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

由于中尺度对流涡旋（MCVs）的寿命和组织对流的能力，它们一直是研究的重点，旨在改善暖季大范围强降水事件的预测。 虽然在过去的十年中已经取得了进展，确定有利于MCV生成的条件，并在连接加强MCV对流再生在其附近，动力学过程管理MCV的生命周期仍然没有得到很好的理解。 为了更好地预测与MCV相关的潜在洪水事件，需要对MCV如何形成以及如何使它们在不利的环境流中保持一致性有基本的了解。 首席研究员（PI）将在弓回声和MCV实验（BAMEX）的主持下解决这两个问题。观察表明，MCV的形成和寿命主要取决于MCV如何与环境垂直切变相互作用。 为了进一步了解这种相互作用，PI将在PI和Co-PI之前的NSF研究的基础上进行综合理论，数值和观察研究。 理论研究将从检查理想化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，以确定不可逆地剪切分离给定MCV所需的临界剪切力。 临界切变的知识被认为是区分那些再生对流的MCV与那些不再生对流的MCV的核心。 将系统地研究由涡旋对环境切变的阻力引发的新对流的影响，目标是确定对流对MCV强度的反馈。将利用BAMEX对MCV调查的机载多普勒雷达和下投式探空仪数据对理论工作进行观测测试。 特别是，与MCV和附近对流相关的涡度演变将使用以前开发的诊断工具来研究飓风核心的动力学和热带气旋的成因。 目前，还没有观测数据集详细说明MCV的径向涡度结构，MCV倾斜和强度的演变，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。成功完成这项研究可能会为预报员提供必要的知识，以延长暖季某些时段的预报时间对流风暴

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.