Numerical Simulations of Derecho-producing Convective Systems

了解大范围强对流风暴（derechos）发展和维持的环境和机制仍然是一个重要的研究重点。这些环境和机制已经通过强的、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低层风切变在控制飑线强度和寿命方面的重要性。然而，最近描述观测到的脱回波环境的研究表明，低层剪切并不是主要因素。为了解决这些问题，已经确定了两个主要目标：1)在与脱回波相关的观测环境范围内，产生一套相当全面的水平非均匀数值模拟；2)产生一套类似的水平均匀云模式模拟。本研究将使用在derecho环境中观测到的风和热力学剖面的详细分类作为数值模拟的基线。这一建议的智力价值在于，观测到的derecho环境和理想化模式模拟的结果之间的差异将在很大程度上得到调和，并且我们对这些类型天气系统中线向对流和强地面风的发展和维持的物理机制的了解将增加。更广泛的影响是改善对流风暴的预报，从而提高公共安全，并为商业带来经济效益。

Understanding the environments and mechanisms responsible for the development and maintenance of widespread severe convective windstorms (derechos) remains an important research focus. These environments and 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 low-level wind shear in controlling the strength and longevity of squall lines. However, recent studies describing observed derecho environments have suggested that low-level shear is not a dominant factor. To address these issues, two main objectives have been defined: 1) produce a reasonably comprehensive set of horizontally non-homogeneous numerical simulations within the range of observed environments associated with derechos, and 2) produce an analogous set of horizontally homogeneous cloud-model simulations. This study will use a detailed classification of the observed wind and thermodynamics profiles in derecho environments as a baseline for the numerical simulations. The intellectual merit of this proposal is that the disparity between the results derived from observed derecho environments and those derived from idealized model simulations largely will be reconciled, and 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 will be increased. The broader impacts are the improved forecasts of convective windstorms, resulting in enhanced public safety and economic benefits to commerce.