Studies of Midlatitude Mesoscale Convective Systems

本研究的目的是提高对中纬度中尺度对流系统及其伴随的恶劣天气过程的认识，并最终提高对中纬度中尺度对流系统的预测。特别令人感兴趣的是伴随层状降水区组织模式不同的mcs和产生大风和极端降雨的mcs。目前，与这类系统有关的地面气象特征没有很好的文献记录。为了解决这个问题，首席研究员将利用俄克拉何马州Mesonet（由俄克拉何马州气候调查管理）的地面观测数据，一个记录长度为十年的数据集，来自WSR-88D网络的雷达数据，以及快速更新周期（RUC）分析来研究伴随mcs的地表和环境条件（风、压力、热力学和降水特征），包括拖尾、领先和平行层状降水；弓回声;中尺度对流涡；以及产生极端降雨的mcs。俄克拉何马州Mesonet数据包括5分钟的地表观测，分辨率约为30公里，将能够详细分析中尺度地面压力场。将特别关注MCSs内的中高/低尾流对联。该研究的知识价值源于它将提供与大范围中尺度对流系统相关的结构和物理过程的新认识。具有不同层状降水区域方向（后向、前向和平行）、弓形回波、mcv和产生极端降雨的mcs的地表特征迄今为止仅从有限的案例研究中得到记录。俄克拉何马州Mesonet观测的十年记录现在提供了更全面地确定这种降水系统的大样本的表面特征的机会，从中可以推断出它们的动力学。这项研究的更广泛的影响涉及它将如何提高对mcs和伴随的恶劣天气的理解和最终预测。与一大类MCSs相关的地表特征，有时是直接的，有时是间接的，用来衡量它们在风暴中的严重程度和过程。例如，弓形回波的特征包括极端地面风、由中高/尾流低对联产生的随尾层状降水的mcs，以及沿着风暴产生的流出边界在同一位置新单体的再生而产生的某些极端降雨风暴。认识到这些特征与它们所产生的风暴的关系，对于气象服务的可靠临近预报和短期预报是很重要的。这些风暴每年都会造成重大的生命和财产损失，目前对它们的预测能力很低。这项研究的最终目的是提高这种预测的技能。

The objective of this research is to enhance understanding of processes associated with midlatitude mesoscale convective systems (MCSs) and their accompanying severe weather, and ultimately to improve the prediction of such systems. Of particular interest are MCSs having varying patterns of organization of their attendant stratiform precipitation regions and those producing high winds and extreme rainfall. At present, the surface meteorological features associated such systems are not well documented.To address this problem, the Principal Investigator will utilize surface observations from the Oklahoma Mesonet (administered by the Oklahoma Climatological Survey), a dataset now with a record length of ten years, radar data from the WSR-88D network, and Rapid Update Cycle (RUC) analyses to investigate the surface and environmental conditions (wind, pressure, thermodynamic, and precipitation features) accompanying MCSs with trailing, leading, and parallel stratiform precipitation; bow echoes; mesoscale convective vortices (MCVs); and MCSs that produce extreme rainfall. The Oklahoma Mesonet data, consisting of 5-min surface observations at about 30-km resolution, will enable detailed analyses of the mesoscale surface pressure fields. Particular attention will be focused on mesohigh/wake low couplets within MCSs.The intellectual merit of the research derives from the new understanding it will provide of the structure and physical processes associated with a broad range of mesoscale convective systems. The surface signatures of MCSs having different orientations of their stratiform precipitation regions (trailing, leading, and parallel), bow echoes, MCVs, and extreme-rain-producing MCSs have heretofore only been documented from a limited number of case studies. The ten-year record of Oklahoma Mesonet observations now affords the opportunity to more comprehensively determine the surface signatures of a large sample of such precipitation systems, from which inferences can be made about their dynamics. The broader impacts of the research relate to how it will improve understanding and ultimately prediction of MCSs and accompanying severe weather. The surface features associated with a large class of MCSs are measures, sometimes direct and sometimes indirect, of their severity and processes within the storms. For example, bow echoes are characterized by extreme surface winds, MCSs with trailing stratiform precipitation by mesohigh/wake low couplets, and certain extreme rain-producing storms by regeneration of new cells in the same location along storm-generated outflow boundaries. The recognition of such features in relation to the storms they produce is important to weather services for reliable nowcasting and short-term forecasting. These storms are responsible annually for significant life and property damage, and currently the forecast skill for them is low. This research is ultimately directed toward improving the skill in such forecasts.