scholarly journals Potential Sources of Decadal Climate Variability over Southern Africa

2015 ◽  
Vol 28 (22) ◽  
pp. 8695-8709 ◽  
Author(s):  
Yushi Morioka ◽  
Francois Engelbrecht ◽  
Swadhin K. Behera
Keyword(s):  
Indian Ocean ◽  
Climate Variability ◽  
Southern Africa ◽  
South Atlantic ◽  
Decadal Climate Variability ◽  
The South ◽  
Sst Anomaly ◽  
Decadal Climate ◽  
Southwestern Indian Ocean ◽  
Sst Anomalies

Abstract Potential sources of decadal climate variability over southern Africa are examined by conducting in-depth analysis of available datasets and coupled general circulation model (CGCM) experiments. The observational data in recent decades show a bidecadal variability noticeable in the southern African rainfall with its positive phase of peak during 1999/2000. It is found that the rainfall variability is related to anomalous moisture advection from the southwestern Indian Ocean, where the anomalous sea level pressure (SLP) develops. The SLP anomaly is accompanied by anomalous sea surface temperature (SST). Both SLP and SST anomalies slowly propagate eastward from the South Atlantic to the southwestern Indian Ocean. The analysis of mixed layer temperature tendency reveals that the SST anomaly in the southwestern Indian Ocean is mainly due to eastward advection of the SST anomaly by the Antarctic Circumpolar Current. The eastward propagation of SLP and SST anomalies are also confirmed in the 270-yr outputs of the CGCM control experiment. However, in a sensitivity experiment where the SST anomalies in the South Atlantic are suppressed by the model climatology, the eastward propagation of the SLP anomaly from the South Atlantic disappears. These results suggest that the local air–sea coupling in the South Atlantic may be important for the eastward propagation of the SLP anomaly from the South Atlantic to the southwestern Indian Ocean. Although remote influences from the tropical Pacific and Antarctica were widely discussed, this study provides new evidence for the potential role of local air–sea coupling in the South Atlantic for the decadal climate variability over southern Africa.

scholarly journals Interdecadal-decadal climate variability from multicoral oxygen isotope records in the South Pacific Convergence Zone region since 1650 A.D.

2008 ◽  
Vol 23 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
Braddock K. Linsley ◽  
Peipei Zhang ◽  
Alexey Kaplan ◽  
Stephen S. Howe ◽  
Gerard M. Wellington
Keyword(s):  
Climate Variability ◽  
Oxygen Isotope ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Decadal Climate Variability ◽  
The South ◽  
Decadal Climate

Role of the South Pacific Convergence Zone in West Antarctic Decadal Climate Variability

2019 ◽  
Vol 46 (12) ◽  
pp. 6900-6909 ◽  
Author(s):  
Kyle R. Clem ◽  
Benjamin R. Lintner ◽  
Anthony J. Broccoli ◽  
James R. Miller
Keyword(s):  
Climate Variability ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Decadal Climate Variability ◽  
The South ◽  
West Antarctic ◽  
Decadal Climate

scholarly journals Revisiting remote drivers of the 2014 drought in South-Eastern Brazil

2020 ◽  
Vol 55 (11-12) ◽  
pp. 3197-3211
Author(s):  
Kathrin Finke ◽  
Bernat Jiménez-Esteve ◽  
Andréa S. Taschetto ◽  
Caroline C. Ummenhofer ◽  
Karl Bumke ◽  
...  
Keyword(s):  
Indian Ocean ◽  
General Circulation ◽  
Circulation Model ◽  
Tropical Pacific ◽  
South Atlantic ◽  
The South ◽  
South Eastern ◽  
Eastern Brazil ◽  
The Indian Ocean ◽  
Sst Anomalies

