Enhanced influence of the North Atlantic Oscillation on winter snowfall in northern China since 2000

Because of the profound impacts of snowfall in northern China on the economy society and human lives, it is essential to understand the physical mechanisms behind the variability of snowfall in this region. Based on the observational and reanalysis data during 1961–2018, this study examines the relationship of winter snowfall over northern China with the North Atlantic Oscillation(NAO). The results show that their relationship experiences an interdecadal change around 2000. During 2000–2018, the NAO is significantly and negatively correlated to winter snowfall in northern China. When the NAO is in the negative phase, the East Asian subtropical jet and polar front jet tend to move northward and southward, respectively, concomitant with an anomalous cyclonic circulation from Lake Balkhash to Lake Baikal in the middle and lower troposphere. Such an atmospheric background favors the increase of snowfall over northern China by empowering the interactions of cold air with moist airflows in the target region. However, during 1981–1999, the association of the NAO with the above atmospheric circulations seems inconspicuous, thereby reducing its relation to winter snowfall in northern China. Further investigation suggests that the enhancement of the connection between the NAO and aforementioned atmospheric circulations may result from the westward displacement of the NAO southern center from the former period to the latter period.