastern Pacific ENSO variability. Although the SAM is an intrinsic pattern of high-latitude variability, the SAM index reflects the superposition of both high-latitude and tropically forced variability.

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Low-frequency Variations of the Zonal Mean State of the Southern Hemisphere Troposphere

Cited by 38 publications

References 24 publications

The El Niño–southern oscillation and Antarctica

The El Niño–southern oscillation and Antarctica

Southern hemisphere circulation anomalies associated with extreme Antarctic peninsula winter temperatures

Influence of the Tropics on the Southern Annular Mode

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