中国东北夏季温度年代际变化特征

东北地区夏季温度变化主要有4个独立模态,其中EOF1呈全区一致型为第一模态,占总方差贡献的72%左右,其时间系数呈现多年代际尺度变化;其他3个模态仅分别占总方差贡献的10%、4%和3%,表现出受海洋、地形及纬度差异的影响,呈南北向、东西向和山脉与平原地区的反向异常分布型;突变和小波分析进一步揭示EOF1模态的多年代际尺度变化具有突变性质,2007~2010年受20 a左右周期影响,东北地区温度变化全区一致的模态时间系数处于负值为主的阶段,值得关注。东北地区夏季温度变EOF1模态与北半球500 hPa高度场和对流层中上层纬向风场(西风急流)在30oN~40oN呈环球尺度带状显著正相关分布,在东北亚地区纬度较高,可达60oN附近,而且该区500 hPa高度场与东北夏季温度EOF1模态多年代际变化近于同步。EOF1模态与靠近亚洲大陆沿岸和西太平洋暖池(包括印度洋的中部和北部)、南太平洋环澳大利亚、靠近北美大陆及北大西洋北部的漂流区和北赤道漂流区的海表温度存在显著的同步正相关,而与太平洋海表温度的年代际振荡模态亦有较显著的正相关;表明东北地区夏季温度的EOF1模态与北半球海-气系统多年代际变化联系密切,同时也受到全球变暖的影响。

Interdecadal Change Characteristics of Summer Temperature in Northeast China

Using monthly average temperature data at 26 stations in Northeast China in 1961-2010 and the NCEP/NCAR monthly reanalysis data,the interdecadal characteristics of summer temperature anomaly over Northeast China is investigated.It is found that there are 4 different patterns of summer temperature anomaly over Northeast China by applying empirical orthogonal functions(EOFs) analysis to monthly mean summer temperature anomalies.The EOF1 presents a pattern with changes in the same direction,holding about 72% of the total variance contribution,and its time factors show multiple interdecadal variation.Three other patterns hold 10%,4% and 3% of the total variance contribution respectively,showing north-south,east-west and mountain-plain anomaly patterns with changes in different direction,and the influence of ocean,terrain,and the difference of latitude.Multiple interdecadal variation of mode EOF1 has mutation properties further analyzed by mutation and wavelet analysis,and influenced by a period of 20 a,the time factors mainly were minus during 2007 to 2010,which should be paid more attention.Mode EOF1 is significant positive correlation with geopotential height in 500 hPa and U-wind in upper troposphere(Westerly Jet) of 30oN-40oN,presenting a global belt distribution.In northeast Asia,the positive correlation zone reaches 60oN,and geopotential height in 500 hPa changes in nearly the same direction with the multiple interdecadal variation of mode EOF1.Mode EOF1 is significant positive correlation with sea surface temperature(SST) in Asian coast of Pacific,the Western Pacific Warm Pool(including the north-central areas of Indian Ocean),the south Pacific surrounding Australia,the North America coast of the Atlantic,the northern area of the North Atlantic drift,and the northern area of the equator in the Atlantic.It is also significant positive correlation with Pacific Decadal Oscilliation(PDO).Mode EOF1 is closely related with the multiple interdecadal variation of sea-air system in the Northern Hemisphere,and at the same it is influenced by global warming.