煤烟与沙尘混合非球形气溶胶偏振散射特性及其辐射强迫效应研究

Dust and soot are two kinds of aerosols that severely affect the air quality in north China, playing important roles in climate change and human health. However, dust and soot have obvious different chemical and microphysical properties, making big differences in their scattering, optical and radiative characteristics. Therefore, it is necessary to investigate the scattering and radiative effects of dust and soot aerosols, especially their mixtures. Soot particles in atmosphere usually are in the form of fractal aggregates. They easily get aged through being coated by other particles in the form of internal mixing. Few present researches have considered the internal mixing state of soot and dust aerosols in their scattering and radiative properties calculations. This project will start with the micro-morphology of aerosol particles by considering the fractal aggregate and core-shell structures of soot and non-spherical characteristics of dust. Based on the micro-morphological modeling of aerosol particles, TMatrix+Geo methods will be used to simulate and validate the polarized scattering characteristics of non-spherical soot and dust aerosol mixtures. In the macro aspect, by utilizing vector radiative transfer model, the angular distributions of polarization and radiance of non-spherical soot and dust aerosol mixtures at top and bottom of atmosphere could be obtained. Furthermore, the radiative forcing differences of different aerosol mixtures could be investigated. Finally, field experimental data will be used to validate and evaluate the accuracy and uncertainty of non-spherical soot and dust aerosol mixture model.

沙尘与煤烟型气溶胶是影响我国华北地区空气质量的两类重要气溶胶，对气候变化、人体健康都有重大影响。沙尘与煤烟粒子的化学特征、微物理性质区别明显，使得两者散射性质、光学性质乃至辐射性质均有较大的差异。因此，对沙尘与煤烟气溶胶，尤其是两者混合气溶胶的散射性质与辐射效应研究十分必要。大气中煤烟粒子一般呈团簇体状，易老化包裹其他粒子呈内混形式。目前研究内混模式下煤烟与沙尘粒子散射与辐射效应相对较少。本研究拟从粒子微观建模入手，首先考虑煤烟粒子团簇结构与核-壳结构、沙尘粒子的非球形特性，对粒子形态进行建模；采用TMatrix结合几何光学模型模拟沙尘与煤烟粒子混合非球形气溶胶粒子的偏振散射特性并验证。在宏观方面，基于矢量辐射传输模型定量计算其在大气上界及下界的偏振与辐亮度角度分布规律，并进一步探讨不同混合态气溶胶的辐射强迫差异；最后利用实验测量数据对煤烟沙尘混合气溶胶模型的精度与不确定度进行验证与评价。

沙尘与煤烟型气溶胶是影响我国华北地区空气质量的两类重要气溶胶，对气候变化、人体健康都有重大影响。沙尘与煤烟粒子的化学特征、微物理性质区别明显，使得两者散射性质、光学性质乃至辐射性质均有较大的差异。通过本项目执行，课题组主要研究内容和进展包括：1. 开展了不同气溶胶粒子的单次散射性质建模研究，通过几何光学模型、MIE散射模型及TMatrix模型，对不同尺度、吸收性、谱分布的气溶胶粒子进行了单次散射计算，结果发现沙尘型与煤烟型气溶胶粒子的散射特性有较大的差异；2. 开展基于非球形模型的沙尘及煤烟型气溶胶散射性质研究，首先针对大气中可能出现的多气溶胶混合状况，利用SOSRT模型进行模拟，结果显示混合气溶胶不会改变全天空偏振场的模式，但会改变其强度。进一步地，利用不同下垫面的性质，进行了煤烟与沙尘混合气溶胶的全天空偏振模式图敏感性分析，结果显示不同吸收性的气溶胶产生的偏振效应差别极大；3. 开展了煤烟沙尘混合气溶胶辐射强迫效应及实验验证研究，开发了一种新的考虑了多波段效应的辐射强迫效应计算方法。通过本项目的执行，我们在气溶胶粒子的微观、宏观性质上均取得了较明显的进步，并初步应用于生态环境研究中，本项目所获得的参数、方法、结论为进一步的应用研究提供了坚实基础，并将通过后续项目的支持持续开展。