Improved understanding of bow echo evolution and long-lasting significantly severe thunderstorm winds

有组织的雷暴线，通常被称为飑线或中尺度对流系统，可以产生大面积的破坏性风。有两种现象与大风特别相关：弓形回波是嵌入在较大的线路中的一小段，包含较大的风，并且似乎在线路的其余部分之前“弓形”，而脱回声是非常长寿命的线路，在很大范围内产生明显的风。本研究将使用精细分辨率数值模拟来研究导致弓形回波和去回波的过程。这些事件的高影响性质意味着更好的理解和更好的预测将在公共安全和经济利益方面带来巨大的红利。此外，不同层次的学生将参与该项目，从而培养下一代科学家。该奖项的目标是提高对中尺度对流系统（mcs）形态演变的理解，重点是弓形回波和与其中一些相关的严重持久风的形成（称为derecho事件）。该计划将利用天气研究及预报（WRF）和第一云模式（cm2）数值模式，研究MCSs的各个方面。具体而言，该项目将：•检查过程对mcs高档增长的作用，特别是冷池前缘温度梯度的强度，冷池前缘重力波和直接升力的贡献，以及它们对对流的敏感性，允许模型（CAM）网格间距的模拟。•检查导致弓形回波形成的过程，重点关注流入的方向、线与已有单元的合并、边界的存在以及它们对CAM网格间距的敏感性。•提高对MCSs中导致长时间显著强风的过程的理解，包括环境中干燥空气的垂直位置等特征的作用，在某些情况下导致强烈中尺度涡旋形成的因素，以及这些涡旋是否对形成特别强烈、长时间的风带是必要的。•通过伪全球变暖方法研究气候变化对derecho事件的影响。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。

Organized lines of thunderstorms, often known as squall lines or mesoscale convective systems, can produce large swaths of damaging winds. Two phenomena are particularly associated with high winds: bow echoes which are small segments embedded in a larger line that contain higher winds and seem to “bow” out ahead of the rest of the line, and derechos which are very long-lived lines which produce significant winds across a large area. This study will use fine resolution numerical modeling to investigate the processes that lead to bow echos and derechos. The high-impact nature of these events means that better understanding and the likelihood for better forecasting will have large dividends in terms of public safety and economic benefits. Additionally, students at various levels would be involved in the project, thereby training the next generation of scientists.The goal of this award is to improve understanding of the morphological evolution of mesoscale convective systems (MCSs), with an emphasis on bow echoes and the formation of significantly severe long-lasting wind associated with some of them (known as derecho events). The project will make use of the Weather Research and Forecasting (WRF) and Cloud Model 1 (CM1) numerical models to study various aspects of MCSs. In particular, the project will:• Examine the role of processes contributing to upscale growth in MCSs, particularly the strength of the temperature gradient at the leading edge of the cold pool, and contribution of gravity waves and direct lift at the leading edge of the cold pool, and their sensitivity to convection allowing model (CAM) grid spacing in simulations. • Examine the processes leading to bow echo formation, with emphasis on orientation of inflow, merger of lines with pre-existing cells, and presence of a boundary, and their sensitivity to CAM grid spacing.• Improve understanding of processes leading to long-lived significantly severe winds in MCSs, including the roles of features like the vertical position of dry air in the ambient environment, factors leading to intense mesoscale vortex formation in some cases, and whether such vortices are necessary for particularly strong, long-lived swaths of wind to form.• Study the impact of climate change on derecho events explored through the pseudo-global warming approach.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.