Lagrangian Flow Boundaries, Transport, and Vortex Cores in Pre-genesis Disturbances

这项研究建立在“有袋动物范式”的基础上，以研究哪些前成因扰动最终成为热带风暴和飓风。 非洲东风波（AEW）临界层流中通常存在有利的环境，作为动力学（风）和热力学（热和水分）支持发展的基本前体环境。 虽然一个受保护的运动环境是必要的发展，通常不到20%的这些波实际上产生飓风。 评估近风暴环境的经典方法使用欧拉框架，在该框架中，风暴在流经固定域时进行研究。 拟议的研究旨在研究这些流量通过使用拉格朗日相干结构（LCS）分析，其中诊断工具遵循空气流入发展中的风暴前环境。 穿过稳定气流的封闭流线的湿气、干燥空气和涡旋（在大气中旋转）的流入破坏了支持在否则受保护的环境中发展的动力学。 知识上的优点利用拉格朗日相干结构诊断风暴形成前的环境可能导致：（1）对波囊内外侧流跟随输送和交换的认识得到提高（2）对热带低气压向热带风暴转变的描述得到改进，包括对涡核剪切遮挡引起的运动学保护的诊断（3）扩展运动学分析以研究拉格朗日边界的垂直对准和对准或不对准对气旋生成的后果（风暴旋转）（4）通过将这些方法应用于集合预报来解决气旋生成的可预报性更广泛的影响对气流跟随作用的更全面的理解（拉格朗日）边界和涡核可能有助于改进风暴旋转的预报，具有更长的提前时间和更低的误报率。

This research builds on the "marsupial paradigm" to examine which pre-genesis disturbances eventually become tropical storms and hurricanes. A favorable environment most typically exists within African Easterly Wave (AEW) critical layer flows as an essential precursor environment for the dynamics (wind) and thermodynamics (heat and moisture) to support development. Though a protected kinematic environment is necessary for development, typically less than 20% of these waves actually produce hurricanes. Classic methods to evaluate the near storm environment use an Eulerian framework in which the storm is studied as it flows through a fixed domain. The proposed research seeks to study these flows through the use of Lagrangian Coherent Structure (LCS) analysis in which the diagnostic tools follow the air flowing into the developing pre-storm environment. Influx of moisture, dry air and vorticity (spin in the atmosphere) across closed streamlines of the steady flow disrupt the dynamics that support development in an otherwise protected environment. Intellectual MeritThe use of Lagrangian Coherent Structures in diagnosing the pre-genesis storm environment may lead to: (1) An improved understanding of the lateral flow-following transport and exchange of air masses interior and exterior to the wave pouch(2) An improved description of transitions from tropical depression to tropical storm including diagnosis of the kinematic protection due to the shear-sheltering of the vortex core(3) Extending the kinematic analysis to study vertical alignment of Lagrangian boundaries and consequences of alignment or misalignment for cyclogenesis (storm spin-up)(4) Addressing predictability of cyclogenesis by applying these methods to ensemble forecastsBroader ImpactsA more complete understanding of the role of flow-following (Lagrangian) boundaries and vortex cores may aid in improved forecasting of storm spin-up with greater lead-time and lower false alarm rates.