Modeling Studies of Transitions from Slow to Fast Tropical Cyclone Intensification

热带气旋从慢速强度到快速强度转变的模拟研究

• 批准号: 2208205
• 负责人: David Schecter
• 金额: $ 39.99万
• 依托单位: NorthWest Research Associates, Incorporated
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2208205&HistoricalAwards=false
• 关键词: Modeling; Studies; Transitions; Slow; Fast

This research project is part of a broader effort to advance current understanding of how underdeveloped tropical cyclones intensify into potentially devastating hurricanes. Computer modeling studies will be conducted to address deficiencies in our knowledge of the nature and effectiveness of the intensification process that operates when there exists markedly asymmetric convection linked to substantial misalignment of the mid-level and low-level cyclonic circulations (tilt). Changes to the asymmetric state that are required for a fast intensification mechanism to supersede a slow mechanism, and the time scale for such changes to occur under a variety of environmental conditions will be elucidated. Knowledge gained from this project will assist complementary efforts to improve the accuracy of operational intensification forecasts that determine the preparations needed to adequately mitigate damage to coastal or island communities that lie in the predicted path of a tropical cyclone. In addition to offering new insights relevant to forecasting, this project will support student internships that will contribute to the development of the next generation of atmospheric scientists.The research strategy will entail a combination of reduced and full-physics modeling studies. The reduced modeling studies will add parameterized diabatic forcing to the dry primitive equations primarily to represent the heating associated with convection concentrated downtilt of the lower tropospheric vortex center. A variety of intensification mechanisms are expected to exist over the expansive multidimensional parameter space of the diabatic forcing, the state of the vortex, and the environmental vertical wind shear. The spectrum of possibilities ranges from very slow asymmetric modes of spinup to a fast mode associated with core reformation. The domain of applicability for each distinct intensification mechanism will be determined through extensive numerical experiments. Theoretical formulas will be sought for the hypersurfaces that separate regions of parameter space in which different intensification mechanisms operate. The full-physics simulations will be used to elucidate the moist thermo-fluid dynamics governing the convection that drives each intensification mechanism, and to elucidate the processes that lead a tropical cyclone to transition from slow to fast spinup. The sea surface temperature and vertical wind shear will be varied to uncover an assortment of transition-types and the environments in which they occur. Many of the transitions are expected to transpire through contraction or shear-relative reorientation of the tilt vector that characterizes the misalignment of the tropical cyclone. Thus, to better understand what controls the timing of a transition to fast spinup, a sizeable part of this project will involve analyzing how diabatic processes regulate the decay and precession rates of the tilts of the simulated tropical cyclones.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.

这个研究项目是一个更广泛的努力，以促进目前的了解如何欠发达的热带气旋加强成为潜在的破坏性飓风的一部分。将进行计算机模拟研究，以解决我们对强化过程的性质和有效性的认识不足的问题，强化过程是在存在明显不对称对流的情况下进行的，这种对流与中层和低层气旋环流（倾斜）的实质性错位有关。将阐明快速强化机制取代缓慢机制所需的非对称状态的变化，以及在各种环境条件下发生这种变化的时间尺度。从这个项目中获得的知识将有助于补充努力，以提高业务强化预报的准确性，确定为充分减轻热带气旋预测路径上的沿海或岛屿社区所受损害所需的准备工作。除了提供与预测相关的新见解外，该项目还将支持学生实习，这将有助于下一代大气科学家的发展。研究战略将需要将简化和全物理建模研究相结合。简化的模拟研究将把参数化的非绝热强迫加入到干燥的原始方程中，主要是为了表示与对流层下部涡旋中心的对流集中下倾有关的加热。在非绝热强迫、涡旋状态和环境垂直风切变的多维参数空间中，预计存在各种各样的强化机制。光谱的可能性范围从非常缓慢的非对称模式的自旋到快速模式与核心改革。每个不同的强化机制的适用范围将通过广泛的数值试验来确定。将寻求理论公式的超曲面，分离区域的参数空间中，不同的强化机制的运作。全物理模拟将用于阐明驱动每种增强机制的对流的湿热流体动力学，并阐明导致热带气旋从缓慢旋转转变为快速旋转的过程。海洋表面温度和垂直风切变将被改变，以揭示各种各样的过渡类型和它们发生的环境。许多转变预计将通过收缩或倾斜矢量的剪切相对重新定向而发生，这是热带气旋错位的特征。因此，为了更好地理解是什么控制着向快速旋转转变的时间，这个项目的很大一部分将涉及分析非绝热过程如何调节模拟热带气旋倾斜的衰减和岁差率。这个奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Intensification Rates of Tropical Cyclone–Like Vortices in a Model with Downtilt Diabatic Forcing and Oceanic Surface Drag

• DOI: 10.1175/jas-d-22-0188.1
• 发表时间: 2023-07
• 期刊: Journal of the Atmospheric Sciences
• 影响因子: 3.1
• 作者: D. Schecter