RAPID: Dual-Doppler Analysis of the Boundary Layer in Category-4 Hurricane Laura

飓风劳拉于2020年8月在路易斯安那州西南部登陆，是一场高端4级风暴。这次登陆为对袭击美国的最强风暴之一进行科学测量提供了一个独特的机会。两台移动多普勒雷达捕捉到了飓风低空风的精细细节，包括眼壁。该奖项是为了分析与飓风最低水平（即飓风边界层）有关的科学问题的雷达数据。这些数据与飓风预报界特别相关，因为对精确数值模拟很重要的特性测量很难进行。因此，这些数据可能对预测未来的飓风登陆有重要意义，这对公共安全和经济都很重要。研究小组计划分析在飓风劳拉眼壁收集的双多普勒数据，以提高对强飓风中飓风边界层结构的理解。在劳拉的内带和眼壁连续收集了多个小时的双多普勒数据，这是一个独特的主要飓风登陆或接近峰值强度的数据集。研究人员将推导出非常接近地面（距离地面100米）的三维风结构，以及湍流动能（TKE）、动量通量和动量交换（阻力）系数（Cd）的时间函数。利用这些数据需要解决的主要问题包括：1)飓风边界层滚动特征和相关的TKE、通量和Cd如何随背景风速和飓风位置的变化而变化；2)飓风边界层结构如何影响测量到的阵风？该奖项反映了美国国家科学基金会的法定使命，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。

Hurricane Laura made landfall in southwestern Louisiana in August 2020 as a high-end Category 4 storm. The landfall represented a unique opportunity to make scientific measurements of one of the strongest storms to hit the United States. Two Doppler on Wheels mobile radars captured fine-scale details of the low-level winds of the hurricane, including the eyewall. This award is for analysis of the radar data in relation to scientific questions about the lowest levels of a hurricane, known as the hurricane boundary layer. This data has particular relevance to the hurricane forecasting community, as measurements of properties that are important for accurate numerical modeling are difficult to conduct. Thus, the data may have significant relevance to forecasting of future hurricane landfalls, which is important for public safety and the economy.The research team plans to analyze dual-Doppler data collected in the eyewall of Hurricane Laura to improve understanding of hurricane boundary layer structure in an intense hurricane. Multiple hours of continuous dual-Doppler data were collected in the inner bands and eyewall of Laura, which is a unique dataset for major hurricane landfalls at or near peak intensity. The researchers will derive 3D wind structure very near the surface (100m above ground level) as a function of time, along with Turbulent Kinetic Energy (TKE), Momentum Flux, and the Momentum Exchange (Drag) Coefficient (Cd). The main questions to be addressed using these data include: 1) How do hurricane boundary layer roll characteristics and associated TKE, fluxes, and Cd vary as a function of background wind speed and location in the hurricane, and 2) How do hurricane boundary layer structures affect measured wind gusts?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.