Contrasting the Indian and western North Pacific summer monsoons in terms of their intensity of interannual variability and biennial relationship with ENSO

ABSTRACT

The intensity of interannual variability (IIV) of the monsoon and monsoon–ENSO biennial relationship (MEBR) were examined and compared for both the Indian summer monsoon (ISM) and western North Pacific summer monsoon (WNPSM) during 1958–2018. Covariability of the IIV and MEBR were identified for the two monsoons. When the MEBR was strong (weak), the IIV of the monsoon was observed to be large (small). This rule applied to both the ISM and WNPSM. Out-of-phase relationships were found between the ISM and the WNPSM. When the IIV and MEBR of the ISM were strong (weak), those of the WNPSM tended to be weak (strong). During the period with a stronger (weaker) ENSO–Atlantic coupling after (before) the mid-1980s, the IIV and MEBR of the WNPSM (ISM) were observed to be stronger. The increasing influences from the tropical Atlantic sea surface temperature (SST) may trigger the observed seesaw pattern of the ISM and WNPSM in terms of the IIV and MEBR multidecadal variability. The results imply that tropical Atlantic SST may need to be given more attention and consideration when predicting future monsoon variability of the ISM and WNPSM.

Graphical Abstract

摘要

印度夏季风和西北太平洋夏季风是亚洲季风系统的重要组成部分, 研究这两个季风的变异规律具有重要的科学和现实意义。我们在研究中发现热带大西洋海温的影响在最近年代的显著增强可以激发印度和西北太平洋夏季风之间的‘跷跷板’现象, 引起这两个季风在年际变化强度和季风–ENSO准两年关系方面的年代际反位相变化。在80年代中期之后(之前), ENSO和热带大西洋 (热带印度洋) 海表面温度具有更强的耦合, 从而支持西北太平洋夏季风 (印度夏季风) 可以表现出更强的年际变化强度和季风–ENSO准两年关系。在预测未来的亚洲夏季风变化时, 热带大西洋海温的影响可能需要给予更多的考虑。

KEYWORDS:

• Indian summer monsoon
• western North Pacific summer monsoon
• ENSO
• intensity of interannual variability
• monsoon–ENSO biennial relationship

关键词:

• 印度夏季风
• 西北太平洋夏季风
• 厄尔尼诺
• 年际变化强度
• 季风–ENSO准两年关系

Acknowledgments

We thank the anonymous reviewers for their comments and suggestions, which helped to greatly improve the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 41776031]; the National Key Research and Development Program of China [grant number 2018YFC1506903]; the Guangdong Natural Science Foundation [grant number 2015A030313796]; the program for scientific research start-up funds of Guangdong Ocean University, and the Foundation for Returned Scholars of the Ministry of Education of China.