Collaborative Research: Profiling of Winter Storms

关于温带气旋“逗号”部分内降水的空间和时间变异性的过程仍然知之甚少。这部分斜压风暴系统往往是危险冬季天气的焦点，包括大雪、暴风雪和冰暴，这些天气显著影响交通和其他人类活动。该调查组试图通过解决2008-09年和2009-10年冬季开展的冬季风暴(犁)野外作业中出现的悬而未决的问题，来增进我们对该区域内降水次级结构的了解。在耕作过程中收集的观测数据包括NSF/NCARC C-130飞机收集的大量现场微物理数据，怀俄明大学云雷达和C-130上搭载的激光雷达对降水结构进行的高分辨率远程采样，来自地面雷达和剖面系统的补充图像，以及特殊的连续雷达发射。通过适用于与广泛观测的降水子结构进行比较的高分辨率模拟，将获得更多的见解。计划中的研究将集中在：(1)产生云顶生成单元的不稳定的性质和来源，包括确定上升气流的大小、过冷水在云顶附近冰粒生成和增长中的来源和作用、生成单元内的冰颗粒浓度和相关的降水羽流，以及导致在犁过程中观察到的相当普遍的生成单元结构的过程；(2)在以逗号头部暖侧深度垂直高空对流为特征的区域内产生位势不稳定的方法、在暖锋表面上移动的“干槽”对流层高层气流之间的关系，以及伴随锋生的天气尺度垂直运动在触发这种不稳定的释放中的作用的确定；(3)线性降水带的起源及其可能通过天气尺度形变作用于由高空生成单元发出的下沉冰粒羽流而产生的可能性，以及这些带内外不同的冰粒特征；(4)偏振雷达信号与现场测量的微观物理性质的关系，特别是确定过冷水或其影响(例如，边缘粒子)是否可以通过遥感可靠地探测到；(5)层状与对流云区流动的性质，注意细尺度波特征、锋面界面及其对微物理过程的影响，以及它们与产生局地增强型降水率的等熵面、切变不稳定性和低层锋面的关系。这一努力的智力价值在于充分利用独特和广泛的PLORS项目数据集，以比迄今可能的更全面和更明确的方式解决冬季气旋内降水的性质和来源的长期问题。这项研究的更广泛影响将包括精心设计的本科生和研究生教育的组合，以及测试改进的冬季天气系统遥感操作战略，这些战略取决于新兴的观测资产，包括NOAA新升级的双极化WSR-88D雷达网络。预期的较长期影响包括提高数值模式模拟冬季风暴降水亚结构的能力，将其直接应用于造福公众的预报，以及征聘有资格进行大气实地研究的新科学家。

Processes governing the spatial and temporal variability of precipitation within the "comma head" sector of extratropical cyclones remain poorly understood. This sector of baroclinic storm systems is often the focus of hazardous winter weather including heavy snowfall, blizzards and ice storms that markedly impact transportation and other human activities. This investigative team seeks to improve our understanding of precipitation substructures within this zone by addressing outstanding questions arising from the Profiling of Winter Storms (PLOWS) field campaign, which was carried out during the winters of 2008-09 and 2009-10. Observations collected during PLOWS included extensive in-situ microphysical data gathered by the NSF/NCAR C-130 aircraft, high-resolution remote sampling of precipitation structures by the University of Wyoming Cloud Radar and Lidar carried aboard the C-130, complementary views from ground-based radars and profiling systems, and special serial rawinsonde launches. Additional insights will be gained through high-resolution simulations suitable for comparison with a wide range of observed precipitation substructures. Planned investigations will center on: (1) The nature and source of instability creating cloud top generating cells, including determination of updraft magnitudes, origins and role supercooled water in the generation and growth of ice particles near cloud top, ice particle concentrations within generating cells and associated precipitation plumes, and processes leading to the rather ubiquitous generating-cell structures observed during PLOWS; (2) the means by which potential instability is generated within zones characterized by deep upright elevated convection on the warmer side of comma-head regions, the relationship between the "dry-slot" upper-tropospheric airstream moving over warm-frontal surfaces, and determination of the role of synoptic-scale vertical motions accompanying frontogenesis in triggering release of this instability; (3) the origins of linear precipitation bands and their potential creation by synoptic-scale deformation acting upon descending ice particle plumes issued by elevated generating cells, as well as differing ice particle characteristics within and outside these bands; (4) the relationship of polarization radar signatures to measured in situ microphysical properties, and in particular determination of whether supercooled water or its effects (e.g., rimed particles) can be dependably detected via remote sensing; and (5) the nature of stratiform- vs. convective-cloud region flows with attention to fine scale wave features, frontal interfaces, their effects on microphysical processes, and their relationship to isentropic surfaces, shearing instability, and low-level fronts in the production of locally-enhanced precipitation rates.The intellectual merit of this effort rests on full exploitation of the unique and extensive PLOWS project dataset to address longstanding questions concerning the nature and origins of precipitation within winter cyclones in more complete and definitive ways than has heretofore been possible. Broader impacts of this research will include a carefully designed mix of undergraduate and graduate education and testing of improved operational strategies for remote sensing of winter weather systems hinging on emerging observational assets including NOAA's newly-upgraded dual-polarization network of WSR-88D radars. Anticipated longer-term impacts include improved ability of numerical models to simulate precipitation substructures in winter storms with direct application to forecasts benefiting the public, as well as recruitment of new scientists qualified to undertake atmospheric field research.