Modeling and Observational Study of Decadal El Nino-Southern Oscillation (ENSO) Modulation and Tropical Pacific Decadal Variability

厄尔尼诺-南方涛动（ENSO）现象提供了年际时间尺度上气候可预测性的重要来源。本研究旨在通过模式试验和观测分析，对ENSO年代际调制和热带太平洋年代际变率的重要过程进行机制理解。假设南北太平洋随机大气变率的低频分量，即北太平洋涛动（NPO）和太平洋-南美（PSA）变率，独立驱动热带太平洋年代际变率。此外，NPO驱动的热带太平洋年代际变率与ENSO相互作用，并通过平均热带辐合带（ITCZ）的经向位移调节其振幅。另一方面，PSA变率驱动了与太平洋年代际涛动（PDO）相关的enso样年代际变率，影响了南太平洋辐合带（SPCZ）的降水。这些假设将通过气候和大气模式实验的详细分析得到验证。模式结果还将通过对过去100-200年各种仪器数据和古气候代理记录的观测分析进行验证。观测分析将显示ITCZ和SPCZ是否在年代际时间尺度上独立变化，以及它们的年代际变化如何与年代际ENSO调制相关。该项目获得的结果不仅将揭示热带太平洋气候变率的本质，而且还将为理解未来ENSO行为的不确定性和解释ENSO的古气候代理记录提供指导。

The El Nino-Southern Oscillation (ENSO) phenomenon provides an important source of climate predictability on interannual time scales. The research aims for mechanistic understanding of the processes important to the decadal modulation of ENSO and tropical Pacific decadal variability through model experiments and observational analysis. It is hypothesized that the low frequency components of stochastic atmospheric variability in the North and South Pacific, namely, the North Pacific Oscillation (NPO) and Pacific-South American (PSA) variability, independently drive tropical Pacific decadal variability. Furthermore the tropical Pacific decadal variability driven by NPO interacts with ENSO and modulates its amplitude through meridional displacement of the mean intertropical convergence zone (ITCZ). The PSA variability, on the other hand, appears to drive ENSO-like decadal variability associated with the Pacific Decadal Oscillation (PDO), affecting precipitation in the South Pacific convergence zone (SPCZ). These hypotheses will be tested through detailed analysis of climate and atmospheric model experiments. The model results will also be validated with observational analysis of various instrumental data and paleoclimate proxy records for the past 100-200 years. The observational analysis will show if the ITCZ and SPCZ vary independently on decadal-interdecadal time scales and how their decadal variability is associated with the decadal ENSO modulation. The results obtained from the project will not only shed light on the nature of tropical Pacific climate variability but also provide guidance in understanding the uncertainty of future ENSO behavior and in interpreting paleoclimate proxy records of ENSO.