An Observational and Modeling Study of Derecho-producing Convective Systems

了解每年造成大量人员伤亡和重大财产损失的大范围强对流风暴(DERECO)的形成和维持机制，仍然是一个重要的研究重点。这些机制已经通过对强的、以线为导向的对流(狂风线)的理想化模拟来检验，其中产生反回声的对流系统是其中的一个子集。这些过去的研究强调了环境风切变在控制斜风线的强度和寿命方面的重要性。虽然最近描述观测到的DERECHO环境的研究表明，低水平切变并不像一些数值模拟所表明的那样是一个主要因素，但缺乏描述DERECHO环境的详细观测基线阻碍了将这些想法与观测进行比较。为了解决这些问题，已经确定了三个主要目标：1)从德回波收集和分析大量的近距离探空，并确定风切变和与这些事件有关的其他参数的分布；2)制作一套理想化的数值模拟，以检查线定向对流对本项目观测部分确定的一系列环境的敏感性；3)检查在数值模拟实验中维持强上升气流和强近地面风的力量。这项研究将对DERECHO环境中观测到的风和热力学廓线进行详细的分类，并将增加我们对这些类型天气系统中以线为导向的对流和强地面风的发展和维持的物理机制的了解。结果可能会导致对这些破坏性风暴的更好预测。

Understanding the mechanisms responsible for the development and maintenance of widespread severe convective windstorms (derechos), that are responsible for numerous casualties and significant property damage each year, remains an important research focus. These mechanisms have been examined with idealized simulations of strong, line-oriented convection (squall lines) of which derecho-producing convective systems are a subset. These past studies emphasize the importance of environmental wind shear in controlling the strength and longevity of squall lines. While recent studies describing observed derecho environments suggest that low-level shear is not as dominant a factor as some numerical simulations have suggested, the lack of a detailed observational baseline describing derecho environments has hindered the comparison of these ideas to observations. To address these issues three main objectives have been defined: 1) collect and analyze a large set of proximity soundings from derechos and determine the distribution of wind shear and other parameters associated with these events; 2) produce a set of idealized numerical simulations to examine the sensitivity of line-oriented convection to the range of environments identified in the observational portion of this project; 3) examine the forces responsible for maintaining the strong updrafts and the strong near-surface winds within the numerical modeling experiments. This study will produce a detailed classification of the observed wind and thermodynamics profiles in derecho environments and will increase our knowledge of the physical mechanisms responsible for the development and maintenance of the line-oriented convection and the strong surface winds within these types of weather systems. Results potentially will lead to better forecasts of these destructive wind storms.