A Theoretical and Observational Study of Midlatitude Mesoscale Convective Vortices (MCVs) in Vertical Shear

中尺度对流涡旋(MCV)由于其寿命长和组织对流的能力，一直是寻求改善暖季大范围强降水事件预报的研究重点。尽管在过去十年中，在确定有利于MCV产生的条件以及将MCV的加强与其附近的对流再生联系起来方面取得了进展，但支配MCV生命周期的动态过程仍然不是很清楚。为了更好地预测与MCV相关的潜在洪灾事件，需要基本了解MCV是如何形成的，以及是什么允许它们在不利的环境流中保持一致性。首席调查员(PI)将在弓回声和MCV实验(BAMEX)的支持下解决这两个问题。观察表明，MCV的形成和寿命关键取决于MCV与环境垂直切变的相互作用。为了进一步了解这种相互作用，PI将在PI和Co-PI之前的NSF研究的基础上进行一项理论、数值和观测相结合的研究。理论研究将从考察理想的MCV的准地转“自由”排列开始。这为关键的理论分析奠定了基础，以确定不可逆转地剪切给定的MCV所需的临界剪切。临界切变的知识被认为是区分那些能再生对流的MCV和不能再生对流的MCV的核心。将系统地研究由涡旋对环境切变的阻力所触发的新对流的影响，目的是确定对流对MCV强度的反馈。理论工作将利用机载多普勒雷达和来自BAMEX的MCV探测数据进行观测试验。特别是，将使用以前开发的诊断工具记录与MCV和附近对流有关的涡度演变，以研究飓风核心的动力学和热带气旋的成因。目前，还没有详细的观测数据集详细描述MCV的径向涡度结构、MCV倾角和强度的演变以及与再生对流相关的涡度发展，所有这些都是BAMEX研究目标的基本要素。这项研究的成功完成可能为预报员提供必要的知识，以延长对暖季对流风暴的预测时间。

Because of their longevity and ability to organize convection, mesoscale convective vortices (MCVs) have been the focus of studies seeking to improve the prediction of widespread, heavy precipitation events during the warm season. Although progress has been made in the past decade toward identifying conditions favorable for MCV generation, and in linking the strengthening of MCVs to convective regeneration in their vicinity, dynamical processes governing the MCV lifecycle are still not well understood. To better predict potential flooding events in association with MCVs requires a basic understanding of how MCVs form, and what permits them to maintain their coherence in adverse environmental flows. The Principal Investigator (PI) will address both questions under the aegis of the Bow Echo and MCV Experiment (BAMEX).Observations suggest that the formation and longevity of MCVs depend critically on how the MCV interacts with ambient vertical shear. To further understand this interaction the PI will conduct a combined theoretical, numerical, and observational study that builds on the PI and Co-PI's previous NSF research. The theoretical study will commence by examining the quasi-geostrophic `free' alignment of an idealized MCV. This sets the stage for a key theoretical analysis to determine the critical shear necessary to irreversibly shear apart a given MCV. Knowledge of the critical shear is believed central to distinguishing those MCVs that regenerate convection from those that do not. The impact of new convection triggered by the vortex's resistance to ambient shear will be studied systematically with the goal of determining the feedback of convection on the intensity of the MCV.Observational tests of the theoretical work will be carried out using airborne Doppler radar and dropsonde data from the BAMEX investigation of MCVs. In particular, the evolution of vorticity associated with the MCV and nearby convection will be documented using diagnostic tools previously developed to study the dynamics of the hurricane core and the genesis of tropical cyclones. Presently, no observational data set is yet available detailing the radial vorticity structure of an MCV, the evolution of MCV tilt and intensity, and the development of vorticity in association with regenerated convection, all of which are essential elements of the BAMEX research objectives.Successful completion of this research can potentially provide forecasters with the knowledge needed to extend the prediction time for some times of warm season convective storms.