Dynamics and Predictability of Extratropical Vortices

对流层顶涡是高纬度地区普遍存在的特征。虽然其中一些涡旋，如切断气旋，与温带气旋形成和罗斯比波破碎有关，但其他涡旋似乎独立于这些过程而发生。特别是在北极上空，涡旋发生在温带急流的极地方向，是较大的环极涡旋内部的一个决定性特征。对北极涡旋的形成和增强缺乏解释，这些问题构成了研究的基础。该研究的第二个重点涉及包含这些涡旋的更大规模流动的可预测性。关于涡旋强度变化的关键假设将通过观测和模拟两种方法进行验证，这些假设是：(1)辐射冷却负责饱和北极涡旋的核心，并且这一过程对涡旋动力学很重要；(2)对流层顶附近较弱的稳定性可能使与凝结有关的最大潜热水平向上移动到更靠近动力对流层顶；(3)辐射对极冷涡旋的潜热起主导作用，对较暖涡旋的潜热起主导作用。模拟策略将用于系统地检验辐射和潜热对对流层顶涡旋动力学反馈的假设。智力优势：PI将(1)使用观测和建模方法测试关于涡旋强度变化的关键假设；(2)利用观测工作确定大样本涡旋强度变化的大尺度模式；(3)将使用数值模型模拟和基于集成的状态估计技术检查个别情况。更广泛的影响：这项研究将提高我们对极地涡旋的理解，并增加对中纬度天气的可预测性。研究生和本科生将接受极地涡旋观测和建模分析方面的培训。

Tropopause vortices are ubiquitous features at high latitudes. While some of these vortices, such as cut-off cyclones, are related to extratropical cyclogenesis and Rossby wave breaking, others appear to occur independently of these processes. In particular, over the arctic, vortices occur poleward of the extratropical jet streams and are a defining characteristic of the interior of the larger circumpolar vortex. Explanations for arctic vortex origination and intensification are lacking, and these issues form the basis for the research. A second thrust of the research concerns the predictability of the larger-scale flows that contain these vortices. Key hypotheses regarding vortex intensity changes will be tested using both observational and modeling approaches and these are: (1) radiative cooling is responsible for saturating the core of arctic vortices, and that this process is important for the vortex dynamics; (2) weaker stability near the tropopause may allow the level of maximum latent heating associated with condensation to move up closer to the dynamical tropopause; and (3) radiation may dominate latent heating for very cold vortices, and latent heating may dominate for warmer vortices. Modeling strategy will be applied to systematically test the hypotheses regarding the feedbacks of radiation and latent heating on tropopause vortex dynamics. Intellectual Merit: The PI will (1) test key hypotheses regarding vortex intensity changes using both observational and modeling approaches; (2) use observational work to determine the large-scale patterns associated with vortex intensity changes for a large sample of cases; and (3) will examine individual cases using numerical model simulations and ensemble-based state estimation techniques. Broader Impacts: The research will improve our understanding of the polar vortices and also increases the predictability of mid-latitude weather. A graduate and undergraduate student will be trained in the observational and modeling analysis of polar vortices.