Impact of the March Arctic Oscillation on the South China Sea summer monsoon onset

Abstract

This study reveals that the South China Sea summer monsoon (SCSSM) onset is closely linked to the preceding March Arctic oscillation (AO), the dominant mode of atmospheric circulation over extratropical Northern Hemisphere. The physical processes for the impact of the March AO on the SCSSM onset are further examined. March AO leads to an anomalous low-level cyclone over subtropical western North Pacific (WNP) via eddy-mean flow interaction. The southwesterly wind anomalies to the southeastern side of the anomalous cyclone weaken the climatological trade winds, which contribute to warm sea surface temperature (SST) anomalies over tropical western-central North Pacific via reduction of surface evaporation and latent heat flux. These warm SST anomalies excite an atmospheric Rossby wave response and reinforce the anomalous cyclone over the subtropical WNP. Via the above positive atmosphere-ocean interaction, the anomalous cyclone induced by the March AO could persist through the whole spring and shift equatorward. This anomalous cyclone creates favourable environment for the SCSSM onset via weakening the WNP subtropical high and is conducive to the transition of the lowlevel zonal wind. Further analysis indicates that the March AO-SCSSM onset relationship is independent of El Niño-Southern Oscillation (ENSO). This result suggests that, besides the dominant tropical system (i.e., ENSO), interannual variation of the SCSSM onset also has a close relation with the dominant extratropical atmospheric system (i.e., AO), which may provide additional source for the seasonal prediction of the monsoon onset.

Impact of March North Atlantic Oscillation on Indian Ocean Dipole: role of air–sea interaction over the Western North Pacific

“…2a,b,3c,d). These findings correspond with those from Hu et al (2021), and they demonstrated that the equatorward displacement of the WNP cyclone induced by the positive March AO favors the early onset of the South China Sea summer monsoon. Previous studies have indicated the role of the WNP atmospheric circulation anomalies on the development of IOD (Kajikawa et al 2003;Huang and Shukla 2007).…”

“…2a-c, 3c-d, 4a-c; Gong et al 2011). Moreover, Rossby wave response associated with positive diabatic heating has the strongest westerly wind to the south of the heating center (Gill 1980;Hu et al 2021); accordingly, warm SSTAs and cyclonic circulations develop equatorward (Fig. 2a-c, 3c-d, 4a-c).…”

Relative humidity variation derived from tree‐ring δ18O and possible large‐scale atmospheric circulations linkage over the Guanzhong Plain, central northern China, since 1760 CE

“…One reason is that springtime AO has a direct impact on the East Asian Summer Monsoon precipitation over East Asia (Gong et al ., 2011; Chen et al ., 2015a). And, by modulating the tropical Pacific SST and ENSO, AO could also impact the monsoon activity over East Asia (Chen et al ., 2014; 2015b; Hu et al ., 2020).…”

Roles of synoptic‐scale waves and intraseasonal oscillations in the onset of the South China Sea summer monsoon

“…The onset of the SCSSM, which has been studied and debated for decades, is not a novel topic (Xie et al, 1998;Lu and Chan, 1999;Ding and Chan, 2005;Mao and Chan, 2005;Ronghui et al, 2006;Wen et al, 2006;Ding et al, 2008;Wang et al, 2009;Wu, 2010;Hu et al, 2020Hu et al, , 2021. However, studying the roles of SSWs in the SCSSM onset may provide additional insights.…”