An Analysis of the Large-Scale Climate Anomalies Associated with the Snowstorms Affecting China in January 2008

Abstract

Extraordinarily frequent and long-lasting snowstorms affected China in January 2008, causing abovenormal precipitation, below-normal temperature, and severe icing conditions over central-southern China. These snowstorms were closely linked to the change in the Middle East jet stream (MEJS), which intensified and shifted southeastward. The change in MEJS was accompanied by southeastward shifts of the ridge and the trough over Europe and western Asia. The intensified MEJS also strengthened the trough embedded in the southern branch of the subtropical westerlies over the southern Tibetan Plateau, enhancing the water vapor transport from western Asia and the Bay of Bengal to China. In the meantime, the subtropical western Pacific high (SWPH) was stronger and its ridgeline was farther north than normal. The anomalous high slowed down the eastward propagation of weather systems to the Pacific and favored convergence of water vapor over central-southern China. The MEJS is usually strong when the Arctic Oscillation (AO) is positive and the SWPH is farther north than normal in La Niñ a winters. Compared to the SWPH and the Niñ o-3.4 sea surface temperature (SST), the MEJS and the AO exert stronger influences on the temperature and the precipitation over central-southern China, despite the fact that these possible impacting factors are not completely independent from each other. Although the La Niñ a event might contribute to the climate anomalies through its relation with the SWPH in January 2008, an analysis of historical events indicates that La Niñ a conditions alone can hardly cause severe and persistent snow conditions over central-southern China. In addition, compared to the Niñ o-3.4 SST and the SWPH, the conditions of December MEJS and AO exhibit stronger precursory signals of the variability of January temperature over central-southern China.

Observational and supportive modelling analyses of winter precipitation change in China over the last half century

“…Additionally, the abnormal winter of 2008 was more likely a result of a combined effect from different interannual climate modes (i.e. La Niña and strong Arctic oscillation), as was discussed in Wen et al (2009), rather than as a result of the slowly changing atmospheric conditions.…”

The combined effects of the ENSO and the Arctic Oscillation on the winter climate anomalies in East Asia

“…Their combined effects may be different compared to an individual effect. For example, the AO anomaly with a La Niña event was shown to be responsible for the frozen rain and snow storm disaster in southern China during January 2008 [26]. Additionally, in the 2009/2010 winter, the extremely negative AO was suggested as the main cause for the extremely low temperature and snow storm in northern China, while the ENSO was thought to have played a secondary role [27].…”

Observed triggering of tropical convection by a cold surge: implications for MJO initiation

“…Although the extratropical factors are thought to be the main cause of this disaster (e.g. Wen et al, 2009;Zhou et al, 2009;Han et al, 2011), an MJO which originated from the western Indian Ocean around mid-January also played a crucial role in the maintenance of the icy weather (Hong and Li, 2009). In this study, we will show that the initiation of this MJO case was preceded by a cold surge from West Asia.…”