2011-2016年中国极端降水事件中尺度特征统计分析

To advance the understanding of detailed evolution of extreme precipitation event in China and the underlying physical mechanisms governing its initiation and development is of scientific and practical importance. Previous studies on extreme precipitation in China have mainly investigated the trends and mean climatology, or analyzed the synoptic and mesoscale dynamical causes of representative cases using numerical modeling. However, statistical analysis of the mesoscale features for a large number of extreme precipitation events over the extensive region of China is rather limited in literature. Therefore, it is necessary to further investigate the temporal and spatial characteristics of the detailed evolution and mesoscale development of extreme precipitation events over a variety of regions in China..This project will collectively use the minutely surface observations collected at the densely distributed surface meteorological observation stations, 6-min radar reflectivity data, weather maps, and sounding data to analyze the following aspects of extreme precipitation events occurred in China (east of 96°E longitude) during 2011-2016..(a) Detailed evolutional features of precipitation during individual extreme events such as temporal evolution of instantaneous (5-min) rainfall intensity..(b) Structural and movement features of extreme-rain-producing mesoscale systems in terms of composite radar reflectivity..(c) Surface mesoscale features such as cold outflow boundaries and convergent lines that are of critical relevance to the initiation and development of extreme-rain-producing convective systems..(d) Relationships between the mesoscale features and both the synoptic background and the thermodynamics-and-dynamics of environmental atmosphere..Through the aforementioned analysis, this project aims to reveal the multi-scale characteristics of extreme precipitation events in China, which will improve the current understanding of physical mechanisms and the established conceptual model, and provide the scientific basis for improving forecast skill for extreme precipitation events in China.

深刻认识我国极端降水事件的细致演变及发生发展的物理机制具有重要的科学价值和现实意义。以往研究我国极端降水着重分析气候变化趋势和气候平均统计特征，或对个例进行数值模拟探讨天气尺度和中尺度动力学成因，而对我国广大区域的大量个例进行中尺度统计分析的研究还不多，有必要进一步分析不同地区极端降水精细化演变特征和中尺度发生发展机制的时空分布。.因此，将利用稠密的地面气象站分钟级观测资料和业务天气雷达逐6分钟反射率资料、天气图、探空资料，分析2011-2016年我国96°E以东广大地区极端降水事件的瞬时雨强时间演变等基本特征，分析降水系统的组合反射率宏观结构和移动，分析出流边界、地面辐合线等对流系统的地面中尺度触发和发展机制，分析中尺度特征与天气背景和环境大气热动力状况的关系，旨在获得极端降水事件这些多尺度特征的时空分布，完善已有的物理机制认识和概念模型，为提高我国极端降水的精细化预报水平提供科学基础。

深刻认识我国极端降水事件的细致演变及发生发展的物理机制具有重要的科学价值和现实意义。本项目研究了我国华南、西南和长江三角洲地区的极端降水事件。主要包括：.1、利用“华南季风降水实验”获取的多平台联合观测资料及VDRAS四维变分同化分析技术，分析广州“5.7”破纪录极端降水中小尺度动力和微物理精细结构，揭示了季风海岸的城市群等复杂下垫面，对流反馈以及云和气溶胶等多因子、多尺度系统对产生极端短时强降水的协同作用；分析2011-16年暖季珠三角城市群地区24次极端小时降水事件，获得了弱天气强迫下粤港澳大湾区局地短时强降水及对流的时空特征，利用耦合多层城市冠层模型的WRF模式揭示了地形、城市群、海岸线等复杂下垫面的单独和协同影响及其机理；以2014年5月11日深圳、珠海一带的极端降水事件为例，证明浅薄中尺度出流边界对近洋面暖湿不稳定空气的抬升作用，发现弓形雨带快速分裂、重建过程；利用1km、6min分辨率雷达基数据，首次构建了华南前汛期大样本MCS数据集，揭示了华南地区MCS的时空分布和演变特征。.2、分析2020年我国十大天气气候事件之一的四川盆地持续性强降雨事件，揭示了强降水持续性及日变化特征显著的成因；揭示西南地区1981−2017年突发性暴雨事件发生频次、强度和持续时间的时空分布特征。.3、分析了1975-2018年夏季长三角地区极端小时降水气候态、变化以及2011-2018年夏季113起局地发生的非台风型极端降水事件，表明强城市热岛对城市群关键区（尤其是上海─苏锡常城市带）极端小时降水发生频次升高有重要贡献。