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- Title
Unusual Anomaly Pattern of the 2015/2016 Extreme El Niño Induced by the 2014 Warm Condition.
- Authors
Zhong, Wenxiu; Cai, Wenju; Zheng, Xiao‐Tong; Yang, Song
- Abstract
The warm center of the 2015/2016 extreme El Niño was located further to the west compared to previous extreme events, causing vastly different social‐economic impacts. Though many studies investigated ocean‐atmosphere couplings responsible for its large magnitude, the dynamics that govern the unique structure of the event remain elusive. Here we show that a local ocean‐atmosphere feedback among convection‐induced surface winds, oceanic upwelling and sea surface temperature in the far‐eastern Pacific, resulted in a boreal summer cooling tendency along the South American coast. It canceled warming in the far‐eastern equatorial Pacific that would otherwise develop, leading to the distinctive anomaly pattern of the 2015/2016 El Niño. These processes were initially triggered by the leftover anomalous warm sea surface temperature and positive moist static energy over the northeastern tropical Pacific in the following boreal spring of the 2014 warm event. Plain Language Summary: Extreme El Niño events exert severe impacts on society, but predicting extreme events is challenging. These events are rare and distinctive from one to another in their spatial pattern, generating different regional impacts and disasters. In particular, the 2015/2016 extreme El Niño features a more westward warm center of sea surface temperature anomalies, compared to that of 1982/1983 or 1997/1998. Our analysis of observations relates this unique anomaly pattern to the preceding warm tropical Pacific in 2014. That is, rainfall anomalies over the eastern Pacific were initially fueled by the leftover unstable energy over the northeastern tropical Pacific. Then the center of anomalous rainfall was restricted to the north of the equator through a local ocean‐atmosphere feedback among convection‐induced surface flows, oceanic upwelling and sea surface temperature. The positive feedback resulted in a summer cooling tendency along the South American coast, which offset warm SST anomalies and caused the unusual pattern of the 2015/2016 extreme El Niño. Our further investigation suggested that the state of the eastern Pacific before the developing summer is also essential for the development of other El Niño events. Key Points: The South American coastal cooling process led to a westward propagation of the 2015/2016 El Niño warm center after the boreal springConvective activity relating to the 2014 warm condition induced cooling tendency along the South American coast through a feedback loopThis antecedent state of the eastern Pacific played a crucial role in the unique spatial pattern of the 2015/2016 El Niño
- Subjects
OCEAN temperature; UPWELLING (Oceanography); RAINFALL anomalies
- Publication
Geophysical Research Letters, 2019, Vol 46, Issue 24, p14772
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2019GL085681