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，以检查哪些发生前的扰动最终成为热带风暴和飓风。最典型的有利环境存在于非洲东风（AEW）临界层气流中，作为支持发展的动力学（风）和热力学（热和湿）的基本前驱环境。虽然受保护的运动环境对发展是必要的，但通常只有不到20%的海浪真正产生飓风。评估近风暴环境的经典方法使用欧拉框架，在欧拉框架中，风暴在流过固定区域时进行研究。拟议的研究试图通过使用拉格朗日相干结构（LCS）分析来研究这些流动，其中诊断工具跟踪流入发展中的风暴前环境的空气。湿气、干燥空气和涡旋（大气中的旋转）穿过稳定气流的封闭流线，破坏了在其他受保护的环境中支持发展的动力学。利用拉格朗日相干结构诊断发生前的风暴环境可能导致：(1)提高了对波袋内外气团的横向流动运输和交换的理解(2)改进了从热带低气压到热带风暴转变的描述，包括由于涡旋核心的剪切庇护而产生的运动学保护的诊断(3)将运动学分析扩展到研究拉格朗日边界的垂直对齐以及对齐或不对齐对气旋形成（风暴自旋上升）的后果(4)定位更广泛的影响更全面地了解流动跟随（拉格朗日）边界和涡旋核的作用，可能有助于提高预报风暴自旋上升的提前时间，降低误报率。

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.