Studies of Midlatitude Mesoscale Convective Systems

这项研究的目的是加强对与中纬度中尺度对流系统(MCSs)及其伴随的恶劣天气相关过程的了解，并最终改进对这类系统的预报。特别令人感兴趣的是其伴随的层状降水区和产生大风和极端降雨的MCS具有不同组织模式的MCS。目前，与这类系统相关的地面气象特征还没有很好的记录。为了解决这个问题，首席调查者将利用俄克拉荷马中层网(由俄克拉荷马气候调查局管理)的地面观测、WSR-88D网络的雷达数据和快速更新周期(RUC)分析来调查伴随着MCSs的地面和环境条件(风、气压、热力学和降水特征)以及伴随着拖尾、领先和平行的层状降水、弓形回波、中尺度对流涡旋(MCV)和产生极端降雨的MCSs。俄克拉荷马州中尺度网的数据，包括大约30公里分辨率的5分钟地面观测，将能够对中尺度地面压力场进行详细分析。这项研究的学术价值来自于对与广泛的中尺度对流系统相关的结构和物理过程的新的理解。到目前为止，层状降水区(拖尾、领先和平行)、弓形回波、MCV和极端降雨产生的MCS具有不同方向的MCS的表面特征仅从有限数量的案例研究中得到记录。俄克拉荷马州梅索网观测的十年记录现在提供了更全面地确定这类降水系统的大样本的表面特征的机会，由此可以对它们的动力学做出推断。这项研究的更广泛影响涉及到它将如何提高对MCS和伴随而来的恶劣天气的理解和最终预测。与一大类MCS相关的地表特征是它们在风暴中的严重性和过程的量度，有时是直接的，有时是间接的。例如，弓形回波的特征是极端的地面风，MCSs通过中高/尾迹低对伴随着层状降水，以及某些极端的暴雨产生的风暴是通过沿风暴产生的流出边界在同一位置再生新的单体而产生的。认识到这些特征与它们所产生的风暴有关，对于天气服务提供可靠的即时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，目前对它们的预测技能很低。这项研究的最终目的是提高此类预测的技能。

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.