多种下垫面湍流扩散特征的对比研究

Atmospheric pollution becomes a significant problem in recent years. For pollution control, we should firstly make sure of the dispersion ability of atmosphere. In surface layer, pollutants are dispersed and transported primarily though turbulence. Turbulence in surface layer is greatly affected by underlying surfaces, which makes the difference of turbulent dispersion between on various underlying surfaces. However, the theories and models of turbulent dispersion are mostly established according to the experiments on homogeneous underlying surface, which can not be often used on complex terrains. Turbulent dispersion on complex terrains has been studied by experiments and simulations, but it is not understood why turbulent dispersion is different between various underlying surfaces. Therefore, it is necessary to compare the characteristics of turbulent dispersion between on various underlying surfaces and find out of the rule of turbulent dispersion on complex terrains, which will be carried out in this project with the data collected from experiments on atmospheric dispersion on various terrains, including city, costal, desert, plain, hill. We will apply footprint method into calculation of dispersion parameters, and deeply study the dispersion parameters in order to characterize turbulent dispersion on various underlying surfaces. The difference of dispersion parameters on various underlying surfaces and the reason of the difference are our focus. The result of this project can be a reference for the improvement of models and the modification of relevant guidelines of atmospheric environment impact assessment.

近年来，大气污染问题凸显。污染控制首先要弄清楚大气的扩散能力。近地层污染物的输送扩散主要通过湍流运动。湍流运动受下垫面的影响很大，导致不同下垫面的湍流扩散特征有所不同。然而，目前的湍流扩散理论和模型大多基于平坦均匀下垫面的实验结果得到，在复杂下垫面往往不适用。尽管对复杂下垫面湍流扩散特征已有各种实验和模拟研究，但是，各种下垫面扩散特征差异的机理并不清楚。因此，需要对各种下垫面的湍流扩散特征进行比较分析，研究不同下垫面的湍流扩散规律。本项目利用多年来在各种下垫面（城市、滨海地区、沙漠地区、内陆平原地区、内陆山区等）的大气扩散实验结果，引入印痕函数，从扩散参数的计算入手，对复杂下垫面扩散特征进行深入分析，比较各种下垫面扩散参数的差异并分析其原因。本项目的研究结果可以为扩散模式的改进和相关环境影响评价导则的修改提供依据。

近年来，大气污染问题凸显。污染控制首先要弄清大气的扩散能力。近地层污染物的输送扩散主要通过湍流运动。湍流运动受下垫面的影响很大，导致不同下垫面的湍流扩散特征各有不同。然而，目前的湍流扩散理论和模型大多基于平坦均匀下垫面的实验结果得到，在复杂下垫面往往不适用。尽管对复杂下垫面湍流扩散特征已有各种实验和模拟研究，但是，各种下垫面扩散特征差异的机理并不清楚。因此，需要对各种下垫面的湍流扩散特征进行比较分析，找出其中的异同点，从而得出不同下垫面的湍流扩散规律。本项目收集了沿海和内陆13处典型的复杂下垫面（海洋-丘陵、海洋-农田、海洋-沙漠、沿江山地、水库-丘陵、沿江开阔平原等）测风塔不同高度超声风速仪观测资料和示踪试验资料，以及其它大气扩散试验观测资料。对比分析了不同下垫面冬夏季不同高度湍流强度、湍涡结构特征、扩散参数、边界层风温垂直分布特征等大气扩散特征。总结了湍流强度随风速、风向、层结、季节变化的一般规律和下垫面特征差异和风速对湍涡结构的影响，引入印痕函数分析了不同下垫面测风塔的代表性范围，以及其不同积分阈值对扩散曲线的影响，并通过与示踪试验对比，分析给出了不同下垫面超声风速仪资料的预处理方法和特征扩散时间尺度的确定方法。这些结果对于复杂下垫面超声风速仪资料的处理和扩散参数的计算均具有参考意义。