Numerical Investigation of Convective Initiation and Maintenance

首席调查员将利用数值模拟扩展先前关于大气对流的启动、结构和行为的研究。这项研究的一部分致力于研究斜线风暴，另一部分则侧重于与海风锋面(SBF)和水平对流卷(HCRS)相关的对流。两者之间有相当大的和有益的协同作用，特别是在对流启动的研究方面。在广场线模拟中，经常在模式风暴上游的流入中看到的小扰动可以起到对流触发作用，加速新的单体形成，甚至保持有组织的对流活动。这些扰动似乎是对风暴运动和环流的响应，并位于似乎受到风暴本身预条件的环境的一部分，使这种启动更有利于发生。在SBF的情况下，边界层滚动提供了(现在独立的)上游扰动。SBF和HCR环流可以结合在一起产生深对流，而这两种现象在孤立的情况下都不能做到这一点。锋线和SBF/HCR现象都提供了影响对流启动的三个因素的有趣的相互作用：运动控制、水汽控制和动力强迫。运动学控制包括波浪、旋涡等对对流启动或抑制的直接影响；HCRS就是一个例子。前述的预适应是一种湿度控制：环境对风暴内部和周围的潜热和降温做出反应，往往会通过在风暴的上游环境中创造一个凉爽和潮湿的空气舌来进行调整，触发因素往往就是在这个舌头上形成的。这些触发因素可能起源于由对流本身激发并通过上游环境的瞬变重力波；这将代表动力强迫。这项研究中使用的工具之一包括一个伴随云模型，该模型将用于敏感性分析和动态跟踪。伴随项在对流启动研究等情况下会有很大的用处，在这种情况下，可能有不止一个过程或因素是活跃的，而且还不清楚哪一个是关键的或原始的。这项研究的成功完成将有助于更好地理解对流降水系统的启动。

The Principal Investigator will extend prior research concerning the initiation, structure and behavior of atmospheric convection utilizing numerical simulations. Part of the research is dedicated to the study of squall line storms and part focuses on convection associated with sea breeze fronts (SBFs) and horizontal convective rolls (HCRs). There is a considerable and profitable synergy between the two, particularly with regard to the study of convective initiation.In squall line simulations, the small perturbations that are often seen in the inflow just upstream of the model storms can act as convective triggers, expediting new cell formation and even keeping the organized convection active. These perturbations appear to be generated in response to storm motions and circulations and reside in a portion of the environment that appears to be preconditioned by the storm itself, making it more favorable for this initiation to occur. In the case of the SBF, the boundary layer rolls provide the (now independent) upstream perturbation. The SBF and HCR circulations can combine to create deep convection in situations where neither phenomenon could do so in isolation.Both the squall line and the SBF/HCR phenomena provide an interesting interplay of the three factors that influence convective initiation: kinematic controls, moisture controls and dynamical forcing. Kinematic controls include the direct effect of waves, vortices, etc., on convective initiation or inhibition; the HCRs represent one example. The aforementioned preconditioning is a moisture control: the environment, responding to latent heating and cooling in and around the storm, tends to adjust by creating a cooled and moistened tongue of air in the storm's immediate upstream environment, and the triggers tend to form in this tongue. These triggers may have their genesis in transient gravity waves excited by the convection itself and passing through the upstream environment; this would represent a dynamical forcing. One of the tools to be utilized in this research includes an adjoint cloud model, which will be used for sensitivity analysis and dynamical tracking. The adjoint will be of significant use in situations such as the convective initiation study, in which more than one process or factor may be active and it isn't clear which is the pivotal or primordial one. Successful completion of this research will lead to better understanding of the initiation of convective precipitating systems.