北大西洋两种年代际海温模态对平流层环流和温度的影响及机理研究

Interdecadal climate change and variability is a cutting-edge and hot topic of the atmospheric science research. There is a strong dynamical coupling between the stratosphere and the troposphere. Therefore, in order to have a comprehensive understanding of the interdecadal changes occurring in the climate system, it is necessary to study the interdecadal variations in the stratosphere and its interaction with the troposphere. Many previous studies have investigated the impacts of the variations of sea surface temperature (SST) on the stratosphere, but much less attention has been paid to the impacts at the interdecadal timescales. The North Atlantic is one of the regions on the globe where the most pronounced interdecadal variability is observed, but there is still a lack of systematic understanding of its impact on the stratosphere and the associated mechanisms. Recent studies have demonstrated that the interdecadal variability of the North Atlantic is dominated by two decadal SST modes: the Atlantic multidecadal oscillation (AMO) and the decadal North Atlantic SST tripole (DNAT). Therefore, this project will focus on these two decadal SST modes and their impacts on the stratosphere. By using the long-term observation data sets and model outputs, employing statistical analysis and dynamic diagnosis method, and combing with the theoretical analysis, theoretical model and numerical simulations, we expect to study the influences of AMO and DNAT on the interdecadal variations of stratospheric atmospheric circulation and temperature, to clarify the key roles of stratosphere-troposphere dynamical coupling and three-dimensional propagation of quasi-stationary planetary waves, to reveal the physical processes and mechanisms involved in the influences of AMO and DNAT on the stratosphere, to make clear the differences and linkages between the two SST modes, and finally to establish a physical conceptual model for the impact of North Atlantic interdecadal oscillations on the stratosphere.

年代际气候变化是大气科学研究的前沿和热点。平-对流层之间存在强的动力耦合，因此，要全面认识和理解气候系统中发生的年代际变化，就必须深入研究平流层在年代际尺度的演变特征及与对流层相互作用的机理。以往关于海温对平流层的影响已有很多研究，然而关注年代际尺度的工作还较少。北大西洋是全球海温年代际变率最强的地区之一，但是目前关于它对平流层的影响及机理尚缺乏系统认识。最近的研究表明，北大西洋年代际变率主要由大西洋多年代际振荡(AMO)和年代际三极子海温型(DNAT)所控制。因此，本项目将从这两种海温模态入手，利用长期的观测、模式资料，通过资料统计和动力诊断，结合理论分析及数值模拟，研究AMO和DNAT对平流层环流和温度年代际变化的影响，揭示平-对流层耦合和行星波三维传播在其中的关键作用，阐明AMO和DNAT影响平流层的机制，弄清两者的区别和联系，最终建立北大西洋海温年代际振荡影响平流层的物理概念模型。

北大西洋是全球海洋-大气相互作用最为强烈的地区之一，该地区海表温度的变化不仅会影响对流层的天气气候波动，也会引起平流层环流和温度的变化，对认识全大气层的演变规律有重要影响。以往的研究对北大西洋海表温度的主导模态以及海温变率影响平流层的过程和机制认识不清，限制了对全大气层和海洋相互作用的了解。本项目将基于北大西洋两个海温主导模态，阐明了两个海温模态物理本质的差别及海-气耦合的主要机制，揭示了全大气层对北大西洋海温变率的响应规律，研究了大西洋海温对中高纬大气波动和北极极涡活动的调控作用，揭示了大西洋对北半球区域气候和极端事件的关键影响。项目研究取得的成果对认识大气环流系统变化和理解热带外全大气层-海洋相互作用机制提供重要的理论依据和物理参考，对提高热带外中长期气候预测水平具有重要的指导意义。