吸收性气溶胶对卫星反演对流层臭氧总量的影响和订正方法研究

The tropospheric ozone is of great significance in understanding the spatial and temporal distribution of atmospheric ozone and its precursors. Valuable tropospheric ozone information can be extracted from Backscattered UltraViolet (BUV) measurements that observed by nadir-viewing hyper-spectral instruments, due to the wavelength dependent ozone absorption in the Hartley and Huggins bands and temperature-dependent ozone absorption structures in the Huggins bands. But the simplified method of aerosol correction still introduces significant errors. On the other hand, tropospheric ozone, as the main target of the new generation of multi-band satellites, still lacks the discussion and characterization of aerosol effects on tropospheric ozone retrieval. Therefore, this project focuses on characterizing the effect of aerosols, especially the absorption aerosols on the tropospheric ozone column retrieval. Forward model which couples the vector radiative transfer mode (VLIDORT), linearized Mie scattering model and rotational Raman scattering model is established to simulate the radiance and weighting functions under various scenarios, in ultraviolet, polarization and visible band. Then the direct and indirect effects of aerosol parameters including optical parameters, vertical distribution and micro-physical parameters are analyzed by using optimal estimation technique. Parameterization schemes for simultaneous retrieval of tropospheric ozone and aerosol are proposed to improve the tropospheric ozone inversion algorithm. Finally, we will apply the updated algorithm to TROPOMI data, and optimize the algorithm iteratively through the validation using ozonesondes, ground-based MAXDOAS and other campaign data. The results can also be applied to similar space-based instruments such as EMI and FY-3.

对流层臭氧观测对于了解我国大气臭氧及其前体物的时空分布具有重要意义。利用高光谱对地观测卫星定量反演对流层臭氧总量已经实际应用并获得了有价值的资料，但是过于简化的气溶胶订正方法仍引入显著的误差。另一方面对流层臭氧作为新一代多波段卫星主要探测目标，仍缺乏关于气溶胶影响的讨论。因此本项目关注气溶胶特别是吸收性气溶胶如何影响对流层臭氧总量反演。为此，建立正演模型（耦合了矢量辐射传输模式、线性化米散射模式和转动莱曼散射模式）模拟分析多种情景下紫外、偏振和可见光等臭氧敏感波段气溶胶光学参数、垂直分布、微物理参数的直接和间接影响。在上述工作基础上，提出利用多个波段同时反演对流层臭氧和气溶胶的参数化方案，改进对流层臭氧反演算法。利用TROPOMI卫星数据进行反演实验，最终利用探空数据、地基遥感数据和机载观测验证反演结果，迭代优化算法。成果也可以应用于我国高分卫星搭载的EMI和风云三号卫星等类似载荷。

本项目构建了紫外、可见光和近红外波段的正演辐射传输模型。该模型耦合了VLIDORT、线性化Mie散射模型、大气分子转动拉曼散射的模型，实现大气分子的散射（弹性和非弹性）和吸收，云和气溶胶粒子的散射和吸收，地表的反射计算。建立基于查找表方法的大气分子拉曼散射快速计算方法，分析了气溶胶光学厚度、单次散射反照率、气溶胶层高度和气溶胶层厚度对弹性散射和非弹性散射的敏感性。研究了利用大气Ring效应反演气溶胶参数的可行性。研发了基于拉曼散射和O4吸收的云顶高度反演算法，提高了对流层臭氧反演精度。利用哨兵-5号 TROPOMI和高分5号EMI光谱数据开展对流层臭氧和二氧化硫反演算法研究。卫星反演的对流层臭氧总量与FTS和探空数据表现出很好的一致性，均值偏差和标准偏差为-1.9±4.76 DU，-4.3±9.69 DU。最后基于OMI臭氧反演数据分析中国地区臭氧及其前体物分布和变化趋势，分析了中国及周边地区对流层臭氧柱总量的空间分布及其随时间的变化以及重点地区臭氧趋势的季节变化。