东北夏季极端低温的变化特征及其与太平洋海温异常的关系

Spatial-temporal variations of summer extreme low temperature in northeast China and its relationship with SST anomaly over the Pacific

利用1958—2007年全球海温、位势高度月平均资料和中国东北地区64个测站的夏季地面气温等资料,分析了中国东北地区夏季极端低温的时空变化特征,及其与大气环流和海温异常之间的关系,研究结果如下:(1)近50a来中国东北夏季极端低温事件频数在年际变化的时间尺度上主要存在两种模态:全区一致变化型和南北反相变化型;(2)东北夏季极端低温频数与乌拉尔山高压,东亚大槽,阿留申低压,东北冷涡密切相关;(3)东北夏季极端低温与赤道东太平洋海温存在遥相关关系。在1990s初期以前,在E1 Nino发生年或翌年基本都对应东北夏季极端低温年,但1990s初期开始,El Nino发生年与东北地区夏季极端低温的对应关系遭到破坏;(4)东北夏季极端低温事件频数的年际变化与西太平洋暖池海温异常密切相关。进一步研究表明西太平洋暖池海温异常会影响东北地区上空的环流,致使东北夏季极端低温异常。

By using the data set of the mean monthly global sea surface temperature and geopotential height fields from 1958 to 2007 and the surface air temperature of 64 stations in northeast China during the same period, the spatial-temporal variations of summer extreme low temperature （SELT） in northeast China, and also its relationship with atmospheric circulation and the sea surface temperature anomalies are analyzed. The results suggest ： （ 1 ） over the past 50 a the frequency of summer extreme low tempera- ture had two modes： large-scale consistent mode and antiphase mode between north and south; （2）the frequency of summer extreme low temperature in north-east China is associated with the blocking highs in the Ural, the east Asian trough, the Aleutian low and northeast cold vortex; （3）the SST in the east e-quatorial Pacific is related to summer extreme low temperature in northeast China. Before the early 1990s, the occurrence of summer extreme low temperature was well consistent with the appearance of the EI Nino in the eastern equatorial Pacific, but their relations changed after early 1990s; （4）the western Pacific warm pool is the key area that affects the summer extreme low temperature over northeast China. Further research shows that the ~estern Pacific warm pool tends to affect the circulation over the northeast China.