动态光散射高光谱激光雷达精细探测大气边界层内温度脉动廓线研究

Temperature fluctuation is one of important parameters for atmospheric turbulence. Sensible heat and latent heat flux are affected by the detecting precision of temperature fluctuation. At present, obtaining temperature fluctuation profile is difficult by using one measurement instrument with fast response, placed in one fixed point or put in flight equipment. In this project, we present a method for the detection of temperature fluctuation profile by employing high-spectral-resolution lidar and photon correlation spectroscopy. The researches are focused on the following four key contents, including the fine detecting method of temperature fluctuation profile, the characterization method of the transient variation of average speed for the thermal movement of gas molecules based on photon correlation spectroscopy, the real-time inversion method of temperature fluctuation profile, detecting experiment and checking method. Finally, the high correlation detection data of temperature fluctuation profile, detecting twice in 1 second and the sensitivity of 0.1 K, is obtained. The research provides the reliable data support for the characteristics and evolution law of temperature fluctuation, and atmospheric boundary layer structure. There are important significances for the more knowledge of turbulent conveying features in atmospheric boundary layer, aerodynamic and thermodynamic characteristics, and interaction mechanism. In addition, there are significant social benefits for the evolution of the atmosphere, the proliferation and removal of pollutants, the improvement of the forecast accuracy of urban disasters, and the stabilization and change of global climate.

温度脉动作为湍流参数中重要的物理量之一，其探测数据的准确性直接影响感热及潜热通量。目前，快速响应测量仪器的原位布点或置于飞行设备上，短时间获得大气温度脉动廓线困难。本项目提出结合高光谱激光雷达与光子相关光谱技术探测温度脉动廓线的方法，重点研究温度脉动廓线精细探测方法；基于光子相关光谱的气体分子热运动平均速率瞬时变化的表征方法；脉动廓线的实时反演方法；脉动廓线探测实验及探测精度校验方法四个方面。最终实现1周探测与探测灵敏度0.1K的大气边界层温度脉动廓线上相关性高的探测数据。研究成果为探索温度脉动特征、演变规律及对大气边界层结构的研究提供可靠的数据支撑；也对进一步认识大气边界层湍流输送特征、大气动力和热力特征及相互作用机理具有极其重要的实际意义。并对于整个大气的演变过程，污染物的扩散和清除，提高城市灾害天气预报准确率，全球气候的稳定与变迁都有着极为重要的影响和显著的社会效益。

针对大气边界层内温度脉动廓线的探测需求，项目首先研究了基于光子相关光谱技术的散射光谱测量方法，利用光子相关光谱技术与大气粒子的布朗运动特性，建立了散射谱宽与光强的自相关函数，通过动态光散射的实验系统，及基于小波变换的信号仿真方法，获得了不同条件下的动态光散射信号，进而获得了测量预设参数，并通过可温控的大气模拟箱，验证了不同温度下的自相关函数；其次利用大气分子与温度的依存关系的瑞利散射测温方法，及光的偏振特性和法布里珀罗标准具的高分辨率光谱特性，构建了一套全偏振高光谱分辨率激光雷达探测系统，并开展大气温度的实验研究，由于同时利用法布里珀罗标准具的透、反射光谱及偏振光的透射特性，结合极化隔离技术抑制了Mie散射信号和太阳背景光，利用50mJ脉冲能量和250mm的望远镜，实现了探测高度夜间4km，白天2.5km的大气温度廓线的精细探测，结果与无线电探空仪的数据吻合，提高了探测性能和测量精度，根据外场大气温度数据与湍流理论，结合野点剔除、去势和归一化处理，获得了温度脉动数据与能谱，数据符合高斯分布，能谱曲线斜率满足著名的柯尔莫哥洛夫的-2/3规律；最后提出了一种基于干涉理论，结合深度扩展和全息再现图自融合的同轴全息测量大气粒子速度的方法，以验证大气温度脉动数据，方法实现了同时提取8张全息图内记录的粒子速度，与传统的两帧曝光法相比，速度提取效率提升了3倍，参考粒子增加到8个，提高了具有复杂运动轨迹粒子的配准精度。项目实现了大气边界层内温度脉动廓线的探测，数据可为探索温度脉动廓线特征、演变规律及对大气边界层结构的研究提供可靠的数据支撑；也对认识大气边界层湍流输送特征、大气动力和热力特征及相互作用机理具有极其重要的实际意义。研究成果对于整个大气的演变过程，污染物的扩散和清除，提高城市灾害天气预报准确率，全球气候的稳定与变迁都有着极为重要的影响和显著的社会效益。