中文摘要：

利用NCEP/NCAR的逐日再分析资料和国家气象信息中心的常规观测站温度资料,首先分析了2011/2012年冬季中国低温异常过程中的两次典型寒潮过程和全国828个站平均温度低频振荡的变化特征,然后分析了温度场低频振荡随位相的演变,最后采用SVD（Singular Value Decomposition）方法研究了北半球中高纬度对流层中层低频环流系统配置对温度低频变化的影响。结果表明：1）2011/2012年冬季的寒潮和强降温过程是在全国区域平均温度存在较强的10~30 d低频振荡的背景下发生的,中国的北方和东南部地区温度的低频振荡较强是导致其降温显著的主要原因之一。2）SVD分析的第一模态显示,亚洲—西太平洋中低纬度与中高纬度的南北两支低频波列在东亚地区耦合,使我国中东部和东南部地区处于沿偏东路径南下的强冷空气中;第二模态显示,沿着喀拉海—乌拉尔山东侧—我国西部的低频波列引导源地冷空气沿西北路径南下相继影响我国西北和东北地区。这两个模态驱动了强度大、范围广的低频温度由升高向降低变化的振荡,是导致2011/2012年冬季寒潮发生和极端低温事件出现的环流系统。

英文摘要：

Using the daily data of NCEP/DOE Reanalysis II and the temperature data established by conventional ob- servation stations of the National Meteorological Information Center, cold waves during the extreme event of re- gional averaged temperature in China in the winter of 2011/2012 and the characteristics of the low-frequency os- cillation（LFO） of the mean temperature of 828 stations were analyzed.Then, the evolution of the low-frequency temperature field with phases was also analyzed, as well as the impact of the spatial configuration of the low-fre- quency circulation system in the mid-troposphere in the extratropical Northern Hemisphere on temperature changes by using the SVD method.The results showed that： （1） The increased cumulated frequency of the cold waves and the declining-temperature periods from No- vember 2011 to February 2012,accompanied by the wide temperature reduction,led to the extreme event of re- gional averaged temperature in China and an abnormally low temperature anomaly in North and Southeast China in the winter of 2011/2012. （2） Cold-temperature anomalies were the result of overlapping of the strong 10--30-day oscillation of tem- perature ,based on the seasonal temperature change trend.Low-frequency temperature in the western Tibetan Plat- eau and Yellow River basin and middle and lower reaches of the Yangtze River and the region to its south changed coherently,and two centers of strong oscillation were separately located in the Hetao area in the north and in southern China in the south.Whereas,the eastern Tibetan Plateau showed the opposite,with a decrease（ in- crease） of the low-frequency temperature in Northeast Inner Mongolia and Northeast China lagging behind the large area.As for northwest north,the LFO of temperature was mostly consistent with both of the two former. （ 3 ） The results of coupling spatial patterns and their temporal variations of the low-frequency height field at 500 hPa and the low-frequency temperature field of 2 days later by using the SVD