摘要:北半球环状模(Northern Hemisphere Annular Mode, NAM)是北半球冬季最主要的环流系统，其变化对北半球的冬季气候变率具有重要的影响。现有研究多采用相关、合成等统计方法对NAM及气候要素进行研究，鲜少从因果关系的角度来进行分析。本文基于收敛交叉映射（Convergent Cross Mapping, CCM）算法，利用1960～2018年美国气候预测中心（Climate Prediction Center, CPC）的NAM指数、NCEP/NCAR再分析资料，分析了NAM与东北亚地区冬季地面气温（Surface Air Temperature, SAT）的因果关系的年际变化及其可能的物理机制。结果表明：1）NAM对东北亚地区冬季SAT具有单向因果关系，且其关系的强弱存在年际变化，2006年、1982年分别为因果影响的最大值和最小值年。2）冬季NAM指数存在显著的8～9年尺度主周期，该周期为冬季NAM影响东北亚地区SAT的驱动因子，其变化在一定程度上影响了NAM对东北亚地区SAT因果关系的年际变化。3）对比NAM对SAT影响的因果关系的最大值（2006年）和最小值（1982年）年环流形势，可见，高值年（2006年）NAM的“跷跷板”结构明显，而低值年（1982年）NAM的南北振荡形势并不明显。本文对于分析因果关系的年际、年代际变化给出了一个新的思路。
关键词:北半球环状模（NAM）/
收敛交叉映射算法/
因果关系
Abstract:The Northern Hemisphere Annular Mode (NAM) is the main circulation mode in the Northern Hemisphere in winter, with a significant impact on the winter climate variability in the Northern Hemisphere. There are a number of studies that use statistical methods such as correlation analysis and synthetic analysis to discuss NAM and other climatic factors but rarely with the perspective of causality. In this research, the authors apply the Convergent Cross Mapping (CCM) method and use the NAM index provided by the Climate Prediction Center (CPC) from 1960 to 2018 as well as reanalysis data provided by NCEP/NCAR to analyze the impact of NAM on the winter Surface Air Temperature (SAT) in Northeast Asia. Causality changes its strength and weakness year by year and its possible physical mechanism. Our analysis indicates the following: 1) NAM has a one-way causal relationship with the winter SAT in Northeast Asia, and the strength of the relationship has interannual changes. The maximum and minimum years of causal effects are 2006 and 1982, respectively. 2) The winter NAM index has a significant 8?9-year scale main cycle, which is the driving factor for the winter NAM to affect the SAT in Northeast Asia, and to some extent, its change has affected the interannual change of NAM on the SAT causality in Northeast Asia. 3) Comparing the circulation situation of the maximum (2006) and minimum (1982) years of the causal relationship of the impact of NAM on the SAT, it can be seen that the “seesaw” structure of NAM in the year of maximum causality (2006) is obvious. However, the form of NAM’s north–south oscillation in the year of minimum causality (1982) is not obvious. This work may therefore provide a new idea in analyzing the interannual and inter-decadal changes of causality.
Key words:Northern Hemisphere Annular Mode (NAM)/
Convergent Cross Mapping method/
Causality
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