中文摘要：

利用滤波、EOF和合成分析等统计方法及NCEP和NOAA提供的资料，分析了与2008年初我国南方罕见持续性冰冻雨雪天气有关的水汽输送演变情况，发现持续性与热带大气季节内振荡（MJO）和中低纬地区高低层环流的30-60天低频振荡关系体现为：当MJO活动以印度洋中东部赤道地区对流加强、印度尼西亚对流受抑制为特征时，印度地区700hPa出现低频气旋有利于70～80°E的槽加深。与此同时，我国台湾以东洋面出现低频反气旋，有利于西太平洋副高加强。低压槽和副热带高压（副高）之间的偏南风导致孟加拉湾和南海的水汽同时向我国南方地区输送。与低层系统相配，200hPa低频反气旋位于南压大陆，在该低频反气旋东北侧则为低频气旋，二者之间的低频西北风与低层的低频南风构成了反Hadley型局地经向环流，并导致高层西风急流入口区反气旋侧的高层辐散区向南偏移，使低频经向环流的上升支控制我国南方地区，该上升气流将来自孟加拉湾和南海的水汽抬升至高层，十分有利2008年初我国罕见冻雨的降水异常。通过对比分析相同时段降水异常偏少的1993年中低纬高低层低频环流场，发现1993年的低频环流分布形势与2008年的相反，说明了季节内振荡确实是造成2008年初我国南方地区持续性降水的重要因素之一。

英文摘要：

Intraseasonal variations of water vapor transport associated with the southern-China snowstorms during January 2008 are analyzed statistically based on the NCEP/NCAR reanalysis data and TRMM data from NOAA. The analysis shows that when MJO （referring to Madden and Julian Oscillation accounting for about 50% of the variance） is in the phase characterized by the enhanced convection over the equatorial Indian Ocean and the suppressed convection over Indonesia, a 700-hPa low-frequency cyclone is located over India with an intensified southern trough while a low-frequency anticyclone is located to the east of Taiwan island with an intensified western Pacific subtropical high （WPSH）. An enhanced southerly flow between the southern trough and WPSH advects warm and moist air from both the Bay of Bengal and the South China Sea to southern China. Corresponding to these 700-hPa systems, a 200-hPa low-frequency anticyclone is located over South Asia while a low-frequency cyclone located to its northeast. An enhanced northwesterly flow between the anticyclone and cyclone works together with the 700-hPa southerly flow to form an anti-Hadley circulation on the equatorward side of southern China. The 200-hPa northwesterly flow also contributes to the southwestward shift of an East-Asian subtropical westerly jet with 200-hPa mass divergence over southern China, leading to the upward transport of water vapor and abnormal rain for the southern-China snowstorms. An opposite case has confirmed that the absence of the above mechanisms is responsible for the Southern-China below-normal rain in 1993 winter.