Characteristics of large-scale atmospheric circulations associated with the heavy winter snowfall of 2005/06

Abstract

With regard to large-scale atmospheric circulations, we examine the characteristics of the heavy winter snowfall of 2005/06 and discuss its cause.The East Asian winter monsoon intensity index indicates that the monsoon activity in December 2005 was the most pronounced in the past 50 years; this was mainly responsible for the occurrence of the persistent heavy snowfall.Extraordinary atmospheric circulation anomalies associated with the strong monsoon were observed, particularly in low-latitude regions.Large-scale cumulus convection was enhanced in the vicinity of the South China Sea and Philippine Sea, eventually generating an extremely strong anomalous anticyclone in the upper troposphere over southern China. It is suggested that the distinctive anticyclonic vorticity, which can generate stationary Rossby waves, contributes significantly to the reinforcement of the monsoon activity through eastward energy propagation. Compared with previous heavy snowfall winters, the remote forcing from the tropics is more evident in the heavy winter snowfall of 2005/06.