The impact of the Southern Annular Mode on future changes in Southern Hemisphere rainfall

A robust positive trend in the Southern Annular Mode (SAM) is projected for the end of the 21st century under the Representative Concentration Pathway 8.5 scenario, which results in rainfall decreases in the midlatitudes and increases in the high latitudes in the Southern Hemisphere (SH). We find th...

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Bibliographic Details
Published in:Geophysical research letters 2016-07, Vol.43 (13), p.7160-7167
Main Authors: Lim, Eun‐Pa, Hendon, Harry H., Arblaster, Julie M., Delage, Francois, Nguyen, Hanh, Min, Seung‐Ki, Wheeler, Matthew C.
Format: Article
Language:English
Subjects:
Annular
Antarctic Oscillation
Climate
Climate models
CMIP5
Components
Drying
El Nino
El Nino-Southern Oscillation event
Latitude
Meteorology
Ocean circulation
Ocean currents
Ocean temperature
Rain
Rainfall
RCP8.5
Robustness
Seasons
Souther Hemisphere rainfall
Southern Annular Mode
Southern Hemisphere
Southern Oscillation
Summer
Trends
Warm seasons
Winter
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Summary:A robust positive trend in the Southern Annular Mode (SAM) is projected for the end of the 21st century under the Representative Concentration Pathway 8.5 scenario, which results in rainfall decreases in the midlatitudes and increases in the high latitudes in the Southern Hemisphere (SH). We find that this SAM trend also increases rainfall over the SH subtropics in austral summer but not in winter, leading to a pronounced wintertime poleward expansion of the subtropical dry zone. These dynamically driven rainfall changes by the SAM appear to oppose the thermodynamically driven projected rainfall changes in the SH subtropics and midlatitudes, whereas the two components reinforce each other in the high latitudes. However, we show that most climate models fall short in capturing the observed SAM component driven by the El Niño–Southern Oscillation and associated rainfall in the austral warm seasons, which limits our confidence in quantifying the contribution of the SAM to projected rainfall changes. Key Points SAM‐driven rainfall will mitigate the drying of the SH subtropics in summer under RCP8.5 A poleward expansion of the SH subtropics due to the positive trend in the SAM is a winter phenomenon CMIP5 models poorly simulate the observed relationship between the SAM and El Nino‐Southern Oscillation
ISSN:0094-8276
1944-8007
DOI:10.1002/2016GL069453