Collaborative Research: Investigating the Zonal Mean Atmospheric Circulation Changes under Global Warming and the Linkage to the Hydrological Response and Extremes

在温室气体浓度持续增长的气候强迫下，全球大气环流和水文循环必然发生变化。尽管大气环流在气候变化和气候反馈中发挥着关键作用，但我们对大气环流的自然变率、对全球变暖强迫的响应及其对降水时空分布的相关影响的认识仍然有限，部分原因是由于整个年周期背景风配置的多样性。本项目旨在全面了解整个年周期大气环流对温室气体变暖强迫响应的敏感性和机制，并将环流变化与降水平均和极端变化联系起来。研究人员将结合有目的地设计的大气模式层次敏感性实验，分析政府间气候变化专门委员会（IPCC）耦合模式比对项目第5阶段（CMIP5）模式模拟，一套新的超高分辨率气候模拟以及现有的观测和再分析。它们将围绕三个相互关联的科学主题：(1)不同环流体制下（对应于全球不同季节和不同地区）平均环流对全球变暖强迫响应的敏感性和机制；(2)不同环流体制下的主导变率模态及其非强迫内在变率模态与全球变暖强迫平均响应之间的联系；(3)自然或气候变化强迫导致的变率主导模态与降水极端指纹的关联。这项工作将提高我们对以下方面的认识：(1)大气环流的特征以及变率的平均模态和领先模态之间的关系；(2)全球不同区域环流响应的季节依赖性；(3)水文循环及其极值对温室气体变暖响应的机制解释。更广泛的影响包括以下几个方面：(1)在区域水文预测中获得的信心对水资源管理和水政策制定有价值；(2)两所院校的若干研究生和本科生将接受培训并广泛参与；(3)本项目的建模输出将被归档到美国国家大气研究中心（NCAR）“面向社区”的高性能存储系统（HPSS）存档服务系统中，以促进数据与更广泛的科学社区共享。

Under the climate forcing of the unabated growth of the concentration of greenhouse gases (GHGs), the global atmospheric circulation and hydrological cycle are bound to change. Despite the pivotal role of the atmospheric circulation in climate change and climate feedback, our understanding in its natural variability, its response to global warming forcing, and the associated impacts on the temporal and spatial distributions of the precipitation remains limited, due in part to the diversity of the background wind configurations throughout the annual cycle.This project aims to develop a comprehensive understanding of the sensitivities and mechanisms of the atmospheric circulation response to GHG warming forcing throughout the annual cycle, and to link the circulation changes to the changes in the mean and extremes of precipitation. The investigators will combine purposefully designed sensitivity experiments using a hierarchy of atmospheric models with analyzing the Intergovernmental Panel on Climate Change (IPCC) Coupled Model Intercomparison Project Phase 5 (CMIP5) model simulations, a new set of ultra-high resolution climate simulations and the existent observations and reanalysis. They will revolve around three inter-related scientific themes: (1) sensitivities and mechanisms of the mean circulation responses to global warming forcing under different circulation regimes (corresponding to different seasons and different sectors of the globe); (2) the leading mode of variability under different circulation regimes and the linkage between the unforced intrinsic mode of variability to the mean response to global warming forcing; (3) connection between the leading mode of variability, as occurs naturally or as a result of climate change forcing, and precipitation extreme fingerprint. This work will improve our understanding of (1) characteristics of atmospheric circulation and the relationship between the mean and the leading mode of variability; (2) the seasonal dependence in the response of the circulation over different sectors of the globe; (3) mechanism-based interpretation of the response of hydrological cycle and its extremes to GHG warming. Broader impacts encompass the following aspects: (1) The confidence gained in regional hydrological projection is valuable to water resource management and water policy making; (2) Several graduate and undergraduate students from two institutions will be trained and extensively involved; (3) Modeling outputs from this project will be archived in the "community-oriented" High Performance Storage System (HPSS) archive service system at National Center for Atmospheric Research (NCAR) to facilitate the sharing of the data to broader scientific communities.