Synoptic and Mesoscale Structure and Evolution of Occluded Winter Storms and Their Associated Precipitation Bands

虽然锋面和气旋的大尺度方面已经研究了几年，但区域和局地尺度的特征还不是很清楚。本研究旨在扩展先前关于冬季闭塞气旋的结构、动力学和降水分布的研究。这项工作将通过采用案例研究方法来完成，该方法涉及使用先进的中尺度数值模式对选定事件进行的高分辨率数值模拟的观测分析和输出诊断。研究的一个组成部分将侧重于利用最近在雪带野外实验中收集的前所未有的观测数据集记录暖闭塞的精细尺度结构和降水分布。关于暖闭塞的中尺度结构以及在气旋闭塞区产生和维持大雪带的中尺度动力过程的问题将在这部分研究中得到解决。对封闭区域内地转动力学的研究，以及对封闭象限内静态稳定性演变的研究，也是研究的组成部分。此外，将采用分段位涡度（PV）诊断来具体检查离散PV异常在改变成熟气旋锋面结构中的作用。这项研究的成功完成将在理解对温带气旋的结构、动力和降水分布特征有贡献的过程方面取得重要进展。

While the larger-scale aspects of fronts and cyclones has been studied for some years, the regional and local-scale characteristics are not as well known. This research aims to extend prior studies of the structure, dynamics, and precipitation distribution associated with occluded winter cyclones. This work will be accomplished through employment of a case study approach involving analysis of observations and diagnosis of output from high resolution numerical simulations of selected events performed using an advanced mesoscale numerical model.A component of the research will focus on documenting the fine-scale structure and precipitation distribution of warm occlusions using the unprecedented observational data set collected during the recent SNOWBAND field experiment. Questions regarding the mesoscale structure of warm occlusions as well as the mesoscale dynamical processes responsible for the production and sustenance of heavy snowbands in the occluded sector of cyclones will be addressed in this component of the research.Investigation of the ageostrophic dynamics operating in the occluded sector along with an examination of the evolution of the static stability in the occluded quadrant are also components of the research. In addition, piece-wise potential vorticity (PV) diagnostics will be employed to specifically examine the role of discrete PV anomalies in altering the frontal structure of mature cyclones. Successful completion of this research should produce important advances in understanding of the processes that contribute to the structure, dynamics and precipitation distribution characteristic of extratropical cyclones.