平流层极涡变化与我国冬季气温、降水的关系

Relationship between Stratospheric Polar Vortex Change and Temperature,Precipitation in Winter of China

利用国家气候中心提供的1951-2010年逐月环流指数资料,分析了北半球极涡强度指数、面积指数和中心强度指数的相关关系,并通过极涡强度指数的变化讨论了冬季北半球极涡强度的时间变化特征。结果表明,冬季极涡强度指数与面积指数和中心强度指数有较好的相关性,能够更好地反映冬季极涡强度的变化特征;冬季极涡存在准13年的年代际振荡周期,准5年的年际振荡周期在20世纪90年代后期较为明显。结合气温、降水观测资料和NCEP/NCAR月平均再分析资料,探讨了极涡强、弱不同年份我国冬季气温、降水和大气环流形势的变化。相对极涡弱值年而言,极涡强值年我国北方地区、东部地区特别是东北地区的气温偏高,西南大部分地区的气温偏低,长江流域和华南地区的气温变化不明显;我国南方地区降水偏多,长江中下游和华南地区的降水偏多最为明显,北方地区的降水略有减少;500hPa高度场上高纬度地区的位势高度降低,中高纬度的位势高度升高,冷空气向极地聚集,东亚大槽减弱,我国东北和东部地区的气温偏高;同时东亚冬季风减弱,湿空气向我国内陆输送,长江流域和我国南方地区的降水偏多。

Using the monthly circulation index data of National Climate Center from 1951 to 2010, the relationship among the intensity, area and central intensity indexes of the Northern Hemisphere polar vor- tex are analyzed. And the temporal variation features of the polar vortex intensity in winter were discussed through the intensity index. The results show that the polar vortex intensity index has a good correction with the area index and the central intensity index, which can represent the change of the stratospheric po- lar vortex well in winter. The polar vortex mainly has a decadal oscillation period of 13 years and an inter- annual oscillation period of 5 years after the 1990s. The changes of temperature, precipitation and the general circulation in winter are discussed by the observation data and monthly mean reanalysis data from NCEP/NCAR. In relative strong years of polar vortex, the temperatures in North China and East China, especially in Northeast China are higher than that of relative weak years of polar vortex. At the same time the temperature in most of Southwest China is lower, but it has little change in the Yangtze River region and South China. And the precipitation is above normal in Southern China region especially in mid- and lower-reaches of the Yangtze River and South China, but below normal in the North China. Besides, it can be found that the 500 hPa potential height is higher in the mid- and high-latitudes and lower in the high latitude, while the polar vortex is relative strong. The circulation implies that the East Asian winter mon- soon and East Asian trough is weaker correspondingly. Under this situation, the cold air gathered around the polar and warm air flows to inland region, which causes the higher temperature in East China and Northeast China, and more precipitation in the southern China and the Yangtze River regions.