登陆台风内核区降水非对称结构的多普勒雷达观测研究

China is one of the countries suffering most from typhoon damages, and heavy precipitation associated with　typhoons causes great economy losses every year.Due to the lack of high-resolution observations in the past,asymmetric precipitation structures in the inner core region of landfalling typhoons have been little studied. With the deployment of the operational Doppler radar network over mainland China and Taiwan in recent years,many high- resolution Doppler radar datasets on landfalling typhoons have been collected. Based on these data sets and through detailed retrieval and diagnostic analysis, we will study the asymmetric precipitation structures and the distribution of convection as well as their changes in the inner core region near landfall, and the relationship between asymmetries and typhoon circulation. We will further examine how the combined effects of the primary external forcing factors (including vertical wind shear, storm motion and sea-land contrast)and typhoon internal dynamics(with a focus on vortex Rossby waves) on the asymmetric precipitation structures in the inner core of typhoons.The goal of this study is to improve our understanding of the evolution and mechanism of heavy rain in the inner core of typhoons, and the skills of quantitative precipitation prediction for landfalling typhoons.

我国是世界受台风影响最为严重的国家之一，每年因台风造成的强降水都会给都会给社会经济发展带来严重损失。过去受观测的限制，对于登陆台风内核区的降水结构特征了解相当有限。本课题将借助我国东南沿海和台湾地区多普勒天气雷达网收集的高时、空分辨率台风观测数据，研究台风登陆前内核区降水非对称结构和演变的特征、对流的分布和演变特征，探讨降水非对称和环流非对称结构的关系，深入理解降水非对称结构与主要的台风外部强迫（垂直风切、台风移动、海陆强迫差异）和内动力强迫（涡旋Rossby波）因子的关系，促进对台风内核区强降水发展规律和成因的认识，以改善现有登陆台风定量降水预报能力。

本项目按照研究计划,利用我国沿海多普勒天气雷达网收集的高时、空分辨率台风观测数据，研究台风登陆前内核区降水非对称结构和演变特征及其原因。 首先，分析16个台风内核区降水和对流非对称结构的变化，揭示台风内核区降水存在显著波数1和2的不对称结构，且非对称的能量比值随台风强度的增强而减弱。外部强迫（垂直风切变、移动和海陆强迫差异）对降水非对称贡献约为内动力强迫（涡旋罗斯贝波）的2倍。在中强垂直风切变环境下，垂直风切对登陆台风眼墙降水不对称结构起主导作用，对流多在顺风切右侧激发，至顺风切左侧成熟、降水最强，到逆风切时开始减弱；在弱风切环境下，台风移动是主要因子，最大入流和降水发生均在移动的前侧。海陆下垫面的差异只是加强了降水非对称性，并没有本质上改变非对称的分布。与华南相比，华东地区复杂地形与台风环流相互作用,会显著影响台风降水的非对称结构。然而，对同一台风，不同地形对台风降水的影响机制却存在显著差异。进一步结合雨滴谱和双偏振雷达资料，揭示我国登陆台风降水由高浓度的小粒子组成，雨滴收集云滴是强降水形成的主要微物理过程。这些研究成果加深了对中国登陆台风内核区强降水发展规律和成因的认识，也为验证台风数值模拟结果和改进现有登陆台风定量降水预报能力建立了基础。