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Atlantic Multidecadal Oscillation Modulates ENSO Atmospheric Anomaly Amplitude in the Tropical Pacific

Atlantic Multidecadal Oscillation Modulates ENSO Atmospheric Anomaly Amplitude in the Tropical... AbstractPrevious studies have demonstrated that the Atlantic multidecadal oscillation (AMO) could affect El Niño–Southern Oscillation (ENSO) through thermocline adjustment, with a stronger ENSO sea surface temperature (SST) amplitude during a negative AMO phase than during a positive phase. In this study, we find that the ENSO atmospheric anomaly amplitudes in the tropical Pacific during different AMO phases are not necessarily consistent with these ENSO SST changes. For El Niño episodes, the low-level wind and precipitation anomalies over the tropical Pacific in the boreal winter are more pronounced during the negative AMO phase than during the positive phase, corresponding well to the stronger SST anomalies. However, La Niña events during the negative AMO phase are accompanied by weaker atmospheric anomalies in the tropical Pacific, although their SST anomalies are stronger than those during the positive phase. We suggest that this mismatch between La Niña SST and atmospheric anomalies can be largely attributed to AMO decadal modulation. A positive AMO favors intensified trade winds and weakened precipitation in the central tropical Pacific by modifying Walker circulation. Therefore, when La Niña coincides with a positive AMO, the low-level easterly and negative precipitation anomalies are superimposed, which gives rise to stronger atmospheric perturbations. In contrast, under a negative AMO background, the atmospheric anomalies induced by La Niña anomalous SST are partly counteracted by the AMO remote decadal modulation, thereby resulting in weaker anomaly amplitudes. Here, we highlight that AMO decadal forcing needs to be considered when investigating ENSO atmospheric variabilities and related regional climate impacts. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

Atlantic Multidecadal Oscillation Modulates ENSO Atmospheric Anomaly Amplitude in the Tropical Pacific

Journal of Climate , Volume 35 (12): 13 – Jun 15, 2022

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0442
eISSN
1520-0442
DOI
10.1175/jcli-d-21-0603.1
Publisher site
See Article on Publisher Site

Abstract

AbstractPrevious studies have demonstrated that the Atlantic multidecadal oscillation (AMO) could affect El Niño–Southern Oscillation (ENSO) through thermocline adjustment, with a stronger ENSO sea surface temperature (SST) amplitude during a negative AMO phase than during a positive phase. In this study, we find that the ENSO atmospheric anomaly amplitudes in the tropical Pacific during different AMO phases are not necessarily consistent with these ENSO SST changes. For El Niño episodes, the low-level wind and precipitation anomalies over the tropical Pacific in the boreal winter are more pronounced during the negative AMO phase than during the positive phase, corresponding well to the stronger SST anomalies. However, La Niña events during the negative AMO phase are accompanied by weaker atmospheric anomalies in the tropical Pacific, although their SST anomalies are stronger than those during the positive phase. We suggest that this mismatch between La Niña SST and atmospheric anomalies can be largely attributed to AMO decadal modulation. A positive AMO favors intensified trade winds and weakened precipitation in the central tropical Pacific by modifying Walker circulation. Therefore, when La Niña coincides with a positive AMO, the low-level easterly and negative precipitation anomalies are superimposed, which gives rise to stronger atmospheric perturbations. In contrast, under a negative AMO background, the atmospheric anomalies induced by La Niña anomalous SST are partly counteracted by the AMO remote decadal modulation, thereby resulting in weaker anomaly amplitudes. Here, we highlight that AMO decadal forcing needs to be considered when investigating ENSO atmospheric variabilities and related regional climate impacts.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Jun 15, 2022

References