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

成因前扰动中的拉格朗日流边界、输运和涡核

• 批准号: 1439283
• 负责人: Blake Rutherford
• 金额: $ 58.98万
• 依托单位: NorthWest Research Associates, Incorporated
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1439283&HistoricalAwards=false
• 关键词: Lagrangian; Flow; Boundaries; Transport; Vortex

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.

这项研究建立在“有袋动物范式”的基础上，研究哪些成因前的干扰最终会变成热带风暴和飓风。 有利的环境通常存在于非​​洲东风波 (AEW) 关键层流中，作为动力学（风）和热力学（热量和湿度）支持发展的重要前体环境。 尽管受保护的运动环境对于发展来说是必要的，但通常只有不到 20% 的波浪实际上会产生飓风。 评估近风暴环境的经典方法使用欧拉框架，在该框架中研究风暴流经固定域时的情况。 拟议的研究旨在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正在发展的风暴前环境的空气。 湿气、干燥空气和涡流（在大气中旋转）穿过稳定流的封闭流线的流入破坏了在受保护的环境中支持发展的动力。 智力优点使用拉格朗日相干结构来诊断风暴前环境可能会导致：（1）更好地理解波袋内部和外部气团的横向流动输送和交换（2）改进从热带低气压到热带风暴的过渡描述，包括诊断由于涡核的剪切遮挡而产生的运动保护（3）扩展 运动学分析，研究拉格朗日边界的垂直对齐以及对齐或未对齐对气旋发生（风暴自旋）的后果(4) 通过将这些方法应用于集合预报来解决气旋发生的可预测性更广泛的影响更全面地了解流动（拉格朗日）边界和涡核的作用可能有助于改进对风暴自转的预测，提前时间更长，成本更低 误报率。