基于地基偏振遥感观测的粗细模态气溶胶复折射指数反演研究

The lack of knowledge of aerosol parameters, especially for the fine-mode aerosol characters, is one of the main factors that lead to the uncertainty of the aerosol direct climate effect assessment and hinder the quantitative remote sensing of aerosol components. This research intends to retrieve the complex refractive index of fine and coarse mode aerosols from ground-based polarization remote sensing measurements. In this study, multi-parameter forward simulation and parameter sensitivity analysis is set up based on the vector radiative transfer model considering the particle size distribution and the complex refraction index of coarse and fine mode aerosols. Then the inversion scheme based on multi-parameter least squares inversion strategy and the priori knowledge estimation and smooth constraint scheme is established. At the end, a self-consistency study and the accuracy analysis will be used to validate the inversion scheme, and some typical polarization observations from ground-based sunphotometer measurements will be used to test the application of the inversion scheme established in this project. This research can obtain the complex refractive index of fine and coarse mode aerosols in the whole atmosphere column based on spherical and non-spherical particle scattering modeling for the first time. And in the future, the inversion schedule proposed in this project can provide technical support for the study on aerosol composition and analysis on source apportionment of atmospheric particulates.

对气溶胶参数，尤其细粒子气溶胶参数认识不足是导致目前气溶胶直接气候效应评估不确定性偏高和阻碍气溶胶成分定量遥感发展的主要因素之一。本项目拟基于地基偏振遥感观测实现粗、细模态气溶胶复折射指数的反演。本研究考虑粗、细模态气溶胶粒子谱分布和复折射指数，基于矢量辐射传输模型进行多参数前向模拟及敏感性分析；采用多参数最小二乘反演策略、先验知识估计和光滑性约束方案，增加偏振观测信息，建立粗细模态气溶胶复折射指数反演方案；并对该反演方案的闭合性、精度及适用情况进行分析。本项目率先获得整层大气粗、细模态气溶胶复折射指数信息，并在粗、细模态中分别考虑了非球形粒子的散射特性。本项目研究可为未来进一步基于粗细模态气溶胶参数确定气溶胶成分以及来源信息提供技术支撑。

大气气溶胶复折射指数用于描述整层大气气溶胶的散射和吸收特性，是影响短波辐射平衡和气候变化评估的重要参数，准确获得大气气溶胶复折射指数对降低气溶胶引起的气候变化评估不确定性有重要意义。.本项目系统性开展了利用地基偏振遥感观测实现粗细模态气溶胶粒子复折射指数的反演的研究。首先，项目团队发展了地基气溶胶观测设备的高精度偏振定标方法和近红外波段温度效应校准方法，实现了连续高质量偏振观测数据采集。第二，通过收集和整理现有的AERONET，SONET，CARSNET等观测网中国区域地基观测数据，建立了海盐、沙尘以及中国典型区域的气溶胶参数散射模型，获取了分模态复折射指数反演中的关键变量及其先验知识库。第三，将气溶胶粒子群分离为细模态和粗模态，基于辐射传输模型、先验知识和最优化反演方案，构建了分模态气溶胶复折射指数反演方案，并完成了反演方案的闭合性测试；最后将构建的反演方案应用于SONET观测网中国典型区域，实现了中国主要区域分模态复折射指数的反演研究，获取了更详尽的粗细模态气溶胶复折射指数信息。.本项目的研究成果可进一步应用于更精细化的气溶胶成分反演以及气溶胶颗粒物溯源，验证大气化学模式和气溶胶气候效应的评估。