Collaborative Research: Understanding Tropical Cyclone Energetics and Intensification in Environmental Vertical Wind Shear

环境垂直风切变是影响热带气旋发展的主要因素之一。风切变也促进了干空气侵入TC核心区，降低了对流上升气流的浮力。然而，TC在轻至中等剪切条件下确实发展或甚至经历快速强化（RI）。如何准确预报热带气旋增强的时间和速率，特别是RI，是热带气旋数值预报的一个重大挑战。因此，了解克服切变引起的对TC增强的负面影响的物理过程对于TC强度预报的潜在改进是重要的。迄今为止的研究表明，几个过程，如减少通风和边界层恢复，由于表面焓通量的增强，可以克服由切变造成的负面影响，导致TC涡的加强。然而，在TC的能量和动力学路径与这些过程相关的TC强化的细节仍然知之甚少。该项目的总体目标是推进对剪切环境中TC强度在生成阶段之后变化的机制的理解。研究发现，在不同切变和热力环境下，影响热带气旋强度变化的主要物理过程，将为热带气旋强度变化的业务预报提供指导。这个项目的目的是提供新的见解，了解在使用理想化的飓风的切变环境中，控制热带气旋增强的关键热力学变化及其动力学响应天气研究和预报灵敏度数值试验和天气研究和预报Enhanced数据同化系统产生的数据，该系统具有在数值系统中同化具有不同时间和空间分辨率的风暴相关观测的能力。对HEDAS数据集和HWRF理想化模拟进行了综合分析。研究活动包括：（a）在湿静能框架内分析生成后阶段的热带气旋能量学;（B）利用一种新的诊断工具探索热带气旋能量学和涡旋旋转动力学之间的联系，这种诊断工具可以更好地理解在不平衡框架内各种动力和热力强迫驱动的热带气旋强化;以及（c）关于减少中低层通风和边界通风的作用的关键问题的调查-在剪切环境中使用包裹轨迹分析进行TC强化的层恢复。该奖项反映了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。

Environmental vertical wind shear has long been recognized as a major inhibiting factor for tropical cyclone (TC) intensification since it acts to tilt the vortex. The wind shear also facilitates the dry-air intrusion into the TC core region to reduce the buoyancy of convective updrafts. Yet, TCs do develop or even undergo rapid intensification (RI) in light to moderate shear conditions. An accurate prediction of both timing and rate of TC intensification in such conditions, in particular RI, poses a great challenge in numerical forecasts of TCs. Understanding the physical processes that overcome the shear induced negative effects on TC intensification is, thus, important for the potential improvement of TC intensity forecasts. Research to date showed that several processes, such as the reduction in ventilation and boundary-layer recovery due to the enhancement of surface enthalpy fluxes, could overcome the negative impacts imposed by the shear, leading to the intensification of a TC vortex. However, details in TC energetics and dynamical route to TC intensification associated with these processes remain poorly understood. The overall goal of this project is to advance the understanding of mechanisms underlying the TC intensity change after the genesis stage in a sheared environment. The identified key physical processes that differentiate the TC intensification rates in different shear and thermodynamic environments will provide useful guidance for operational forecast of TC intensity change including both RI and slow intensification.To achieve the research objectives, this project aims to provide new insights into the key thermodynamic changes and their dynamic responses that govern TC intensification in a sheared environment using idealized Hurricane Weather Research and Forecast (HWRF) sensitivity numerical experiments and the data generated by the HWRF Ensemble Data Assimilation System (HEDAS) that possesses the ability to assimilate storm-relative observations with different time and spatial resolutions in the numerical system. Comprehensive analyses on the HEDAS dataset and HWRF idealized simulations are carried out. Research activities include (a) analyses of TC energetics during post-genesis stages within the moist static energy (MSE) framework; (b) Exploration of the linkage between TC energetics and vortex spin-up dynamics using a novel diagnostic tool that can yield an improved understanding of the TC intensification driven by various dynamic and thermodynamic forcing in an unbalance framework; and (c) Investigation of key issues regarding the role of the reduction of mid- and low-level ventilation and boundary-layer recovery in TC intensification in a sheared environment using parcel trajectory analyses.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.