Numerical Simulation and Analysis of Mesoscale Convective Systems and Severe Storms

由于其巨大的经济影响以及对公共安全的重要性，大气对流系统的研究是一个高优先级的研究课题。 根据该奖项，首席研究员将继续研究与对流风暴相关的各种主题。 要解决的具体问题包括：--发展基于雷达的气候学，重点是美国上空中尺度对流系统（MCS）生长阶段对流的时空分布，以表征导致MCS形成的最常见的发展模式，并了解管理不同类别MCS的过程的变化。- 用先进的中尺度数值模式进行敏感性研究，以检查环境控制的相对优势与MCS结构和演变的早期对流强迫的细节。 利用数值模型，研究了土壤水分含量及其不均匀性对MCSs的启动和强度的影响。 使用WSR-88 D多普勒雷达数据，检查特定的derecho（局部大风）事件，以确定它们是否以稳定气团上方的可定义中气旋为特征，并对选定的情况进行数值模拟，以确定导致强风形成的机制。 通过模拟有据可查的龙卷风和零情况，并通过执行进一步的理想化模拟，进一步了解龙卷风形成的过程。 使用简化和复杂的微物理参数化研究两种不同的强风暴类型中冰雹形成的过程。 通过对夜间有组织对流和下午局部强迫对流进行数值敏感性实验，重新检查在城市环境中收集的现有数据。这项研究的成功完成将提高对几种高影响天气的理解和预测能力，包括山洪、龙卷风、大风和严重冰雹。A-i

Due to its large economic impact as well as importance for public safety, the study of atmospheric convective systems is a high priority topic of research. Under this award the Principal Investigator will continue research on a variety of topics associated with convective storms. Specific topics to be addressed include:--Development of a radar-based climatology focusing on the spatial and temporal distribution of convection during the growth stages of mesoscale convective systems (MCS) over the U.S. to characterize the most common patterns of development that leads to MCS formation and to understand the variability of processes governing different classes of MCSs. -- Perform sensitivity studies with an advanced mesoscale numerical model to examine the relative dominance of environmental controls versus the details of early convective forcing on MCS structure and evolution.-- Using a numerical model, investigate the effects of soil moisture amounts and its inhomogeneity on the initiation and strength of MCSs.-- Using WSR-88D Doppler radar data, examine specific derecho (localized high wind) events to determine if they are characterized by a definable mesocyclone over a stable air mass and perform numerical simulations of selected cases to determine mechanisms responsible for severe wind formation.-- Obtain further insight into processes responsible for tornado formation by simulating well -documented tornadic and null cases, and by performing further idealized simu-lations.-- Investigate the processes of hail formation in two distinctive severe storm types using simplified and complex microphysical parameterizations.-- Reexamine existing data collected in the urban environment by performing numerical sensitivity experiments for both nocturnal organized convection and afternoon locally-forced convection.Successful completion of this research will lead to improved understanding and ability to forecast several types of high impact weather including flash flooding, tornadoes, high winds and severe hail.A-i