冷涡强对流系统云微物理过程及机理研究

China is facing the urgent need to increase the forecast precision for severe northeast cold vortex (CV) convection. Severe north-China cold vortex (NCCV) convection is one of the most common forms of severe convection in northeastern China, which can cause intense local precipitation, thunderstorm-induced gale-force winds, lightning, hail or even tornadoes. Due to limitations of available observations and investigation tools, previous research on NCCV has mostly focused on the analyses of the synoptic-scale environment and statistical distributions of CV in time and space. Current knowledge and understanding of the microphysical processes leading to heavy precipitation within NCCV are still very limited. In convection-resolving numerical models, precipitation processes are realized through microphysics parameterization (MP). Therefore, accurate MP schemes are essential for numerical prediction of severe convection and associated precipitation...This project will perform high-resolution (~0.5-1km) numerical simulations for select NCCV convection cases using state-of-art multi-moment MP schemes. The forecasts using different MP schemes will be objectively verified against available observations, including those to be collected by special field experiments. The microphysical structure and evolution, the spatial and temporal characteristics of hydrometeor size distributions, and the conversion processes among the cloud microphysical species within NCCV will be quantitatively examined. Conceptual models for NCCV convection will be developed based on the case studies, which will include time evolution of the dynamical structures and key microphysical processes. Through improved understanding of microphysical processes in NCCV convection and identification of deficiencies within certain MP schemes, this project aims to help improve subjective and numerical model-based forecasting of severe weather associated with NCCV convection.

冷涡强对流系统是造成我国北方地区突发性短时强降水、雷暴、冰雹、甚至龙卷等高影响灾害性天气的主要天气系统之一。受观测及研究条件限制，过去冷涡研究主要集中于冷涡发生天气背景及时空分布气候统计，对云微物理过程及降水机理认识十分有限。人们对冷涡强对流系统造成灾害性天气的预报能力亟待提高。对流可分辨模式中，降水物理过程主要由云微物理参数化方案实现，因此其对强对流天气的预报和模拟都至关重要。..本项目将利用目前最先进的多参数微物理参数化方案，对数个北方冷涡强对流个例做高分辨率（约0.5-1km网格距）数值模拟，结合实际观测，定量评估不同微物理参数化方案对冷涡强对流系统的预报能力。着眼云微物理过程对强对流系统发展演变的重要性，研究强对流风暴微物理结构演变、不同相态水物质谱分布的时空变化特征及相互转化机制；旨在构建北方冷涡强对流系统包含动力和微物理过程相互作用的生命史概念模型，以期改进对冷涡强对流天气的预报能力。

东北冷涡强对流系统是诱发我国北方地区高影响性灾害天气的重要天气系统，但我国目前对冷涡强对流系统的触发演变机理及其导致的灾害性天气的预报能力仍有待提高。鉴于此，本项目挑选造成强降雹和地面大风两类灾害的冷涡强对流风暴系统为研究对象，结合卫星、雷达等多源观测资料和高分辨率数值模式，开展冷涡背景下造成冰雹及大风灾害的强对流风暴系统触发及组织演变机理、不同微物理方案对冰雹定量预报及地面大风形成机理的系列研究。.对于冷涡背景下的强对流冰雹风暴，选取2015年4月28日江苏多单体冰雹风暴为研究对象，系统分析了此次冷涡强对流冰雹风暴系统的发展演变过程。敏感性实验显示，一个前行中尺度对流系统降水形成的海上冷池向后扩散，显著影响东海上空的中尺度涡旋的生成及加强。最后提出冷涡强对流冰雹风暴发展、演变及其与前行中尺度对流系统相互作用的概念模型。对于造成地面强风的冷涡强风暴系统，以2021年4月30日南通地面大风为例，详细诊断分析了此次风暴系统的结构组织及低层大范围大风的形成机制。结果显示，此次大范围大风主要发生在我国东南沿海区域，大风来源包括中尺度风暴系统后侧的中层干冷空气入流及阵风锋前侧向后的入流。粒子轨迹追踪显示东南沿海盛行的偏东风将下沉气流向西输送，且弱的东海表面拖拽对大范围大风的形成起重要作用。.此外，基于模拟结果较好的先进三参微物理方案，设计出新的诊断谱形参数的双参方案，经过多组不同强风暴实际个例的模拟测试，证实该方案相比三参方案能节省计算资源，且能较好再现雹暴强度及冰雹粒子谱分布。还设计优化了数值模式中积雪压实层物理过程参数化方案，进一步提高了模式对低层大气条件及地表特征的再现能力。.综上，本项目研究进一步认识了我国突发性冷涡强风暴的典型天气系统配置，揭示了边界层过程在强风暴系统内的确切过程和关键动力热力因素，完善了数值模式云微物理过程及陆面过程参数化方案，可为冷涡强对流业务预报提供科学参考。