Characteristics of Blocking Events over Siberia for the Present and Future Climate Conditions, and the Implications for the Regional Climate in South China

An unexpected severe and prolonged snowstorm attacked South China in January 2008, caused a direct economic loss exceeding 53 billion RMB. The extensive damage brought by this extreme event is unambiguous comparing to that caused by tropical cyclones. For example, Typhoon Dujuan hitting the coast of Guangdong in 2003 caused only some 2.3billions RMB. At the same time, the snowstorm is unexpected actually highlighting the need to improve our understanding and thereof predict.While warmer winters along with global warming have drawn much attention from the public perceptually, this unusual and sudden chilling weather apparently highlights the potential threats brought by events of extreme weather and marks the importance to understand the reasons leading to their occurrences. For better disasters preparedness, it is therefore crucial to evaluate whether the occurrence of extreme cold weather events such as snowstorms and freezing rain would increase under global warming scenario.Prolonged cold spells or extreme snowstorms in South China are mainly attributed to the occurrence of blocking events in the vicinity of Siberia. Thus, a better understanding of the characteristics of the blocking would be a key to the wintertime regional climate variability in South China. In the meantime, understanding of the development mechanisms and predictability of Siberian blocking, as well as its influences to the winter conditions in South China remain limited. How the blocking characteristics vary in future is undoubtedly need to be addressed by scientists as well as policy makers, for preparedness and risk assessment.In this study, we will first characterize the blocking activities over Siberia in terms of intensity, duration and spatial structure. Then the influence of blocking activities to the winter climate in South China in a changing climate will be evaluated. By examining the Asian monsoon circulation anomalies as well as their connection with other climatic signals such as El Nino and Southern Oscillation and Arctic oscillation etc, the causes of extreme blocking events and consequently the extreme weather in South China, will be uncovered. This integrated study of Siberian blocking for present and future condition will enable us to not only advance the state-of-the-art of East Asian winter monsoon research, but also produce many results and findings of great importance for sustainable social-economical development of South China including Hong Kong.