Continued Analysis of Convective System Evolution Using Convection-permitting Grid Spacing Weather Research and Forecasting (WRF) Simulations

该研究小组将研究中尺度对流系统（mcs）的可预测性和高级演化，并探索旨在改善这些系统的定量和概率降水预测的技术，这些系统是美国中部及其相关农业带暖季降雨的关键来源，既有益又有时有害。研究将侧重于采用2-4公里细网格“对流允许”网格间距（CAGS）的数值模式模拟，该网格间距明确表示雷暴尺度环流和相关降水过程。计划进行两个主要的研究重点。第一部分将强调理解天气研究与预报（WRF）模式对夜间低空急流（LLJ）、行星边界层（PBL）演化和层状雨区发展的模拟中存在的错误，以及这些特征如何影响模拟的MCS演化。第二次推力将涉及评估与低空喷射强度有关的基本问题及其在MCSs发展中所起的作用。内部WRF模拟的大量档案，外部合作者运行的模拟输出，以及来自各种观测来源的数据将被合并，其智力价值集中在对：(1)LLJ模拟精度与MCSs预测的关系的理解；(2) PBL内云-太阳辐射不足对MCS模拟的影响；(3)云微物理和近风暴风对MCS演变的预测作用；(4)评价邻域方法在集成输出中的应用，以提高对流降水预测。这项研究的更广泛影响将通过对暖季对流预报的预期改进来实现，由于恶劣天气和洪水事件的破坏性，这将带来可观的社会效益。研究人员计划与美国国家海洋和大气管理局/国家气象局的工作人员密切合作，以增加对工作操作方面的研究。教育也将得到重视，多名学生参与研究。

This research team will investigate the predictability and upscale evolution of mesoscale convective systems (MCSs) and explore techniques designed to improve quantitative and probabilistic precipitation forecasts of these systems, which serve as a pivotal source of both beneficial and sometimes damaging warm-season rainfall over much of the central U.S. and its associated agricultural belt. Research will focus on numerical model simulations employing fine-mesh "convection-allowing" grid spacings (CAGS) of 2-4 km which explicitly represent thunderstorm-scale circulations and related precipitation processes. Two main research thrusts are planned. The first will emphasize understanding the errors present in simulations from the Weather Research and Forecasting (WRF) model of the nocturnal low-level jet (LLJ), planetary boundary layer (PBL) evolution, and stratiform rain region development and how these features impact simulated MCS evolution. The second thrust will involve evaluations of basic issues related to low-level jet intensity and the role they play in the growth of MCSs. An extensive archive of in-house WRF simulations, output from simulations run by outside collaborators, and data from various observational sources would be incorporated, with intellectual merit centered on advancement of the understanding of (1) relationship of LLJ simulation accuracy to prediction of MCSs; (2) impacts of cloud-solar radiation deficiencies within the PBL on MCS simulations; (3) the role of cloud microphysics and near-storm winds on prediction of MCS evolution; and (4) evaluation of neighborhood methodologies applied to ensemble output to improve convective rainfall prediction.Broader impacts of this research will come through expected improvements in forecasts of warm-season convection, which bring considerable societal benefit due to the disruptive nature of severe weather and flooding events. The researchers plan to work closely with NOAA/National Weather Service personnel to increase the research to operations aspect of the work. Education would also be emphasized, with multiple students involved in the research.