El Niño–Southern Oscillation diversity and Southern Africa teleconnections during Austral Summer

2014 ◽  
Vol 45 (5-6) ◽  
pp. 1583-1599 ◽  
Author(s):  
Andrew Hoell ◽  
Chris Funk ◽  
Tamuka Magadzire ◽  
Jens Zinke ◽  
Greg Husak
Keyword(s):  
Southern Africa ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Austral Summer ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation

Observed Relationships between the El Niño–Southern Oscillation and the Extratropical Zonal-Mean Circulation

2006 ◽  
Vol 19 (2) ◽  
pp. 276-287 ◽  
Author(s):  
Michelle L. L’Heureux ◽  
David W. J. Thompson
Keyword(s):  
Zonal Wind ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Austral Summer ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Annular Mode ◽  
Mean Circulation ◽  
The Impact

Abstract There is increasing evidence indicating that the climate response to variations in the El Niño–Southern Oscillation (ENSO) includes not only thermally forced zonal wind anomalies in the subtropics but also eddy-driven zonal wind anomalies that extend into the mid–high latitudes of both hemispheres. In this study, new insights into the observed seasonally varying signature of ENSO in the extratropical zonal-mean circulation are provided and the associated linkages with the dominant patterns of extratropical variability are examined. The zonal-mean extratropical atmospheric response to ENSO is characterized by two principal features: an equivalent barotropic dipole in the Southern Hemisphere (SH) zonal-mean zonal flow with centers of action located near ∼40° and ∼60° during austral summer, and a weaker, but analogous, dipole in the Northern Hemisphere (NH) with centers of action located near ∼25° and ∼45° during early and late boreal winter. Both structures are accompanied by eddy momentum flux anomalies that exhibit a remarkable degree of hemispheric symmetry. In the SH, the extratropical signature of ENSO projects strongly onto the primary mode of large-scale variability, the southern annular mode (SAM). During the austral summer, roughly 25% of the temporal variability in the SAM is linearly related to fluctuations in the ENSO cycle. An analogous relationship is not observed in association with the principal mode of climate variability in the NH, the northern annular mode (NAM). It is argued that the seasonally varying impact of ENSO on the extratropical circulation is consistent with the impact of the thermally forced subtropical wind anomalies on the dissipation of equatorward-propagating wave activity at subtropical latitudes.

scholarly journals Relationships between the El-Niño Southern Oscillation and spate flows in southern Africa and Australia

2004 ◽  
Vol 8 (6) ◽  
pp. 1118-1128 ◽  
Author(s):  
J. P. Whiting ◽  
M. F. Lambert ◽  
A. V. Metcalfe ◽  
P. T. Adamson ◽  
S. W. Franks ◽  
...  
Keyword(s):  
Southern Africa ◽  
El Niño ◽  
Arid Zone ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Arid Zones ◽  
Interdecadal Pacific Oscillation ◽  
Discrete Flow

Abstract. The flow records of arid zone rivers are characterised by a high degree of seasonal variability, being dominated by long periods of very low or zero flow. Discrete flow events in these rivers are influenced by aseasonal factors such as global climate forcings. The atmospheric circulations of the El-Niño Southern Oscillation (ENSO) have been shown to influence climate regimes across many parts of the world. Strong teleconnections between changing ENSO regimes and discharges are likely to be observed in highly variable arid zones. In this paper, the influence of ENSO mechanisms on the flow records of two arid zone rivers in each of Australia and Southern Africa are identified. ENSO signals, together with multi-decadal variability in their impact as identified through seasonal values of the Interdecadal Pacific Oscillation (IPO) index, are shown to influence both the rate of occurrence and the size of discrete flow episodes in these rivers. Keywords: arid zones, streamflow, spates, climate variability, ENSO, Interdecadal Pacific Oscillation, IPO

Non–ENSO control on southern Africa precipitation variability

2005 ◽  
Vol 363 (1826) ◽  
pp. 61-62 ◽  
Author(s):  
Gil Lizcano ◽  
Martin Todd
Keyword(s):  
Southern Africa ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Precipitation Variability ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Composite Analysis

The objective of this study is to quantify the nature of the mechanisms of southern Africa rainfall variability, unrelated to the El Niño Southern Oscillation, by means of a simple empirical composite analysis, as a baseline for a more detailed study.

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