Collaborative Research: Revisiting the Low-Frequency Variability of the Extratropical Circulation Using Non-Empirical Orthogonal Function (EOF) Modes and Linear Response Functions

两半球温带对流层大气环流变率的一个主要模式是强弱西风急流之间的振荡，其时间尺度大于10天。这种温带西风急流的低频变率被称为环状模态。年模态影响着中高纬度地区的日常天气和极端事件，因此具有很大的研究价值。冬季半球的环状模态也影响平流层极涡，并受其影响。该项目旨在更深入地了解控制环空模式的因素。这项工作的结果将有可能改变对中高纬度急流变异性和天气的理解。该结果还可能导致可预测性的进步，超过目前大约10天的天气预报障碍，并导致气候模式能力的改进。此外，新的定量框架将有助于解释综合气候模式预测的一系列结果。这些成果有可能推动国家和全球为应对气候变化和与天气有关的极端事件所做的努力，从而产生重大的社会经济效益。该项目将支持两名博士生和一名博士后的教育和培训，从而为下一代大气动力学家和气候科学家做好准备。在这项工作中开发的一些工具将被pi在他们的本科和研究生水平的教学中使用，以帮助学生可视化和量化急流变率的某些方面。此外，该项目将通过赖斯大学和斯坦福大学的几个STEM外展项目，让K-12学生参与气候和计算机建模相关的研究。在这个项目中，将开发新的分析方法，并将与计算机模型和观测数据一起使用，以更深入地了解喷射流的这种变化。此外，将制定一个新的框架，以定量地将目前的这种可变性与未来的可变性联系起来。该框架将整合急流变率和极涡对各种气候强迫的响应，如温室气体增加或臭氧消耗。该项目的具体任务是：1)在观测和气候模式中研究正压和斜压环模之间的耦合；2)建立环形模态传播的涡流反馈模型；3)利用数值实验了解平流层对两个半球对流层环状模态的影响；4)研究气候模式模拟中的低频变率模态和波动-耗散关系，以更好地评价气候模式模拟中气候变化预估的保真度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

One dominant pattern of the atmospheric circulation variability in the extratropical troposphere of both hemispheres is the oscillation between stronger and weaker westerly jet streams with a time scale longer than 10 days. Such low-frequency variability of extratropical westerly jet streams is called the annular mode. The annual mode influences the day-to-day weather and extreme events in the middle and high latitude regions and is therefore of great interest to understand. The annular mode in winter hemisphere also influences, and is influenced by, the stratospheric polar vortex. This project seeks a deeper understanding of the factors that control the annular mode. The outcome of this work will potentially transform the understanding of jet stream variability and weather in the middle and high latitudes. The outcome could also lead to advances in predictability past the current weather prediction barrier of about 10 days, and lead to improvements in capabilities of climate models. Furthermore, the new quantitative framework will aid the interpretation of the range of outcomes predicted by comprehensive climate models. These outcomes have the potential to advance the national and global efforts aimed at preparing for climate change and weather-related extremes, resulting in significant socio-economic benefits. This project will support the education and training of two PhD students and a postdoctoral researcher, thus preparing the next generation of atmospheric dynamists and climate scientists. Some of the tools developed during this work will be used by the PIs in their undergraduate and graduate-level teaching to help the students with visualizing and quantifying some aspects of the jet stream variability. Also, the project will engage K-12 students in climate and computer modeling-related research through several STEM outreach programs at Rice and Stanford.In this project, novel analysis methods will be developed, and will be employed along with computer models and observational data to gain a deeper understanding of this variability of the jet streams. Furthermore, a new framework will be developed to quantitively link this variability in the present day to variability in the future. This framework will integrate the response of the jet stream variability and polar vortex to various climate forcings, such as greenhouse gas increase or ozone depletion. The specific tasks of this project are 1) examining the coupling between the barotropic and baroclinic annular modes in observations and in climate models; 2) developing an eddy feedback model for propagating annular modes; 3) understanding stratospheric influence on the tropospheric annular mode in both hemispheres using numerical experiments; 4) studying low-frequency variability modes and fluctuation-dissipation relationship in climate model simulations to better evaluate the fidelity of the climate change projections in these simulations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.