平流层极涡偏移对我国冬季降水的影响

Influences of the Deflection of Stratospheric Polar Vortex on Winter Precipitation of China

利用1970—2010年NCEP/NCAR再分析资料、我国160站月平均降水资料分析了平流层极涡向欧亚大陆偏移与我国冬季降水的关系。结果表明:1月极涡偏欧亚大陆强度指数与同期1月降水的显著正相关区域主要分布在我国中部大面积地区及新疆西南部的少数地区,显著负相关区域主要分布在新疆中部;相对1月而言,与后期2月显著正相关区域仍然主要分布在我国的中部地区但向西北方向延伸,使得华中北部、华北南部相对减少,而华北西部、西北东部等地区增大。对流层环流形势显示出在欧亚型强极涡年的1月,东亚冬季风和东亚大槽异常减弱,我国内陆中东部东南风距平显著,而贝加尔湖北部北风距平显著,南下的冷空气与暖湿气流交汇地区较常年偏北,同时我国中部地区低层水汽向上传播也明显增强,存在显著的水汽强辐合中心。

Using NCEP/NCAR reanalysis data and monthly precipitation data of 160 stations in China from 1970 to 2010 provided by National Climate Center, the deflection intensity variation of the stratospheric polar vortex, which moves toward the Eurasia, is analyzed and the relationship between the deflection intensity indexes in winter and the precipitation in the corresponding and later period is also studied by means of wavelet analysis, correlation analysis, composite analysis and so on. Results show that there is a dominant interannual oscillation period of about 6--8 years for the deflection intensity indexes. The interannual os- cillation period is roughly 8 years from the 1970s to the mid and late 1980s, but it shortens to 6 years from the late 1980s to the early 2000s. Positive phase oscillation occurred mainly in the late 1980s, 1990s and recent years. The deflection of the stratospheric polar vortex, which moves toward the Eurasia in January, has a very important impact on precipitation in the same period and later in February. The same period of signifi- cant positive correlation between the deflection intensity index in January and precipitation in January mainly occurs in central China and southwest Xinjiang, but significant negative correlation is also found in central Xinjiang. The later t^eriod of significant positive correlation between the deflection intensity index in January and precipitation in February is also mainly located in central China, but extends northwest- ward, making precipitation in north of central China and south of North China relatively reduced, while precipitation in west of North China and east of Northwest China relatively increased. From the analysis of circulation situation background, it can be summarized that strong Eurasian polar vortex in January may lead to reduced East Asian trough and East Asian winter monsoon. The departure of the southeast wind is remarkable in central and eastern China, which is easy for warm and humid air mov- ing toward the northwest of China. The northerly anomaly is remarkable in north Lake Baikal region, which makes cold air and warm air meet to the north of normal situation. Also, lower humid air transmit upward obviously increases, and significant strong convergence center appears in central China. It is found that there is a significant negative correlation between the index of the Eurasian polar vortex intensity and the index of East Asian winter monsoon in January, which passes the test of 0.05 level.