ENSO十年际尺度变率的机制初探

利用太平洋次表层海温、热含量和洋表风应力等资料探讨了ENSO十年际尺度变率的可能机制。结果表明，热带西南太平洋不仅是年代际信号的显著区，同时也有可能是影响ENSO循环十年际变化的关键区。热带西南太平洋的海温暖异常经热带中太平洋东传到热带东太平洋，导致热带东太平洋产生暖的海温异常，这种海温异常进而激发了澳大利亚东部沿岸的大气，产生反气旋性风应力异常。在这种风场的作用下，其下方海水向四周辐散，使热带西南太平洋的温跃层变浅，产生负的温度异常，此后发生反位相的循环。整个循环过程所需的时间约为13a。

POSSIBLE MECHANISMS OF ENSO'S DECADAL VARIABILITY

Possible mechanisms of ocean-air system in the tropical Pacific are investigated by using upper ocean temperature, heat storage and wind stress data. The main results are as follows. The western tropical South Pacific, where there is an evident decadal variability, is the key region of the ENSO decadal variability. The positive temperature anomaly can move to the mid-tropical Pacific, then propagates eastward to the eastern tropical Pacific and change the original negative temperature anomaly there. If a decadal positive temperature anomaly occurs in the eastern tropical Pacific, the atmospheric response will excite an anti-cyclonic wind stress anomaly in the east of Australia, which will lead to the generation of a negative temperature anomaly in the western tropical South Pacific. A similar evolution with an opposite sign will follow subsequently. The whole cycle needs about 13 years.