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

Climate Dynamics
By: , and 

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Abstract

A wide range of sea surface temperature (SST) expressions have been observed during the El Niño–Southern Oscillation events of 1950–2010, which have occurred simultaneously with different global atmospheric circulations. This study examines the atmospheric circulation and precipitation during December–March 1950–2010 over the African Continent south of 15S, a region hereafter known as Southern Africa, associated with eight tropical Pacific SST expressions characteristic of El Niño and La Niña events. The self-organizing map method along with a statistical distinguishability test was used to isolate the SST expressions of El Niño and La Niña. The seasonal precipitation forcing over Southern Africa associated with the eight SST expressions was investigated in terms of the horizontal winds, moisture budget and vertical motion. El Niño events, with warm SST across the east and central Pacific Ocean and warmer than average SST over the Indian Ocean, are associated with precipitation reductions over Southern Africa. The regional precipitation reductions are forced primarily by large-scale mid-tropospheric subsidence associated with anticyclonic circulation in the upper troposphere. El Niño events with cooler than average SST over the Indian Ocean are associated with precipitation increases over Southern Africa associated with lower tropospheric cyclonic circulation and mid-tropospheric ascent. La Niña events, with cool SST anomalies over the central Pacific and warm SST over the west Pacific and Indian Ocean, are associated with precipitation increases over Southern Africa. The regional precipitation increases are forced primarily by lower tropospheric cyclonic circulation, resulting in mid-tropospheric ascent and an increased flux of moisture into the region.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title El Niño–Southern Oscillation diversity and Southern Africa teleconnections during Austral Summer
Series title Climate Dynamics
DOI 10.1007/s00382-014-2414-z
Volume 45
Issue 5
Year Published 2014
Language English
Publisher Springer
Publisher location Heidelberg
Contributing office(s) Earth Resources Observation and Science (EROS) Center
Description 17 p.
First page 1583
Last page 1599
Online Only (Y/N) N
Additional Online Files (Y/N) N