近百年中国两次年代际气候变暖中的冷、暖平流背景

The background of cold/warm advection for two interdecadal warming processes during the last century in China

近百年中国气候经历了两次明显的年代际变暖,分别发生在20世纪40年代之前和70年代之后。由大气环流变化引起的冷、暖平流异常可为理解两次变暖提供参考。首先基于最新研制的近百年32站气温观测和集合经验模分解(Ensemble Empirical Mode Decomposition,EEMD)方法揭示两次变暖过程中国的冷、暖分布格局,进而利用全球格点气温和海平面气压资料计算了同期地转风导致的温度平流。结果表明,20世纪40年代中国华北北部至东北大部分地区和华南沿海局部地区偏冷而中东部至西南内陆大部分地区偏暖的年代际气候异常,站点冷、暖异常与大尺度温度平流的空间关联系数达0.85;而对于近20年中国气候变暖而言,这一关联系数仅0.49。研究结果从一个新颖的角度说明:早期变暖过程中气候系统内部过程如大气环流异常的作用较大,而近几十年气候变暖则更多地受迫于外强迫。

During 20 century, there were two notable decadal warming processes in China that occurred before the 1940s and af ter the 1970s, respectively. An analysis of temperature advection associated with the atmospheric circulation is helpful for better understanding the regional warming processes. This paper firstly analyzes homogenized long-term temperature observations collected at 32 stations in China using the ensemble empirical mode decomposition （EEMD） method and reveals the geographical pattern of temperature anomalies around the 1940s. It is found that at the interdeeadal timescale, cold anomalies occurred in northern North China, Northeast China and part of southern coast, while warm anomalies occurred in most of other areas in China around the 1940s. Similar results are obtained based on the CRU （Climatic Research Unit） global gridded temperature data. Secondly, the temperature advection around the same time period based on gridded temperature and sea level pressure da ta is calculated. The spatial corresponding coefficient between temperature anomalies at the stations and the large scale temper ature advection is as large as 0.85. In contrast, the coefficient between them during the recent warming period is 0.49. The re- suits indicate from a novel point of view that the internal climate variability associated with the atmospheric circulation might play a more important role in the earlier warming process in China in the 1940s, but the recent warming progress after the 1970s could be more due to external thermal forcing.