不同沙源地区起沙关键参量及对流起沙的精细实验与模拟研究

Dust emission during dust-storm events is a complex and nonlinear physical process, which is influenced by many factors. The energy and material exchange between the ground and atmosphere and the atmospheric conditions are the important factors and the basic foundation for dust emission. Dust emission flux and its thresholds, are the basic to model and forecast dust events, but difficult to be precisely estimated. From the different views of blown sand physics and micro-meteorology, this project attempts to understand and observe the process of dust emission generated by wind erosion, carry out field experiments and make parameterization of dust emission over different dust source regions, set up the uniform and feasible criteria standards for dust emission, supplement the information of different types of soils in dust source areas, obtain size-resolved dust particles and their fluxes, focus on the research of convective turbulent dust emission (CTDE), to improve the simulation of dust distribution in the atmosphere. This project contributes to the validation and improvement of parameterization schemes of dust emission, the better understanding of different mechanisms of dust emission, and the setup of the dataset on dust particles of different sizes over various dust source regions, and supports the study of micro-meteorology and land surface process in desert regions..

沙尘天气是一个复杂的物理过程。地气间湍流运动是影响沙尘进入大气的重要和关键因素，是理解起沙机制的重要基础。沙尘释放是非线性的复杂过程，影响因子众多，准确估算起沙通量和阈值一直是科学难题，决定了沙尘天气模拟和预报结果。 本申请利用不同沙源地区沙尘天气综合观测实验，开展起沙过程沙尘气溶胶浓度的时空分布特征研究；从风沙物理学和微气象学的不同角度，探究风蚀起沙过程的理解、研究方法和观测手段的异同。开展不同典型沙源地区沙尘天气精细观测和起沙参数化研究；获取不同沙尘粒径起沙通量和起沙阈值，尝试建立统一的起沙判据；开展对流起沙（Convective Turbulent Dust Emission, CTDE）研究，改善大气沙尘气溶胶分布的模拟。 本研究可为改进和验证起沙参数化方案和数值模拟提供基础，为加深理解起沙机理提供参考，为研究沙尘颗粒物谱分布规律提供基础，丰富沙漠地区微气象学和陆面过程数据支撑。

本研究针对沙尘天气过程起沙通量的定量获取和起沙机理的研究不足，依托沙尘源区之一的科尔沁沙地沙尘暴实验站，开展了微气象学和风沙物理学野外连续的综合观测实验，获取了沙尘天气过程的气象要素、大气湍流和沙尘气溶胶实测资料；完善了沙尘气溶胶湍流通量测量系统，并申请了发明专利；确定了摩擦速度（风速）的起沙阈值范围；确定了适用于科尔沁沙地跃移起沙和对流起沙的判据，指出高发生频次的对流起沙事件释放的沙尘气溶胶对大气气溶胶背景浓度有重要贡献，以往对对流起沙释放沙尘气溶胶研究的不足，导致了沙尘气溶胶的辐射效应存在低估；给出了科尔沁沙地跃移起沙和对流起沙过程释放的沙尘气溶胶粒径分布及特征；解释了土壤湿度对起沙过程及沙尘气溶胶释放的影响；描述了沙尘气溶胶进入大气的物理过程，修正和改进了破碎理论及其方程表达式，改进和验证了新的对流起沙参数化方案；将希尔伯特-黄变换技术应用于大气湍流研究，揭示了科尔沁沙地地区间歇性湍流对热量通量的影响。本研究结果可为提高沙尘预报水平、沙尘暴预警和减灾防灾能力提供科学基础，同时也为沙尘源区陆面过程参数化，特别是迄今为止报道很少的沙源地区沙尘气溶胶实况和对流起沙提供数据基础。