Studies of the Internal Structure and Dynamics of Convective Weather Systems

首席调查员将研究中尺度对流系统对流区的内部结构和动力学。主要目的是确定为什么潮湿对流在某些情况下表现为离散的雷暴，而在其他情况下表现为固体中尺度条带(平板)倾覆。具体目标包括：1)构建离散雷暴事件和板条事件的特征流入环境，2)确定伴随胞状对流和板状对流的动力和热力学条件的局部(在对流区域内)差异，以及3)确定对流(板状对流与板状对流)的差异如何影响对流系统的中尺度动力学和结构特性。研究方法由三部分组成：1)为观测到的以蜂窝状对流系统为主的情况和表现为固体-板块翻转的系统建立复合环境，2)在复合环境上进行数值试验，以确定模式是否能够产生两种类型的组织模式，3)以第(1)项和第(2)项的结果为指导，在理想化(解析指定)初始条件下进行数值敏感性试验。这些研究的结果将有助于a)确定建立对流组织模式的因素以及湿绝对不稳定层的深度和强度，b)阐明这些因素如何影响中尺度对流系统的整体结构和演变。这些结果还可能带来实际的好处，例如提高区分各种类型的大范围环境中将发生的恶劣天气的能力。从预报的角度来看，区分对流组织的可能模式是极其重要的，因为正是这些差异往往决定了是否会发生恶劣天气，如果是的话，它是以个别的、可能是旋转的风暴为特征，还是以与板条对流有关的强直线风为特征。

The Principal Investigator will investigate the internal structure and dynamics of the convective region of mesoscale convective systems. The main goal is to determine why moist convection appears as discrete thunderstorms in some situations and as solid mesoscale swaths (slabs) of overturning in others. Specific objectives include 1) constructing characteristic inflow environments for discrete-thunderstorm events and for slab events, 2) determining the local (within the convective region) differences in the dynamic and thermodynamic conditions that accompany cellular vs. slab convection, and 3) determining how differences in the convection (slab vs. cellular) affect the mesoscale dynamics and structural properties of the convective system.The research methodology is composed of three parts: 1) construction of a composite environment for observed cases of predominantly cellular convective systems and for systems exhibiting solid-slab overturning, 2) numerical experiments on the composite environments to determine whether or not the model is able to generate the two types of organizational modes, and 3) numerical sensitivity experiments on idealized (analytically specified) initial conditions using the results of items (1) and (2) as a guide.It is expected that the knowledge gained from these investigations will a) help to identify the factors that establish the organizational mode of the convection and the depth and strength of moist absolutely unstable layers, and b) elucidate how those factors affect the overall structure and evolution of mesoscale convective systems. The results may also provide practical benefits, such as improvements in the ability to discriminate among the types of severe weather that will occur for various types of large-scale environments. Differentiating among the possible modes of convective organization is extremely important from a forecasting perspective since it is these differences that often determine whether or not severe weather will occur and, if so, whether it will be characterized by individual, possibly rotating, storms or by strong straight line winds associated with slab convection.