ENSO气温关联网络结构特征差异及成因分析

Analysis of structural differences and causes of ENSO temperature network

基于全球地表气温资料,分别构建了El Niño和La Niña事件对应的全球气温关联网络,并分析网络结构特征的差异,探究可能的成因.结果表明,与La Niña事件气温网络(简称La Niña网络)相比,El Niño事件气温网络(简称El Niño网络)中格点温度序列间的相关性减弱,气温网络的连通度显著降低,连通性下降,在热带和南温带区域连通性变化尤为显著.赤道东太平洋、赤道西太平洋、赤道印度洋和赤道大西洋的网络连通度相对较大,在El Niño网络中的减少异常明显,是导致两类网络结构特征差异性的4块关键区域.在此基础上初步探讨了两类网络特征差异的原因,即随着Niño3.4区域的海温升高,赤道东太平洋、赤道印度洋等区域海温升高,对外长波辐射加强,对流活动增加,低纬度与中纬度区域的相互作用增强,南北温带气温变化的方差加大,造成关键区格点气温序列与全球其他地区的相关性减弱,全球格点气温网络连通性下降.

Based on the global surface temperature data,the global temperature correlation networks corresponding to El Niño and La Niña events are constructed respectively,and the differences in their effects on the network topological structure properties are analyzed.The results show that compared with the La Niña temperature network,the correlation between grid temperature series in El Niño temperature network is weakened,and the connectivity of the network is significantly reduced,especially in the tropical region and the southern temperate region.The network connectivity degree of equatorial eastern Pacific,equatorial western Pacific,equatorial Indian Ocean and equatorial Atlantic Ocean are relatively large,and the decrease in El Niño network is notable.They are also the four key regions leading to the differences of the structural characteristics of the two types of network.On this basis,the reason for the difference between the two types of network characteristics is preliminarily discussed.With the increase of SST in Niño3.4 region,the SST in equatorial eastern Pacific,equatorial Indian Ocean and other areas rise,which strengthenes outgoing long wave radiation and convection activities,and the interaction between low latitude and mid-latitude areas,and the variance of air temperature changes in the north and south temperate regions increase.As a result,the correlation between the temperature series of the four key regions and the rest of the world is weakened,therefore the connectivity of the global grid temperature network is reduced.