回波合并在线状中尺度对流系统生成演变中的作用研究

During the evolution of linear mesoscale convective systems, the echo merger often appear between convective cells or echo bands, which have a major impact on development, maintenance of convective system . The result of echo mergence would bring about Heavy rain, hail and strong winds. It Increase the difficulty of nowcasting to a certain extent. Echo merges with the sudden, large-scale span and so on, but also reflects the interaction between the multi-scale. The high spatial and temporal data which will be used in this research are Doppler radar observations, satellite data and automatic weather station observations. Some techniques and methods ,such as statistics and typical case analysis, Integrated stack of multiple data and Dual-Doppler radar wind retrieval will be applied In this study. At the same time, merger characteristics or self-organizing process of echo will be investigated, and multi-scale characteristics and the spatial structure of variation will be studied during the stage of linear mesoscale convective system formation. The study of wind field and spatial structure before and after the merger between linear mesoscale convective systems and different nature of clouds at the same time to carry out, and the detailed process and mechanism of echo merger will be investigated. Another major research is the impact on the evolution of linear mesoscale convective systems and ground disasters after merging. All these study will provide technical support to improve the short-term nowcasting level of linear mesoscale convective systems.

线状中尺度对流系统演变过程经常出现与对流单体回波（或回波带）间的合并，对系统的发展、维持等产生重要影响，可导致局地致灾性大暴雨、冰雹和大风，临近预报难度大。回波合并具有突发性、尺度跨度大等特点，还体现着多尺度间的相互作用。本项目充分利用新一代多普勒雷达所观测到的实例样本，结合卫星和加密自动站等高时空分辨率的观测资料，采用统计和典型个例分析相结合、多种资料综合叠加、双多普勒雷达风场反演等方法和技术，详细普查线状中尺度对流系统形成阶段回波合并特征（或自组织过程），研究回波合并（或自组织过程）的多尺度特征和空间结构变化特征；研究线状中尺度对流系统与不同尺度、不同性质云团合并前后风场和空间结构变化，探讨回波合并的细致过程和机制，研究合并对线状中尺度对流系统演变和地面灾害产生的影响，为提高线状中尺度对流系统的短时临近预报水平提供技术支撑。

线状中尺度对流系统演变过程经常出现与对流单体回波间的合并，对系统的发展、维持等产生重要影响，可导致局地致灾性大暴雨、冰雹和大风，临近预报难度大。以新一代天气雷达气象产品资料为主，结合天气形势、自动站加密观测资料和灾情报告，详细普查华北中东部线状中尺度对流系统基本特征，以及线状中尺度对流系统形成阶段回波合并、发展演变过程与孤立单体合并、孤立单体间合并的多尺度特征和空间结构变化。针对山东中西部后向发展雷暴的统计特征，给出了常见的３种后向发展雷暴概念模型，分别对３种类型典型后向发展雷暴的演变方式及其物理机制进行了初步分析，加深了对山东中西部后向发展雷暴生成和演变特征的认识；线状中尺度对流系统与孤立单体、单体群和对流带合并，导致线状中尺度对流系统尺度增大、强度增强，或者局部发展得更加强盛，造成局地冰雹、大风等灾害。线状中尺度对流系统演变过程也可以激发新单体、并逐渐合并而促使系统发展加强；对发生在鲁北地区的雹暴类单体合并实例的单体合并成因、合并过程单体结构和合并过程单体径向速度场特征进行了研究，合并后在反射率因子结构特征上出现增强发展，径向速度场辐合区向中低层伸展、发展等，可能预示合并后要出现冰雹、大风等强对流天气，中气旋特征发展旺盛，更接近地面，可能伴有龙卷出现。因此利用连续的雷达观测资料，根据单体移动方向，以及新生单体情况，对可能出现的合并情况及时预警，有可能提高短时临近预报成功率，减少灾害损失。