Changes in the relationship between ENSO and the East Asian winter monsoon under global warming

Zixuan Jia,Massimo A Bollasina,Oliver Wild,Ruth Doherty,Chaofan Li

doi:10.1088/1748-9326/abca63

Abstract

Changes in the relationship between El Niño-Southern Oscillation (ENSO) and the East Asian winter monsoon (EAWM) at various global warming levels during the 21st century are examined using the Max Planck Institute Grand Ensemble Representative Concentration Pathway 8.5 experiments. The externally forced component of this relationship (i.e. forced by greenhouse gases and anthropogenic aerosols emissions) strengthens from present-day to +1.5 °C, and then weakens until +3 °C. These changes are characterized by variations in strength and location of the core of El Niño-related warming and associated deep convection anomalies over the equatorial Pacific leading to circulation anomalies across the Asian-Pacific region. Under global warming, the ENSO–EAWM relationship is strongly related to the background mean state of both the EAWM and ENSO, through changes in the EAWM strength and the shift of the ENSO pattern. Anthropogenic aerosols play a key role in influencing the ENSO–EAWM relationship under moderate warming (up to 1.5 °C).

Highlights

The East Asian winter monsoon (EAWM), a prominent feature of the northern hemisphere atmospheric circulation during boreal winter, has a large influence on the weather and climate of the Asian-Pacific region (e.g., Chang, 2006)
Future projections of the ENSOEAWM relationship for the 21st century have been investigated (e.g., Wang et al, 2013; Jiang et al, 2013; Xu et al, 2015); this topic has received much less attention compared to the analysis of the link between ENSO and the East Asian monsoon during the summer
The spatial patterns of simulated SST and Outgoing Long-wave Radiation (OLR) anomalies are broadly similar to those found in observations (Figs. 1a, b, d, e); the model captures well the location of the two prominent low-tropospheric circulation features, the anticyclone over the western tropical Pacific and the cyclone over the north-eastern extratropical Pacific (Figs. 1c, f)

Summary

Introduction

The East Asian winter monsoon (EAWM), a prominent feature of the northern hemisphere atmospheric circulation during boreal winter, has a large influence on the weather and climate of the Asian-Pacific region (e.g., Chang, 2006). The observed ENSO-EAWM relationship displays substantial multi-decadal variability during the 20th century/ early 21st century (e.g., Li and Ma, 2012; He and Wang, 2013; Jo et al, 2015; Li et al, 2015), with corresponding pronounced variations in the teleconnections patterns over East Asia and the Pacific. There is no consensus on the factors affecting these fluctuations, which have been ascribed to the influence of large-scale internal climate variability (i.e., the Pacific decadal oscillation (e.g., Kim et al, 2017) and the Atlantic Multidecadal Oscillation (e.g., Geng et al, 2017)), interdecadal variations of ENSO (e.g., Wang et al, 2009) and the EAWM (e.g., Ding et al, 2014), and external forcing, either natural (e.g., solar cycle; Zhou et al, 2013) or anthropogenic (e.g., the shift of the climatological Walker circulation due to green house warming; He and Wang, 2013). Future projections of the ENSOEAWM relationship for the 21st century have been investigated (e.g., Wang et al, 2013; Jiang et al, 2013; Xu et al, 2015); this topic has received much less attention compared to the analysis of the link between ENSO and the East Asian monsoon during the summer

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Conclusion