The Impact of Arctic Amplification on the Midlatitude Circulation: Non-linearity and Non-additivity

北极海冰损失和北极表面快速变暖（与北极放大有关）对北方半球大气环流的影响尚未完全了解。随着海冰的减少，对大气环流、急流和极端天气事件的影响是否会加剧？不同北极地区的海冰损失是否使北极放大的影响复杂化？该提案解决了这些问题，旨在促进目前对北极海冰融化和北极放大对高影响极端天气的影响的理解。新的成果可以提高这些极端事件的可预测性，这些极端事件对运输和能源生产实践的规划和管理具有重大的社会影响。该项目将培训和支持一名研究生和两名本科生暑期实习生，后者通过一个暑期项目，重点是招募代表性不足和社区大学的学生。调查小组假设：（1）大气阻塞和极端天气对北极海冰损失和变暖的反应是非线性的：当北极强迫强度较小时，阻塞的频率和局地持续性随强迫强度的增加而增加，而当强迫强度变大时，阻塞随强迫强度的增加而减少;（2）北极海冰融化的响应不具有线性可加性，由于非线性的波-平均流相互作用，非可加性分量显著。拟议的任务将测试这些假设在一个层次的模型，从一个简单的干动力学表示到一个国家的最先进的大气环流模型。它将评估非线性和非可加性的鲁棒性，并使用新的诊断方法（如局部有限振幅波活动）检查潜在的动力学机制。这项研究将提供一个系统的和过程为导向的动态了解大尺度大气环流模式的变化，在大气阻塞和极端天气，并促进未来的劳动力和多样性的研究领域的气候和大规模气候变化。该奖项反映了NSF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进行评估，被认为值得支持审查标准。

The impact of Arctic sea-ice loss and rapid surface warming over the Arctic (associated with Arctic Amplification) on the atmospheric circulation in the Northern Hemisphere is not fully understood. As the sea-ice loss worsens, does the effect on the atmospheric circulation, jet stream, and extreme weather events intensify? Does the different sea-ice loss over various Arctic regions complicate the influence of Arctic Amplification? This proposal addresses these questions and aims to advance the current understanding of the impact of the Arctic sea-ice melting and Arctic Amplification on high-impact weather extremes. The emerging results can improve the predictability of these extreme events that have significant societal impacts in the planning and management of transportation and energy production practices. The project will train and support a graduate student and two undergraduate summer interns, the latter through a summer program focused on the recruitment of underrepresented and community college students.The investigative team hypothesizes that (1) atmospheric blocking and weather extremes respond to Arctic sea ice loss and warming non-linearly: when the Arctic forcing magnitude is small, the frequency and local persistence of blocking increases with forcing; however, as the forcing magnitude becomes large, blocking decreases with forcing; (2) responses to regional Arctic sea ice melting are not linearly additive and the non-additivity component is significant due to the nonlinear wave-mean flow interaction. The proposed tasks will test these hypotheses in a hierarchy of models ranging from a simple dry dynamics representation to a state-of-the-art atmospheric general circulation model. It will assess the robustness of non-linearity and non-additivity and examine the underlying dynamical mechanism using novel diagnostics such as the local finite-amplitude wave activity. The research will provide a systematic and process-oriented dynamical understanding of the large-scale atmospheric circulation patterns underlying the changes in atmospheric blocking and weather extremes and promote the future workforce and diversity in the research area of climate and large-scale dynamic.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.