Observational and Numerical Modeling Study of Downburst Generation Using Dual-Polarization Radar

这个项目是研究一种被称为下击暴流的危险天气现象。下击暴流是一种快速下降的空气柱，可能会造成强烈的破坏性风，对航空，基础设施，牲畜和人类生命构成威胁。气象学家依靠天气雷达数据来探测正在发展的下击暴流，但由于它们相对局部化，而且发展迅速，因此通常很难提前发出警告。然而，雷达技术的最新进展现在允许更好地了解导致下击暴流的因素，但尚未进行全面的研究来检查这些特征。通过更好地了解下击暴流的原因以及这些因素在现有雷达数据中的表现，预报员将能够在它们到达地面之前更好地预测它们的发生和强度，从而提供更早的警告，减少误报，并为人们提供更多的时间来安全地寻找避难所。此外，随着计算机在决定何时发布恶劣天气警报方面发挥越来越大的作用，从这项研究中获得的见解将有助于确定天气模型模拟下击暴流的可靠性，并为未来的自动下击暴流检测提供基础。该项目涉及指导一名研究生成为下一代大气科学家。本研究旨在利用观测和数值模拟的下击暴流在一个互补的方式来了解负浮力的驱动下击暴流和它们的表现在观测到的双极化雷达变量的来源之间的关系。一种新的细胞跟踪算法将被用来全面调查下击暴流的偏振特性及其在各种热力学环境和地理区域的变化。此外，耦合到前向偏振雷达操作员的具有光谱箱微物理学的一维模型将用于模拟下击暴流，并定量检查环境、负浮力源（即，降水负荷和非绝热冷却），以及由此产生的下击暴流强度与模拟的偏振变量的演变和空间分布。根据前两个部分的研究结果，本研究的第三部分将评估现有对流解析模型与体微物理方案真实模拟下击暴流的能力，并确定限制其实用性的任何缺陷。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

This project is to study a hazard weather phenomenon known as downbursts. The Downbursts are rapidly descending columns of air that can cause strong, damaging winds that pose a threat to aviation, infrastructure, livestock, and human life. Meteorologists rely on weather radar data to detect developing downbursts, but because they are relatively localized and can develop quickly, it is often difficult to issue warnings for them in advance. However, recent advancements in radar technology now permit improved insight into the factors that lead to downbursts, but a comprehensive study examining such signatures has yet to be performed. By better understanding the causes of downbursts and what these factors look like in their existing radar data, forecasters will be able to better anticipate their occurrence and intensity before they reach the ground, and thus provide earlier warnings with fewer false alarms and more time for people to safely seek shelter. In addition, as computers play an increasingly large role in deciding when to issue severe weather warnings, the insights gained from this study will help determine how reliably weather models simulate downbursts and provide the basis for future automated downburst detection. The project involves mentoring a graduate student to be the next generation of atmospheric scientists. This study seeks to use both observations and numerical simulations of downbursts in a complementary manner to understand the relation between the sources of negative buoyancy that drive downbursts and their manifestation in observed dual-polarization radar variables. A novel cell-tracking algorithm will be used to comprehensively survey the polarimetric characteristics of downbursts and their variability across a variety of thermodynamic environments and geographic regions. Additionally, a one-dimensional model with spectral bin microphysics that is coupled to a forward polarimetric radar operator will then be used to simulate downbursts and quantitatively examine the association between the environment, sources of negative buoyancy (i.e., precipitation loading and diabatic cooling), and the resultant downburst intensity with the evolution and spatial distribution of the simulated polarimetric variables. Informed by the findings of the first two components, the third part of this study will evaluate the ability for existing convection-resolving models with bulk microphysics schemes to realistically simulate downbursts and identify any deficiencies limiting their usefulness.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.