前期热带太平洋次表层海温异常与东亚夏季风的可能联系

利用1979—2012年日本气象厅次表层海温资料和NCEP/NCAR再分析资料,分析了前期冬季热带太平洋次表层海温与东亚夏季风的关系,并讨论了其可能机制。结果表明,前期冬季热带太平洋次表层海温与后期东亚夏季风强弱有显著的相关关系。冬季次表层海温呈现东正西负的类El Nio分布型时,夏季副热带高压偏强,西北太平洋地区受反气旋型环流控制,能将大量的水汽输送到长江和淮河流域,有利于水汽在该区域辐合,为夏季降水偏多创造了条件,此时东亚夏季风活动整体偏弱,反之亦然。但类El Nio分布型对东亚夏季气候变化的影响较类La Nia分布型更显著。此外,冬季热带太平洋次表层海温可能通过其自身能够持续性地影响东亚—太平洋地区的大气环流异常,次表层海温随季节变化有明显的发展和移动趋势:冬季西太平洋暖池次表层冷(暖)海温不断堆积,沿温跃层向东传播使得中东太平洋次表层海温逐渐变冷(暖),冷(暖)海温上翻加强使得海表温度异常,进一步影响到西太平洋副热带高压的位置和强度,并在东亚地区形成经向遥相关波列,通过西北太平洋地区异常反气旋(气旋)环流的作用,影响东亚地区大气环流以及气候变化。

A strong correlation between Pacific subsurface ocean temperature and East Asian summer monsoon

In this study,based on the output of historical ocean temperature analysis program conducted by Japan Meteorological Agency and NCEP/NCAR reanalysis project,a relationship between tropical Pacific Subsurface Ocean Temperature Anomalies(SOTA) and East Asian Summer Monsoon(EASM) is proposed and investigated.The results indicated that there is a strong correlation between SOTA during winter and EASM.Among the three leading modes in the tropical Pacific subsurface temperature,the first mode has a dipole pattern,with warming in the eastern Pacific and cooling in the western Pacific,which is closely related to traditional El Niño,the western Pacific subtropical high(WPSH) is enhanced.An anomalous anticyclone with its southwesterly winds dominating over the western North Pacific,carrying abundant moisture to Yangtze River and Huaihe River Basin as well.Subsequently,it favors a positive precipitation anomaly along with a poor EASM,which in comparison with traditional El Niño,demonstrating that the impact of traditional El Niño is more significant than the EASM.The persistence of SOTA during winter could lead to form sustainable effects,affecting the general circulations over East Asian Pacific.When a continuous negative(positive) SOTA in the warm pool moves eastwards,the Sea Surface Temperature(SST) of East Pacific becomes cold(warm),while the strengthening of overturning due to the temperature of cold(warm) sea causes anomalies in the SST.Consequently,a meridional wave train appears over East Asia in the summer.Under the impact of an anomalous Western North Pacific anticyclone,it highly affects the atmospheric circulation and climate as well.