Breakdown of the relationship between Australian summer rainfall and ENSO caused by tropical Indian Ocean SST warming

Breakdown of the relationship between Australian summer rainfall and ENSO caused by tropical... AbstractThe relationship between El Niño–Southern Oscillation (ENSO) and Australian summer rainfall (ASR) during 1960–2015 experienced an interdecadal change around the mid-1980s. Before the mid-1980s, ASR was significantly correlated with tropical central Pacific (TCP) sea surface temperature (SST), whereas after then it was not.While the El Niño was always independent from ASR, the La Niña had a close relationship with ASR. However, this relationship was weakened after the mid-1980s.The Indian Ocean SST warming might contribute to the weakening relationship between La Niña and ASR. For La Niñas before the mid-1980s, the negative SSTA over TCP and southern tropical Indian Ocean induced a large-scale lower-level cyclonic anomaly over Australia, leading to nearly uniform positive precipitation over Australia. In this manner, a significant relationship between ASR and La Niña was established. On the contrary, for the La Niñas after the mid-1980s, because of the Indian Ocean SST warming, the equatorial eastern Indian Ocean and Maritime Continent presented positive SSTAs and enhanced moisture, favoring enhanced rainfall anomalies over the equatorial Maritime Continent. This enhanced rainfall condensation heating induced a lower-level cyclonic anomaly to the west of Australia. The northerly anomalies at the eastern flank of this cyclonic anomaly counteracted the southerly anomalies at the western flank of the cyclonic anomaly over eastern Australia induced by the negative TCP SSTA, leading to insignificant circulation and rainfall anomalies over Australia. As such, being interfered with by the equatorial Maritime Continent heating, the relationship between ASR and La Niñas was weakened. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

Breakdown of the relationship between Australian summer rainfall and ENSO caused by tropical Indian Ocean SST warming

Journal of Climate , Volume preprint (2017): 1 – Dec 20, 2017

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0442
D.O.I.
10.1175/JCLI-D-17-0132.1
Publisher site
See Article on Publisher Site

Abstract

AbstractThe relationship between El Niño–Southern Oscillation (ENSO) and Australian summer rainfall (ASR) during 1960–2015 experienced an interdecadal change around the mid-1980s. Before the mid-1980s, ASR was significantly correlated with tropical central Pacific (TCP) sea surface temperature (SST), whereas after then it was not.While the El Niño was always independent from ASR, the La Niña had a close relationship with ASR. However, this relationship was weakened after the mid-1980s.The Indian Ocean SST warming might contribute to the weakening relationship between La Niña and ASR. For La Niñas before the mid-1980s, the negative SSTA over TCP and southern tropical Indian Ocean induced a large-scale lower-level cyclonic anomaly over Australia, leading to nearly uniform positive precipitation over Australia. In this manner, a significant relationship between ASR and La Niña was established. On the contrary, for the La Niñas after the mid-1980s, because of the Indian Ocean SST warming, the equatorial eastern Indian Ocean and Maritime Continent presented positive SSTAs and enhanced moisture, favoring enhanced rainfall anomalies over the equatorial Maritime Continent. This enhanced rainfall condensation heating induced a lower-level cyclonic anomaly to the west of Australia. The northerly anomalies at the eastern flank of this cyclonic anomaly counteracted the southerly anomalies at the western flank of the cyclonic anomaly over eastern Australia induced by the negative TCP SSTA, leading to insignificant circulation and rainfall anomalies over Australia. As such, being interfered with by the equatorial Maritime Continent heating, the relationship between ASR and La Niñas was weakened.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Dec 20, 2017

References

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