1970s中期全球气温关联网络结构特征的变化研究

The adjustment of structure characteristics of the global temperature correlation network in the Mid-1970s

气温关联网络结构特征分析是当前气候系统复杂网络研究领域的热点科学问题,相关研究成果对于深入认识气候系统的复杂性和内部相互作用等具有重要的科学意义.为深入探究气温关联网络结构的时间演化特征,本研究尝试构建偏冷态和偏暖态对应的气温关联网络,揭示1970s中期气温关联网络结构的变化及其可能成因.研究结果表明,气温关联网络连通性在1970s中期由偏冷态强于偏暖态转变为偏暖态强于偏冷态,且这种变化在赤道中东太平洋等低纬度大洋关键区域尤为显著.1970s中期之后,偏冷态对应的热带大西洋、印度洋等关键区域的气温距平由负相位调整为正相位,造成其与赤道中东太平洋区域之间的气温协方差为负值的概率显著增加,相关系数减小,网络联通性显著减小;偏暖态则对应关键区域气温距平维持正位相为主,气温协方差为正值概率高,相关系数略增大,网络连通性略有所增加.此消彼长,造成1970s中期之后气温关联网络结构特征出现偏暖态网络连通度强弱对比的反转.去除全球增暖对应的线性趋势后,偏冷态和偏暖态之间的网络连通度差异明显减小,1976年前由13.1%下降到-1.7%,1976年后由-37.0%下降到-8.2%.因此,全球增暖趋势通过改变全球不同区域的气温距平正负位相,进而造成网络连通度强弱对比的反转,即全球增暖不仅简单表现为气温的总体上升,更会引起气候系统内部网络结构特征的调整.

The analysis of the temperature correlation network is a hot topic of current climate complex network field,which is of great help to better understand the complexity and the internal action of climate system.In order to discuss the evolution feature of the network structure,this study set up the global temperature correlation network(GTCN)based on the cold and warm phase data of global surface temperature,reveal the adjustment of structure characteristics of GTCN and attribute the probable reason.Study results indicate that the network connection changed from the state of cold phase being higher than warm phase to the opposite state in the mid-1970s,which is especially obvious in the low latitude regions.After the mid-1970s,temperature anomalies corresponding to the cold phase change from negative values to positive ones over tropical Atlantic and Indian Ocean,making the temperature covariances among key regions change from positive to negative values,causing the decrease of correlations of temperature series among key regions,leading to the decrease of the network connections in cold phase.Meanwhile,temperature anomalies corresponding to the warm phase keep positive values and even have weak increase over tropical oceans,making the temperature covariances among key regions remain positive,correlations show weak increase,causing the network connections have small increase.The decrease of network connections in cold phase and increase in warm phase after mid-1970s,lead to the shift of network connections after the mid-1970s.Besides,after removing the linear warming trend from the temperature series,the network connections show obvious decrease.The difference of network connections between cold and warm phase respectively decreased from 13.1%to-1.7%and from-37.0%to-8.2%before and after mid-1970s.Therefore,the global warming plays a quite important role in influencing the shift of the network connection after the mid-1970s,which implies the global warming not only presents the rise of overall temperature,but also may cause the change of internal structure of the climate system.