梅雨期暴雨系统的中尺度动能谱及可预报性研究

Meiyu period is the frequent occurrence period of heavy rain in China, so forecast capability of heavy rain during this period is closely related to the overall level of heavy rain forecast. Meiyu heavy rainfall results from the interaction of multi-system and multi-scale processes, and can be divided into various types with different heavy rainfall formation systems. In this project, these heavy rainfall systems are taken as the main research objects. Particularly, the formation mechanism and predictability of different types of heavy rainfall are studied from the point view of energy conversion and cascade delivery by using the spectral energy analysis method. Based on the high resolution reanalysis data, different sensitivity experiments are conducted by using the weather research forecasting (WRF) model. The differences of kinetic energy spectra among various heavy rainfall systems and the relationship between the spectral slope of kinetic energy and horizontal wavenumber are revealed by analyzing the characteristics of the atmospheric kinetic energy spectra in the heavy rainfall systems. And the differences of kinetic energy spectra during different development phases of the heavy rain are revealed by the analysis of the variation of kinetic energy spectra. In addition, the energy source of the heavy rainfall development, especially the mechanical responsible for the enhancement of mesoscale kinetic energy, is revealed by the analysis of the formation mechanism of kinetic energy spectra. The effects of moist processes are further investigated througt extending the concept of mosit avaliable poteital energy and conducting the spectral mosit avaliable poteital energy budget analysis. Meanwhile, the contribution of mosit avaliable poteital energy and the latent heating to the kinetic energy budget will be revealed. Moreover, the relationship between the distribution of error energy spectra of heavy rainfall systems with different flow patterns and the heavy rainfall predictability is investigated through the analysis of characteristics and formation mechanism of error energy spectra. All of the results can deepen the understanding of the development mechanism and predictability of Meiyu heavy rain, and provide a theoretical basis for the enhancement of numerical model and improvement of the level of heavy rainfall fine forecast.

梅雨期是我国暴雨天气的频发期，对梅雨期暴雨的预报能力关系到我国暴雨预报的整体水平。梅雨期暴雨是多尺度系统相互作用的结果，其暴雨系统的类型和形成机制具有多样化特征。项目以梅雨期暴雨系统为研究对象，利用能量谱分析方法，从能量转换和串级输送的角度研究暴雨形成机理和可预报性。以高分辨的资料为研究基础，利用WRF模式，通过设计不同的敏感性试验，分析暴雨系统中大气动能谱特征，揭示不同暴雨系统的动能谱差异，阐明梅雨期暴雨系统动能谱斜率与水平波数的关系；分析暴雨演变过程中动能谱变化特征，揭示暴雨发展不同阶段的动能谱差异；研究暴雨系统动能谱形成机理，揭示暴雨系统发展的能量来源，明确中尺度谱段动能增加的物理机制；扩展大气湿有效位能的概念，分析湿有效位能谱特征，进一步研究湿物理过程在中尺度能量收支中的作用，揭示湿有效位能和凝结潜热对动能收支中贡献；分析误差能量谱特征和形成机理，揭示不同类型暴雨系统误差能量谱与暴雨可预报之间的关系。项目结果可以深化对梅雨期暴雨发展机理及可预报性的认识，为改进数值模式和提高暴雨预报水平提供理论依据。

梅雨期是我国暴雨频发期，对梅雨期暴雨的预报关系到我国暴雨预报的整体水平，对其准确预报的前提是了解系统发展演变的动力学机理。由于梅雨锋的多尺度特征及梅雨期暴雨类型和形成机理的多样性，使得从动能转换和串级输送的角度研究暴雨形成机理更为有效。能量谱分析能够得到中尺度能量的演变和来源，从而为揭示中尺度系统发展机理提供新视角。项目以梅雨期暴雨系统为研究对象，采用理论研究和数值模拟相结合的方法，研究了中尺度动能谱特征及其形成机理，其研究结果可深化认识暴雨的发展机理及可预报性，在改进数值模式和资料同化方面有广泛的应用前景。.项目主要研究了湿大气能量动力学理论和中尺度能量谱形成机理。首先推导出了描述湿大气中尺度运动完整的动力学和热力学方程组及其扰动形式。基于基本湿大气方程组推导出了描述湿大气内部运动的改进湿位涡及其倾向方程；定义了湿有效位能、有效弹性势能和各项水物质势能，推导出了各种能量的收支方程及谱方程，给出了湿大气能量能量收支、转换和转移关系。然后基于WRF模式的动力框架，构建了梅雨锋系统和斜压波系统的理想模型，研究了梅雨锋系统和斜压波系统的能量谱分布和演变特征，揭示了不同降水系统在不同高度上中尺度能量谱形成的机理，特别是湿过程在能量串级和能量转换的作用，发现了中尺度动能收支主要依赖于非线性平流项、浮力通量项和气压梯度项，对流激发的重力惯性波对平流层低层中尺度动能谱形成有显著作用。此外，还分析了不同类型暴雨个例的形成机理。基于非线性误差信息熵理论，揭示了Lorenz系统非线性误差增长规律和影响因子，分析了实际大气单变量及联合变量的可预报性，发现了可预报性的区域差异性。研究了可以提高暴雨预报精度的雷达卫星资料同化方法，建立了能提高暴雨预报精度的雷达卫星资料的集合变分同化系统，检验发现基于集合变分方法的雷达或卫星资料的同化能有效提高暴雨的数值预报水平。