A robust equatorial Pacific westerly response to tropical volcanism in multiple models
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A robust equatorial Pacific westerly response to tropical volcanism in multiple models Jing Chai1 · Fei Liu1,2,3 · Chen Xing1 · Bin Wang4 · Chaochao Gao5 · Jian Liu6 · Deliang Chen7 Received: 1 January 2020 / Accepted: 31 August 2020 © The Author(s) 2020
Abstract After each of the 1963 Agung, 1982 El Chichón, and 1991 Pinatubo eruptions, an El Niño was observed. The increased likelihood of an El Niño after a tropical eruption has also been found in long-term reconstructed proxy data. Through examining simulations over the last millennium by 11 different models, we show that a tropical volcano eruption can robustly excite a western-to-central equatorial Pacific (WCEP) westerly anomaly at 850 hPa in eight out of the 11 models; such a westerly anomaly is favorable for El Niño development. Under the volcanic forcing, there are significant extratropical continent surface cooling and tropical drying with negative precipitation anomalies over the South–South East Asia (SSEA), West African monsoon, and Intertropical Convergence Zone (ITCZ) regions. This common precipitation suppression response occurs in most of the models. Sensitivity experiments show that a WCEP westerly anomaly can be excited by the tropical land cooling, especially the SSEA cooling induced precipitation suppression rather than by the extratropical land surface cooling. Theoretical results show that a WCEP westerly anomaly is excited due to a Gill response to reduced precipitation over the SSEA and West African monsoon regions; and the SSEA contributes more than the West African monsoon does. The ITCZ weakening, however, excites an easterly wind anomaly. The models with more sensitive convective feedback tend to simulate an El Niño more easily, while a failed simulation of an El Niño after a robust westerly anomaly in some models calls for further studies on these models’ delayed responses to radiative forcing induced by volcano eruptions. Keywords El Niño · Large tropical volcanic eruption · Westerly anomaly · South–South East Asia · West African Monsoon · Precipitation suppression
1 Introduction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00382-020-05453-6) contains supplementary material, which is available to authorized users. * Fei Liu [email protected] 1
Earth System Modeling and Climate Dynamics Research Center, Nanjing University of Information Science and Technology, Nanjing, China
School of Atmospheric Sciences and Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-Sen University, Zhuhai 519082, China
2
3
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
4
Department of Atmospheric Sciences and Atmosphere‑Ocean Research Center, University of Hawaii at Manoa, Honolulu, HI 96822, USA
Volcano eruptions are a dominant external forcing for triggering interannual climate responses through injecting large amounts of sulfur dioxide into the stratosphere and 5
Department of Environme
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