An Observational and Modeling Study of Derecho-producing Convective Systems

广泛的强对流风暴（derechos）每年造成大量人员伤亡和重大财产损失，了解其发展和维持的机制仍然是一个重要的研究重点。这些机制已经通过强的、面向线的对流（飑线）的理想化模拟进行了检验，其中产生脱回波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飑线强度和寿命方面的重要性。虽然最近描述观测到的脱回波环境的研究表明，低层切变并不像一些数值模拟所表明的那样是一个主要因素，但缺乏描述脱回波环境的详细观测基线阻碍了这些观点与观测结果的比较。为了解决这些问题，我们确定了三个主要目标：1)收集和分析大量来自回波的近距离探测数据，确定风切变的分布以及与这些事件相关的其他参数；2)建立一套理想化的数值模拟，以检验线向对流对该项目观测部分确定的环境范围的敏感性；3)在数值模拟实验中考察了维持强上升气流和强近地面风的力量。这项研究将产生在脱回波环境中观测到的风和热力学剖面的详细分类，并将增加我们对这些类型天气系统中线状对流和强地表风的发展和维持的物理机制的认识。研究结果可能有助于更好地预测这些破坏性风暴。

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.