热带气旋边界层结构的精细化模拟研究

Accurate understanding of the tropical cyclone boundary layer processes is the basis of precise tropical cyclone forecast. However, due to the fact that reliable observation data of tropical cyclone boundary layer are difficult to obtain, combining the observational data and the numerical simulation data becomes an indispensable method to study the tropical cyclone boundary layer. In the past, the conventional boundary layer schemes based on Reynolds average were always used in tropical cyclone simulation, but for the incapability of this kind of schemes in simulations with resolutions higher than kilometer scales, nowadays fine-resolution tropical cyclone simulations with large eddy simulation technology has become an international hot topic. This project will first select tropical cyclone real cases which have been well covered by observation for a relatively long time, and then conduct fine-resolution large eddy simulations with these tropical cyclone real cases to investigate the impacts of different subgrid closure schemes, grid scales and vertical resolutions on the simulation results; after that, with the fine-resolution tropical cyclone large eddy simulation results, 100-m resolution tropical cyclone boundary layer meteorological elements data can be gathered to analyze the physical state and physical processes in the tropical cyclone boundary layer; at last, the modelling capacities of the large eddy simulation schemes and the conventional boundary layer schemes are evaluated in the resolution grey zone (i.e., grid resolution between about 100 and 1000 meters), the rationality of the tropical cyclone boundary layer simulation results in resolution grey zone from the two kinds of schemes will be assessed, and for the unreasonable results of the two kinds of schemes, practical methods will be proposed to circumvent their limitations.

准确认识热带气旋边界层过程是精确预报热带气旋状态的基本前提。然而由于难以获得可靠的热带气旋边界层观测数据，综合使用观测和数值模拟数据成为研究热带气旋边界层的重要手段。过去人们常使用基于雷诺平均的常规边界层方案对热带气旋进行模拟，但是由于这类方案不适用于公里尺度以上的高分辨率模拟，因此基于大涡模拟技术的热带气旋精细化模拟研究已成为国际热点。本研究将首先选取观测覆盖时间较长的热带气旋个例进行精细化大涡模拟实验，研究不同的次网格闭合方案、网格尺度及垂直分层对模拟结果的影响；随后基于热带气旋精细化大涡模拟结果，提取具有百米尺度分辨率的热带气旋边界层气象要素数据，分析热带气旋边界层中的物理状态和物理过程；最后探讨大涡模拟方案和常规边界层方案在模式分辨率灰色地带（即约一百米至一公里的区间）中的模拟能力，诊断两类方案在灰色地带中热带气旋边界层模拟结果的合理性，并针对不合理之处进一步提出可行的改善手段。

项目组对观测资料进行了质量控制，选取了一组热带气旋实例，随后基于这些实例研究了不同的次网格闭合方案、网格尺度及垂直分层对热带气旋模拟结果的影响，并基于大涡模拟结果提取了具有百米尺度分辨率的热带气旋边界层气象要素数据，分析了热带气旋边界层中的物理状态和物理过程，发现了台风中的龙卷风尺度涡旋，探讨了大涡模拟方案和常规边界层方案在模式分辨率灰色地带中的模拟能力，诊断了两类方案在灰色地带中热带气旋边界层模拟结果的合理性，最后提出了海气表面层通量算法改进方案。