太平洋年代际振荡冷、暖背景下ENSO循环的特征

The Characteristics of ENSO Cycle in Different Phases of Pacific Decadal Oscillation

利用英国气象局哈德莱中心的月平均海温距平资料、美国Scripps海洋研究所联合环境分析中心(JEDAC)的海表和次表层海温观测资料以及NCEP/NCAR再分析资料,研究了太平洋年代际振荡(PDO)不同背景下ENSO循环的特征。结果表明,PDO为ENSO循环提供了一个年代际气候背景,在PDO的暖位相时期,ElNino事件发生的频率较高,强度较强;反之,在PDO的冷位相时期,LaNina事件发生的频率较高,强度较强。而且在不同的太平洋年代际振荡背景下,ENSO循环表现出不同的特征。在PDO冷位相时期,发生ElNino(LaNina)事件时,正(负)的SOTA从西太平洋沿温跃层向东传播,正(负)的SSTA从赤道东太平洋向西扩展到中太平洋,ENSO事件先在赤道东太平洋爆发。在PDO的暖位相时期,发生ElNino(LaNina)事件时,正(负)的SOTA首先出现在赤道中太平洋,然后沿温跃层向东传播,正(负)的SSTA从赤道中太平洋向东扩展到东太平洋,ENSO事件首先在中太平洋爆发。这为ENSO预测提供了新的线索。

The monthly sea surface temperature anomaly of Hadley Centre for Climate Prediction and Research,subsurface ocean temperature data of Joint Environmental Data Analysis Center(JEDAC) and NCEP/NCAR monthly reanalysis dataset are used to demonstrate the characteristics of ENSO cycle in different phases of Pacific Decadal Oscillation (PDO). The results show that PDO provides a interdecadal climatic background for ENSO cycle. The occurrences of El Nio events are relatively higher and the intensity of El Nio is stronger in the warm phase of PDO. On the contrary, the occurrences of La Nia events are relatively higher and the intensity of La Nia is stronger in the cold phase of PDO. Furthermore, The ENSO cycle exhibits different characteristics in different phases of PDO. During the cold phase of PDO, the occurrence of El Nio (La Nio) is characterized by eastward propagation of positive (negative) SOTA in western Pacific along the equatorial thermocline. Concurrently, positive (negative) SSTA extends westward from equatorial eastern Pacific to central Pacific, so that the onset of El Nio (La Nio) happens in equatorial eastern Pacific primely. In the warm phase of PDO, the occurrence of El Nio (La Nio) is characterized by the primal appearance of positive (negative) SOTA in equatorial central Pacific which propagate eastward along the equatorial thermocline then. Meanwhile, the positive (negative) SSTA extends eastward from central Pacific to eastern Pacific. The onset of El Nio (La Nio) takes place in equatorial central Pacific firstly. These results give some new clues for the prediction of ENSO.