Collaborative Research: Profiling of Winter Storms

对热带气旋“逗点头”区域内降水的时空变异性的控制过程仍然知之甚少。 斜压风暴系统的这一部分往往是危险的冬季天气的焦点，包括严重影响交通和其他人类活动的大雪，暴风雪和冰暴。 该调查小组旨在通过解决2008-09年和2009-10年冬季进行的冬季风暴（PLOWS）实地活动中出现的悬而未决的问题，提高我们对该区域内降水子结构的理解。在PLOWS期间收集的观测数据包括NSF/NCAR C-130飞机收集的大量现场微物理数据，C-130上携带的怀俄明州大学云雷达和激光雷达对降水结构的高分辨率远程采样，地面雷达和剖面系统的补充视图，以及特殊的系列探空仪发射。 通过高分辨率模拟将获得更多的见解，适合与广泛的观测到的降水子结构进行比较。计划的研究将集中在：（1）产生云顶生成单元的不稳定性的性质和来源，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起源和作用、生成单元内的冰粒浓度和相关的降水羽流，以及导致PLOWS期间观测到的相当普遍的生成单元结构的过程;（2）在逗号头部暖侧的垂直深层上升对流区产生潜在不稳定的方式，在暖锋面上移动的“干槽”对流层上层气流之间的关系，以及确定伴随锋生的天气尺度垂直运动在触发这种不稳定释放中的作用;（3）线性降水带的起源和它们可能是由天气尺度变形作用于由高架生成单体产生的下降冰粒羽流而产生的，以及这些带内外不同的冰粒特征;（4）偏振雷达特征与测量的原位微物理性质的关系，并且特别是确定是否存在过冷水或其影响（例如，有边缘的粒子）可以通过遥感被依赖地检测;（5）层状云区与对流云区流动的性质，注意细尺度波特征，锋界面，它们对微物理过程的影响，以及它们与等熵面，剪切不稳定性，和低层次的前线，在生产当地-提高降水率：这项工作的智力价值在于充分利用独特而广泛的PLOWS项目数据集，以解决有关冬季降水的性质和来源的长期问题比迄今为止可能的更完整和更明确的方式。 这项研究的更广泛的影响将包括精心设计的本科和研究生教育的组合，以及对冬季天气系统遥感的改进操作策略的测试，这些策略取决于新兴的观测资产，包括NOAA新升级的WSR-88 D雷达双极化网络。预期的长期影响包括提高数值模型模拟冬季风暴降水子结构的能力，直接应用于有益于公众的预报，以及招聘有资格从事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.