转动拉曼-米偏振激光雷达气溶胶微物理特性精确测量方法研究

Measurement of aerosol is very important for the researches of radiation budget of earth-atmosphere system, variability of weather and climate, and air pollution. Lidar, as an effective remote sensing instrument for aerosols detection, has been widely studied with advantage in the temporal and spatial resolution and accuracy. Due to the limited measured parameters, existing Lidar systems often introduce several assumptions and ignore some complex effects such as multiple scattering, etc. in the inversion algorithm. Thus there is non-ignorable error in specific conditions just like moderate aerosol concentration, which can reduce the accuracy and reliability of the measurement results..The project will study the method of measuring accurate aerosol microphysical properties by using the rotational Raman scattering and polarized-Mie scattering signals. Many microphysical properties of aerosol can be derived from high and low level rotational Raman signal, orthogonal Mie polarization channel, and multiple fields of view measurement, with the help of the theory study of Lidar signal, Mie scattering and multiple scattering. Making use of these data, the measurement result will be more accurate and stable, and less affected by the assumptions. Moreover, one can complete the system calibration combining with sounding and satellites data. Based on the above, the issue can provide reliable means of sustained observation of tropospheric aerosols, as well as studies of distribution evolution of aerosols.

气溶胶的测量是研究地气系统辐射收支，天气和气候变化以及大气环境污染的重要方向。激光雷达作为一种气溶胶的有效遥感手段以其在时空分辨率以及测量精度上的优势得到了广泛研究。现有激光雷达系统在气溶胶的测量中往往由于所测参数有限而在反演中引入多种假设，并且忽略多次散射等效应，从而在中等气溶胶浓度等情况下存在较大误差，影响了测量精度和可靠性。.本项目研究利用转动拉曼和米偏振激光雷达精确测量气溶胶微物理特性的方法。利用高低阶转动拉曼通道、正交米散射偏振通道以及系统的多视场角测量结果，结合雷达信号、米散射理论和多次散射理论的模型研究，减少假设的影响和校正多次散射等带来的误差，并结合探空和星上数据进行的定标，可以提高气溶胶多种微物理特性测量结果的精确度和稳定性。本课题可以提高激光雷达观测气溶胶的准确度和可靠性，为实现激光雷达对对流层气溶胶的长期观测、气溶胶的分布演化研究等提供可靠的探测手段。

气溶胶是影响大气和气象的重要因素，获得了科学家的广泛关注。而激光雷达是当今气溶胶观测最为重要的实验手段之一，它所能获得的气溶胶时空分布廓线等数据可以为大气和气象研究提供有力的支持，但是米散射激光雷达由于只有一个通道，在反演中存在着较大的不足，因此本项目提出利用转动拉曼-米偏振激光雷达对气溶胶微物理特性的精确测量开展新方法研究。.本项目主要完成了以下工作：.1、完成了转动拉曼米偏振激光雷达的系统改进，完成了转动拉曼米偏振激光雷达测量气溶胶退偏比的修正算法研究，通过转动拉曼通道信号对偏振通道中的大气分子信号进行修正可以直接获得气溶胶的体退偏比，修正后的结果可以获得最高35%的精度提升；.2、完成了纯转动拉曼测量大气温度廓线的新的标定算法研究，通过对纯转动拉曼散射正反斯托克斯通道非对称状态的修正，在低信噪比环境下大气温度数据反演精度可以获得50%的提升；.3、完成了结合星载CALIPSO信号对拉曼-米偏振激光雷达气溶胶后向散射系数测量的标定算法研究，反演获得的后向散射系统的精度和几何因子与现有的算法相比都有约10%的提升；.4、完成了北京地区重雾霾天气的一次连续观测实验，通过气溶胶的信息分析了大气边界层和高层能见度等物理参数。.项目基本完成了预定任务，发表了9篇SCI/EI检索的论文，其中7篇为SCI检索，包括了ACP，JGR等大气类的顶级期刊。.项目完成的这些工作为激光雷达气溶胶的观测和反演开展了较为深入的理论和算法研究；为拉曼米激光雷达测量气溶胶和大气参数提供了更精确的方法。