The Combined Effects of ENSO and Solar Activity on Mid-Winter Precipitation Anomalies Over Southern China

Ruili Wang,Hedi Ma,Yuan Gao,Anwei Lai,Chujie Gao,Ziniu Xiao,Xing Li,Xiao Li

doi:10.3389/feart.2021.771234

Abstract

Both the El Niño-Southern Oscillation (ENSO) and the 11-years solar cycle had been identified as important factors that may influence the wintertime southern China precipitation (SCP). However, the interactions between these two factors remain less noticed. In this study, the combined effects of the ENSO and the solar activity on mid-winter (January) SCP are investigated using observational and reanalysis data. Results suggest that both the ENSO and the solar activity are positively correlated with the SCP, although exhibiting distinct spatial patterns. Under different combinations of the ENSO and solar phases, the SCP anomalies show superposition of these two factors to some extent. Generally, the ENSO-related SCP anomalies tend to be enhanced (disturbed) when the ENSO and the solar activity are in-phase (out-of-phase). But this solar modulation effect appears more clear and significant under cold ENSO (cENSO) phase rather than under warm ENSO (wENSO) phase. Further analysis suggests, during the wENSO phase, solar influences on the Northern Hemisphere circulation are generally weak with little significance. In contrast, during the cENSO phase, the solar effect resembles the positive phase of the Arctic Oscillation but with an evident zonal asymmetric component. Its manifestation over the Asia-Pacific domain features by negative geopotential height anomaly over the West Asia and positive geopotential height anomaly over the East Asian coast, a pattern that is favorable for the SCP, thus causing a significant solar modulation on the cENSO-related precipitation anomalies. Further, the potential physical causes of solar effects on circulation are also discussed. Our results highlight the importance of considering solar cycle phase when ENSO is used to predict the East Asian winter climate.

Highlights

Dominated by the East Asian winter monsoon (EAWM), the winter climate over most part of China is characterized by low temperature and few precipitation owing to the influences of frequent cold surges
Respective El Niño-Southern Oscillation (ENSO) and Solar Signals in Precipitation Anomalies To compare the features of direct ENSO and solar influences on southern China (SC) precipitation (SCP), we analyze the ENSO and solar signals in mid-winter (January) precipitation obtained by the multiple linear regression (MLR) method, as are shown in Figures 2A,B, respectively
While the solar signal exhibits a region of enhanced precipitation centered over the Yangtze River Valley (YRV) and extending across most of the eastern China

Summary

Introduction

Dominated by the East Asian winter monsoon (EAWM), the winter climate over most part of China is characterized by low temperature and few precipitation owing to the influences of frequent cold surges. As had been demonstrated by a number of previous studies, the year-to-year variability of the SC precipitation (SCP) in winter can be largely attributed to the tropical sea surface temperature (SST) anomalies, as well as the modes of circulation variability over the mid-to-high latitudes (Liu Y. et al, 2014; Huang et al, 2017). Among these factors, the El Niño-Southern Oscillation (ENSO), which is the most dominant atmosphere–ocean coupled mode on interannual time scale, had been recognized as a very important factor that influences the SCP. Many studies had found that the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation, the different spatial patterns of ENSO and even the mid-latitude circulation anomalies, have the potential to modulate the ENSO impacts on SCP (Wang et al, 2008; Geng et al, 2017; Wu and Mao, 2017; Jia et al, 2019; Jiang et al, 2019; He et al, 2020)

Methods

Results

Discussion

Conclusion