中国东北地区冬季气温趋势及反相模态分析

利用1951—2010年我国东北地区共97个台站的逐月气温资料,应用trend-EOF和EOF分析方法研究了我国东北地区冬季气温的趋势模态和反相模态及其影响因子。trend-EOF的结果表明,东北地区均为一致型的趋势变化,trend-PC1有明显的年代际周期变化和更长期的上升趋势变化特征。去除全球变暖信号后的EOF分析结果表明:第一模态仍为全区一致型的空间分布,而第二模态的空间分布呈现南北反相型的分布特征,是东北冬季气温变化模态中极为重要的一部分,对应的时间序列有明显的年际周期变化,前两个模态可以解释总方差80%以上的变化。东北地区全区一致的上升趋势是在全球变暖大背景下发生的,既是对全球变暖的局地响应,同时全球变暖也使大气环流发生了变化,西伯利亚高压减弱,纬向环流增强,导致了东北地区冬季气温全区的上升趋势。赤道东太平洋的异常海温对第二模态的出现具有一定的预示意义,当太平洋出现典型的厄尔尼诺年海温距平场分布特征时,东北南部较常年偏暖,北部地区却较常年偏冷。

Analysis of trend pattern and seesaw pattern of winter temperature in Northeast China

Based on the mean monthly temperature data of 97 stations during 1951 to 2010 in Northeast China, the methods of trend Empirical Orthogonal Function (trend-EOF) and Empirical Orthogonal Function (EOF) were used to analyze the trend pattern and seesaw pattern of winter temperature and its influencing factors. The trend-EOF results show that a consistent trend variation existed over Northeast China, and trend-PC1 has distinct interdecadal periodic variation and a longer-term uptrend variation. The EOF results derived after removing global warming signal show that the first EOF mode depicts a consistent region-wide spatial distribution, while the second EOF mode describes a temperature inverted distribution between northern and southern part of the region. These two modes can explain over 80% variance. Under the background of global warming, the first mode of EOF is not only a local response to global warming but a positive response to the variation of low latitude Sea Surface Temperature (SST) over Indian ocean correlated with the global warming. Meanwhile, the global warming may change general atmospheric circulation, weaken the Siberian high pressure, and intensify the zonal circulation, which all lead to the rising of temperature in Northeast China. It is suggested that the tropical eastern Pacific SST anomalies can predict the appearance of the second mode. When the typical El Niño happens, the temperature in the south of northeastern China would rise and in north it would fall.