Synergistic effect of El Niño and the North Pacific Oscillation on wintertime precipitation over Southeastern China and the East China Sea Kuroshio area

Abstract

Wintertime precipitation in China is most pronounced over the southeastern area, and the Kuroshio in the East China Sea anchors a prominent precipitation band over the warm side of the sea surface temperature front. Previous studies have suggested that many factors contribute to the interannual variation of the precipitation over southeastern China (SC), whereas less attention has been paid to precipitation variability over the East China Sea Kuroshio (ECSK) area. This study focuses on the interannual variation of wintertime precipitation over the SC and ECSK areas. Empirical orthogonal function analysis reveals a spatially uniform pattern from SC to the ECSK area. Composite analysis shows that an El Niño event intensifies wintertime precipitation over our target region, and this effect is tripled when an El Niño follows a positive North Pacific Oscillation (NPO) event in the previous winter. The positive NPO event in the previous winter intensifies the El Niño event via the Victoria mode ocean bridge and the subsequent Bjerknes feedback. In comparison with single-factor El Niño events, a much weaker Walker cell induced by the joint event induces a much weaker regional Hadley cell through anomalous descending motion over the western tropical Pacific. The weakened regional Hadley circulation over the western Pacific directly enhances the precipitation over the SC and ECSK area. In this study, the synergistic effect of an El Niño event and a positive NPO event indicates that the influence of the El Niño event can be amplified by the positive NPO event in the previous winter.

Synergistic effect of boreal autumn SST over the tropical and South Pacific and winter NAO on winter precipitation in the southern Europe

“…The synergistic effects of forcing and physical processes used in this study is the same as previous studies [36][37][38][39][40][41] when the normalized index is above (below) 0.7 (−0.7) considering both the significance and the number of positive (negative) events.…”

“…Particularly, this concept of synergistic effect has been widely used to understand the variability of climate 37,38 and extreme climate [39][40][41] . Therefore, we adopt the concept of synergistic effect in Li et al (2019) 36 to investigate whether the joint events of negative NAO and preceding season SSTA produces significantly stronger and more frequent occurrence of winter precipitation than they occur in isolation to better understand the influencing mechanism of SEWP variability.…”

Atlantic Multidecadal Oscillation modulates the relationship between North Pacific Oscillation and winter precipitation in North China Plain

“…The NPO's southern lobe is near the Hawaiian Islands, and the northern lobe is close to the Aleutian Islands (Wang et al, 2011). The winter NPO not only influence the climate of North America in its downstream (Baxter & Nigam, 2015; Furtado et al, 2012; Lee et al, 2015; Rogers, 1981; Sung et al, 2019) but also the climate of East Asia in its upstream (Chen & Song, 2018; Ding et al, 2015, 2018; Han et al, 2023; Hu et al, 2023; Li & He, 2016; Li et al, 2019; Pu et al, 2019; Sun & Li, 2022; Sung et al, 2021; Tian et al, 2024; Wang & Feng, 2011; Zhou & Xia, 2012).…”

Increasing Precipitation in Early Winter Over the Southern China During the Past 40 years

“…Winter precipitation over southern China (SC), usually accompanied by strong cooling, has a significant impact on local agriculture and other economic activities. Therefore, although the SC precipitation is much lower in winter than in summer, variations in winter precipitation have also received extensive attention (Ding & Li, 2017; Huang et al., 2019; Jia & Ge, 2017; Lou et al., 2017; Ma et al., 2019; Sun & Li, 2022; Wang et al., 2019, 2022; Zhang et al., 2021; Zong et al., 2014).…”