基于非平稳响应归因法的ENSO-东亚季风关系年代际变化机理研究

As the predominant signal of the global interannual climate variability, ENSO provides the main source for skillful predictability on the seasonal-to-interannual timescale. However, recent observational studies suggested that the East Asian monsoon responses to ENSO are not stationary on interdecadal timescales. And the underlying physical mechanisms have become an important issue in the research community of climate dynamics. Due to the lack of quantitative diagnosis, the key reason for this phenomenon remains controversial. Using the latest observational and reanalysis datasets, along with a suit of statistical and dynamical diagnosis analyses, this project aims to investigate the decadal nonstationary characteristics of the East Asian atmospheric and climate responses to ENSO events. Based on a newly-developed statistical method for interpreting and attributing nonstationary responses, we expect to quantitatively determine the key source accounting for the interdecadal variations of the ENSO-East Asian monsoon relationship. By carrying out sensitive numerical experiments, the physical mechanisms for the decadal nonstationarity of the ENSO-East Asian monsoon relationship will be unraveled and presented. Implementation of the relevant work will improve the understanding about the long-term variations of ENSO teleconnection, and thus carry important implications for the regional seasonal-to-interannual climate predictability associated with ENSO.

作为全球年际气候变率中的最强信号，厄尔尼诺-南方涛动（ENSO）是探索季节-年际尺度预测最有希望的途径之一。然而近期观测研究指出，ENSO对东亚季风的影响在年代际尺度上存在明显的不稳定性。由于缺少定量诊断，目前科学界对于这一现象的产生原因看法不一。本项目拟利用最新多源观测和再分析数据的动力诊断，考察ENSO年东亚季风异常响应的年代际变化特征，基于一套最新发展的非平稳响应归因法的定量诊断，明确引起东亚季风对ENSO响应年代际变化的关键物理因子，结合气候模式的数值试验，揭示关键因子调控ENSO-东亚季风关系年代际变化的物理机制。项目的实施不仅有利于进一步理解ENSO及其大气遥相关的多尺度变化规律，对于提高区域性短期气候预测水平也具有重要意义。

厄尔尼诺-南方涛动（ENSO）是东亚季节-年际气候预测的主要来源，但近期研究发现，ENSO对东亚季风的影响并不稳定，使得传统的东亚季风预测经验受到严重挑战。本项目旨在利用一套新发展的非平稳响应归因法，对ENSO-东亚季风关系的年代际变化进行定量归因，并探究其中的物理机制。我们研究发现，东亚冬春季大气环流及气候异常对ENSO的响应均存在明显的年代际变化特征。通过应用非平稳响应归因法，我们发现这种年代际变化主要来源于大西洋多年代尺度振荡（AMO）对ENSO大气遥相关的年代际调制。AMO调制作用的物理过程主要包括两个方面。首先，AMO能影响ENSO海温异常的位置和强度，进而改变ENSO-南方降水关系的关系。其次，AMO还能通过改变Walker环流调制ENSO年热带太平洋和印度洋对流响应的强度，进而影响ENSO年东亚地区的大气响应。上述结果对我国短期气候预测具有重要参考意义。