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Why Do We have El Niño?
来源:LASG    访问次数:    报告时间:2017-9-27
【报告人】        Dr. De-Zheng Sun
【报告人单位】University of Colorado, U.S.
【报告时间】    2017年9月27日(星期三)14:30
【报告地点】    科研楼303会议室
【报告简介】    El Niño, due to its global impact on weather patterns, ecosystems, agriculture and public health, has become as commonly known to the public as global warming. But why we have El Niño is not yet as well answered as it may have been assumed. A nonlinear theory for ENSO has suggested that there exist two equilibrium states for the tropical Pacific—one is zonally symmetric (or nearly so) with the warm-pool extending all the way to the eastern Pacific, and the other is strongly zonally asymmetry with the warm-pool confined to the western half of the tropical Pacific. ENSO results from the fact that under current radiative forcing, both states are unstable, resulting in the apparent “wandering” behavior in between these two states as seen in the observations. Here we obtain the best approximates for two equilibrium states empirically using ocean assimilation data, and quantify the stability of these two empirically obtained equilibrium states using two methods. We find that the two states are indeed unstable, offering support for the nonlinear view of why we have El Niño. Using the same methods, we have also quantified the rectified effect of ENSO on the decadal background state. We have found that the rectified effect of ENSO indeed tends to neutralize the decadal background state, offering additional support for this nonlinear view of why we have El Niño, as well as support for the suggestion that the rectified effect of ENSO may play a critical role in the tropical Pacific decadal variability.
 
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