北赤道流区海温异常与ENSO循环

ANOMALOUS SEA TEMPERATURE OF WESTWARD TRANSFERRING NORTH EQUATORIAL CURRENT AND ENSO

应用热带太平洋上层XBT温度资料,分析探讨了西太平洋暖池区次表层海温冷暖异常信号的变化规律,揭示了影响西太平洋暖池区次表层海温冷暖异常信号的机制。分析表明,西太平洋暖池区的次表层海温异常冷暖与太平洋北赤道流的海温冷暖异常信号西传有重要关系。北赤道流的海温异常冷(暖)信号是沿温跃层由赤道中东太平洋潜沉向西太平洋暖池区传播,对暖池区域次表层海温场产生重要影响。这一传播过程与西太平洋次表层海温异常暖(冷)信号向赤道中东太平洋传播,构成了热带海洋信号的气旋式“信号通道”。在这一“信号通道”中,北赤道流的海温异常信号西传是导致西太平洋暖池区及西太平洋次表层海温异常的重要机制,是影响El Nino和 La Nina事件发生的关键。

Based on XBT temperature data during 1955 -- 1999 in the tropical Pacific, the regularity and its formation mechanism of the warm and cold anomalous signals of the sub-surface sea temperature in the warm pool region of the western Pacific, which plays an important role to the El Nino and La Nina events occurred in the western Pacific, are analyzed and discussed. The analysis indicates that the sub-surface anomalous warming and cooling in the western Pacific warm pool has a close relationship with the tempera- ture anomalies of the northern equatorial current (10°N ). At the earlier stages of El Nino and La Nina events, the anomalous warm or cold water located in the equatorial central and eastern Pacific subducts toward the warm pool region of the western Pacific along thermocline of the northern equatorial current, then piles up in the warm pool re- gion and expands toward the equatorial western Pacific. The warm or cold water trans- ported eastward to the equatorial central and eastern Pacific will float to the sea surface along the sloping thermocline under the forcing of atmosphere. When anomalous warm or cold water achieves certain strength, it will finally lead to the eruption of El Nino and La Nina events. The anomalous temperature signals propagating westward in the north- ern equatorial current and eastward in the equator have formed cyclonic 'signal pathway' along thermocline in the tropical ocean. The 'signal pathway' is the key mechanism lead- ing to ENSO episodes.