Abstract South-Eastern Brazil experienced a devastating drought associated with significant agricultural losses in austral summer 2014. The drought was linked to the development of a quasi-stationary anticyclone in the South Atlantic in early 2014 that affected local precipitation patterns over South-East Brazil. Previous studies have suggested that the unusual blocking was triggered by tropical Pacific sea surface temperature (SST) anomalies and, more recently, by convection over the Indian Ocean related to the Madden–Julian Oscillation. Further investigation of the proposed teleconnections appears crucial for anticipating future economic impacts. In this study, we use numerical experiments with an idealized atmospheric general circulation model forced with the observed 2013/2014 SST anomalies in different ocean basins to understand the dominant mechanism that initiated the 2014 South Atlantic anticyclonic anomaly. We show that a forcing with global 2013/2014 SST anomalies enhances the chance for the occurrence of positive geopotential height anomalies in the South Atlantic. However, further sensitivity experiments with SST forcings in separate ocean basins suggest that neither the Indian Ocean nor tropical Pacific SST anomalies alone have contributed significantly to the anomalous atmospheric circulation that led to the 2014 South-East Brazil drought. The model study rather points to an important role of remote forcing from the South Pacific, local South Atlantic SSTs, and internal atmospheric variability in driving the persistent blocking over the South Atlantic.

scholarly journals A New Paradigm for South Pacific Climate Variability and Predictability

2021 ◽  
Author(s):  
Jiale Lou ◽  
Terence O'Kane ◽  
Neil Holbrook
Keyword(s):  
Climate Variability ◽  
Southern Oscillation ◽  
South Pacific ◽  
Decadal Climate Variability ◽  
The South ◽  
New Paradigm ◽  
Coherent Noise ◽  
Decadal Climate ◽  
South Pacific Climate ◽  
Pacific Climate Variability

Abstract Pacific climate variability is largely understood based on El Niño–Southern Oscillation (ENSO), the North Pacific focused Pacific decadal oscillation (PDO) and/or the whole of Pacific region interdecadal Pacific oscillation – which respectively represent the dominant modes of interannual and decadal climate variability. However, the role of the South Pacific, including atmospheric drivers and cross-scale interactions between interannual and decadal climate variability, has received considerably less attention. Here we propose a new paradigm for South Pacific climate variability whereby the Pacific-South American (PSA) mode, characterised by two mid-tropospheric modes (PSA1 and PSA2), provides coherent noise forcing that acts to excite multiple spatiotemporal scales of oceanic responses in the upper South Pacific Ocean ranging from seasonal to decadal. While PSA1 has long been recognised as highly correlated with ENSO, we find that PSA2 is critically important in generating a sea surface temperature (SST) quadrupole pattern in the extratropical South Pacific. This sets up a precursor that optimally determines the predictability and evolution of SST 9 months in advance of the peak phases of both the leading South Pacific SST mode and ENSO. Our results show that the atmospheric PSA mode is the key driver of oceanic variability in the South Pacific subtropics.

An Enhanced Influence of Tropical Indian Ocean on the South Asia High after the Late 1970s

2012 ◽  
Vol 25 (20) ◽  
pp. 6930-6941 ◽  
Author(s):  
Xia Qu ◽  
Gang Huang
Keyword(s):  
Indian Ocean ◽  
South Asia ◽  
Tropical Indian Ocean ◽  
Tropospheric Temperature ◽  
Decadal Change ◽  
The South ◽  
South Asia High ◽  
The Impact ◽  
Change In Mean ◽  
Sst Anomalies

Abstract The tropical Indian Ocean (TIO)’s influence on the South Asia high (SAH)’s intensity experiences a decadal change in the late 1970s; after (before) the decadal shift, the influence is significant (insignificant). The present study investigates the role of tropospheric temperature in relaying the impact of sea surface temperature (SST) to the SAH and the change in the TIO’s influence. During the two epochs, the local tropospheric temperature responses to the TIO warming are distinct—more significant during the second epoch. It is inferred that this change may be responsible for the strengthening of the TIO’s influence on the SAH. Encouragingly, the ensemble simulations accurately capture the time of the decadal change, indicating that the enhanced influence is attributed to the SST forcing. There are two possible reasons for the change in the TIO–SAH relationship. The first reason is the change in the locations of the SST anomalies in the TIO. During the second epoch, positive SST anomalies lie in the Indian Ocean warm pool. Through the background vigorous convection and moist adjustment, the SST anomalies affect largely the tropospheric temperature and thus the SAH. The second reason is the decadal change in mean SST and the SST variability. During the recent decades, both the background SST and the variability of the TIO SST increase, which enhance the influence of the SST anomalies on the atmosphere. The influence of the remote oceanic forcing on the enhanced TIO–SAH relationship and its comparison with the contribution of the TIO SST are also discussed.

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