长江中下游冬季降水特征和影响因素分析

Analyses of Winter Rainfall Variability and Influencing Factors in the Middle-Lower Reaches of Yangtze River

利用NCEP/NCAR再分析资料和NOAA提供的北极涛动(AO)指数、ENSO指数和海温资料,研究了1951/1952-2010/2011年长江中下游冬季降水年际和年代际变化的主要特征及其重要影响因素。结果表明,长江中下游冬季降水存在显著的年际和年代际变化。大气环流和海温异常对冬季降水异常都有重要影响。在大气环流方面,东亚冬季风增强(减弱)时,冬季降水偏少(偏多);欧亚遥相关型和西太平洋遥相关型与冬季降水成显著反相关关系;AO指数与冬季降水的关系则主要体现在年代际变化时间尺度上。在海温方面,冬季ENSO为暖(冷)位相,降水异常偏多(少)几率大;中东太平洋海温、印度洋海温和中国近海海温与冬季降水均有一定的联系。进一步的分析表明,东亚冬季风指数、欧亚遥相关型、西太平洋遥相关型、AO指数、中东太平洋海温、印度洋海温和中国近海海温这7个影响因素能解释长江中下游冬季降水变化方差的43.6%。

Using NCEP/NCAR reanalysis data and NOAA relevant data, the winter rainfall variation characteristics of the the middle-lower reaches of Yangtze River in 1951/1952-2010/2011 and the major influencing factors were analyzed. The results show that there is interannual and inter-decadal change of winter rainfall over the middle-lower reaches of Yangtze River. General circulation and SST have important influences on the winter rainfall： when East Asian winter monsoon is stronger （weaker）, winter rainfall less （more） in the circulation aspects. EU and WP have a significant inverse relationship with reference to the winter rainfall, whereas the in-phase linkage between AO and winter rainfall is primarily in the decadal scale. About SST, when winter ENSO is in warm （cold） phase, there tends to be positive （negative） precipitation anomalies. Middle East Pacific SST, Indian Ocean and China′s offshore SST perform important roles in winter rainfall causes. Regression analysis reveals that the seven factors could explain 43.6% of the variability of winter rainfall over the middle-lower reaches of Yangtze River.