双偏振雷达探测降水演变的灵敏性的散射机理研究

Dual linear polarization radar is an important means to study of cloud precipitation physics mechanism deeply, and expands the application of radar information in the field of meteorology. Polarization parameters of radar that could estimate the amount and types of hydrometeors accurately, reflect the structure and physical process of precipitation sensitively, has become the essential instrument for studying on the composition and evolution of precipitation. In view of dual polarization weather radar being at the exploratory research stage in China, various theoretical and applied problems need to be solved. Based on the theory of electromagnetic field, the polarization parameters sensitivity and the scattering mechanism during precipitation evolution need to be studied. Because the C band dual polarization radar just to be installed in our university, it is need to study on the data quality control, including the correct extraction of polarization parameters; recognize the phase feature of cloud through the polarization parameters, reveal the physical mechanism of precipitation. According to types and life stages of precipitation, Details of polarization parameters such as Zdr, LDR, Kdp, and the correlation coefficient in PPI and RHI will be analyzed. The comparison polarization parameters with non-polarization parameters quantitatively and qualitatively will be done in sensitivity, details and in advance of physical process of precipitation for understanding the cloud structure and evolution. The project provides more information for the development of China's dual polarization weather radar.

双线性偏振雷达是深入研究云降水物理机制的重要手段，拓展了雷达信息在气象领域的应用。偏振雷达参数可以更准确地估计水凝物类型和数量，敏感地反映降水云体的结构和降水物理过程，已成为研究降水的构成和发展所不可缺少的工具。鉴于双偏振多普勒天气雷达在国内正处于探索研究和应用阶段，需要解决面临的各种理论和应用问题。理论上，根据电磁场理论, 探讨双偏振雷达的各偏振参数在降水演变中的敏感性和散射机理。应用上，根据我校的C波段双线偏振雷达资料，在资料质量控制基础上，研究各偏振参数的正确提取；识别降水云的相态特征，通过各偏振参数的特性揭示降水的物理机制。根据各降水类型及其不同发展演变阶段，分析Zdr、Kdp、LDR以及ρ等偏振参数在PPI和RHI上的精细变化。从定性和定量上比较偏振参数相比于非偏振参数在降水演变过程中的敏感性、细致性和提前性，加深对降水云结构和演变的认识，为我国双偏振天气雷达的发展提供更多依据。

研究双偏振天气雷达对非球形及非均匀相态水凝物的探测敏感性，特别是水平偏振波和垂直偏振波在均匀或非均匀降水介质（如雨滴、冰雹、雪与冰晶等）中引起的散射以及通过这些介质的传播特性。对非球形或非均匀相态的水凝物回波，正确理解双偏振参量（如：差分反射率因子Zdr，差分相位常数Kdp，相关系数CC）所反映的电磁散射理论和实际天气过程的物理意义。..研究双偏振雷达对灾害性天气的探测敏感性、散射机理及回波演变。如强降水超级单体、强冰雹超级单体、冬季冰雹、台风雨带的龙卷、飑线和下击暴流等，发现了冰雹强回波远端TBSS根部的Zdr大值现象并分析了散射机理。结合反射率因子及径向速度，尤其是垂直方向上的气流特征，通过冰水混合相态分布与垂直气流的关系，描述中小尺度对流单体的三维结构及不同发展阶段双偏振参数的演变特征，加深中尺度天气学-雷达气象学-云物理学之间相互关系的整体认识。..研究晴空回波的大气风温湿结构及双偏振参量特征。大气温、压、湿梯度造成折射指数分布不均以及背景风场引起的湍流增强可造成晴空回波，回波机理为湍流衍射。不同的风场及大气湍团干湿特性使晴空回波的Zdr呈现不同特征。提出Zdr大值区在强风背景下的变形湍涡概念，发现Zdr等参量易受到多普勒效应的影响。..双偏振雷达RHI垂直探测可敏感地识别降雪云体冰水相态的精细特征，降雪时6km高度附近的雷达高带是温度在-12℃~-15℃含有冰晶粒子的淞附效应所致；2km高度附近的Zdr高值带及CC的低值带反映了降雪时增温增湿的层云，其上的热力不稳定易促进对流抬升，显示了冬季降雪的高架对流特点。..项目研究结果形成了若干核心及以上的论文和三本专著（《双线偏振多普勒天气雷达探测原理与应用》、《龙卷形成原理与天气雷达探测》和《电磁原理与大气遥感基础》），为我国的学者提供了双偏振参量回波特征的散射机理和实际应用的参考依据。