Diagnosis of the Sensitivity of Type B Cyclones to the Structure and Evolution of Their Upper-Tropospheric Precursors

中纬度地面气旋，即地面天气图上常见的“低压系统”，是降水、强风和温度快速变化的重要组织者和制造者。 这些表面气旋（气旋生成）的发展和随后的加强通常是在地面以上9-13公里处的扰动发展之前（即，对流层上部和平流层下部）。对气旋生成的研究揭示了两个阶段：第一，对流层上层锋的发展以及平流层空气进入对流层上层和中层的相关挤出，与气旋生成中的风切变有关。 第二，在气旋生成中切变转变为曲率的发展时期。 结果表明，平流层空气向对流层上层的挤压过程以及这两个步骤的转换不仅对配置上层低压槽以进行后续的气旋生成很重要，而且对形成后续的气旋增强率也很重要。目前还不清楚这些过程如何协同相互作用或这些过程中的每一个假设在气旋发生的个人重要性。这个项目将探讨模拟的对流层上部气旋前兆的初始条件的微小变化如何影响地面气旋的演变。这个拟议项目的结果将提供洞察力的时间和位置的关键过程发生在对流层上部气旋发生之前，并可能提供洞察力的改进，以减少与这些天气事件的强度预测的不确定性。本项目所进行的基础研究与NSF促进科学进步的使命是一致的。拟议活动的更广泛影响包括培训研究生，组织和主办一次研讨会，探讨旋风及其生命周期的可预测性，和组织一次关于中期在2022年美国气象学会年会上，本研究提出了通过解决热带气旋的敏感性来研究中纬度气旋发生事件的动力学在模拟观测到的气旋生成事件的案例研究框架内，发展到对流层上部气旋生成前兆（UTCP）的演变。 该项目结合了两种成熟的诊断技术（即，准地转（QG）诊断和伴随导出的预报敏感性），以了解与中纬度气旋生成有关的一个突出问题：B型气旋生命周期对气旋上部对流层气旋生成前兆扰动的敏感性。诊断方法的独特组合允许以前未探索的研究，了解对流层上层，前气旋，正压和斜压增长过程中调制表面气旋生命周期的单独和相互作用。我们将使用一种新的实验方法，称为灵敏度扰动响应诊断（SPRD）程序。 SPRD采用伴随导出的灵敏度梯度个别情况下，构建最佳扰动，引起特定的，规定的响应在模拟的气旋生命周期的天气尺度QG和位涡（PV）反演诊断的扰动气旋演变进行。采用这种方法将导致对影响气旋发展的最佳初始扰动的结构和演变进行全面检查，该奖项反映了美国国家科学基金会的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查进行评估来支持的的搜索.

Mid-latitude surface cyclones, the familiar "low-pressure systems" seen on surface weather maps, are significant organizers and producers of precipitation, strong winds, and rapid changes in temperature. The development and subsequent intensification of these surface cyclones (cyclogenesis) is often preceded by the development of a disturbance 9-13 kilometers above the surface (i.e., the upper-troposphere and lower-stratosphere). Studies of cyclogenesis have revealed two stages: First, development of an upper-tropospheric front and associated extrusion of stratospheric air into the upper and mid-troposphere associated with wind shear in cyclogenesis. Second, a period of development during which shear is converted to curvature in cyclogenesis. It has been shown that processes of extrusion of stratospheric air into the upper-troposphere and the subsequent conversion of these two steps are not only important in configuring the upper-trough for subsequent cyclogenesis, but also in shaping the subsequent intensification rate of the cyclone. It is unclear how these processes synergistically interact or what individual importance each of these processes assumes in cyclogenesis. This project will explore how small changes to the initial conditions of simulated upper-tropospheric cyclone precursors impacts the evolution of the surface cyclone. The results of this proposed project will provide insight into the timing and location of critical processes occurring in the upper-troposphere prior to cyclogenesis and potentially offer insight into improvements in reducing the uncertainty associated with predictions of the intensity of these weather events. The fundamental research conducted in this project is consistent with NSF's mission of promoting the progress of science. The broader impacts of the proposed activity include the training of graduate students, the organization and hosting of a workshop to explore the predictability of cyclones and their lifecycles, and the organization of a session on mid-latitude lifecycles at the 2022 annual meeting of the American Meteorological Society.This study proposes to investigate the dynamics of midlatitude cyclogenesis events by addressing the sensitivity of extratropical cyclone development to the evolution of the upper tropospheric cyclogenetic precursor (UTCP) within the framework of case studies of simulated observed cyclogenesis events. The project combines two well-developed diagnostic techniques (i.e., quasi-geostrophic (QG) diagnostics and adjoint-derived forecast sensitivities) to understand an outstanding issue related to mid-latitude cyclogenesis: the sensitivity of the Type-B cyclone lifecycles to perturbations to the cyclones' upper-tropospheric cyclogenetic precursors. The unique combination of the diagnostic approaches allows for previously unexplored research into understanding the separate and interactive roles of upper-tropospheric, pre-cyclogenetic, barotropic and baroclinic growth processes in modulating surface cyclone lifecycles. We will use a novel experimental approach termed the sensitivity-perturbation-response-diagnosis (SPRD) procedure. SPRD employs adjoint-derived sensitivity gradients for individual cases to construct optimal perturbations that elicit particular, prescribed responses in the simulated cyclone life cycle for which synoptic-scale QG and potential vorticity (PV) inversion diagnostics of the perturbed cyclone evolutions are performed. Employment of this procedure will result in a comprehensive examination of the structure and evolution of optimal initial-time perturbations influencing the cyclone's development, as well as a test of the appropriateness of the simplifying assumptions in the adjoint model to each particular case.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.