基于VIIRS DNB通道反演夜间气溶胶光学厚度研究

Aerosol is a major uncertain factor in the global climate change assessment and Aerosol Optical Depth (AOD) is a common parameter to character aerosol loading. However, only extensive studies on AOD are in daytime from satellite remote sensing, e.g. MODIS, but is mere in nighttime. Recently, there is possibility to retrieved nocturnal AOD from Visible/Infrared Imager/Radiometer Suite (VIIRS) Day/Night Band (DNB) observations by city artificial light attenuation. To feed the great need of reliable and wide spatial coverage of nighttime aerosol product, we are intent to analyze the interaction of moonlight, city artificial light, atmosphere and satellite, propose to a “background” method to retrieve AOD using the contrast between regions with and without artificial surface lights, and develop a “adjacent pixel” method by examination of the dispersion of radiance values above an artificial source in adjacent pixel. The influence of city scale, surface character and aerosol type on the two methods will be also evaluated and validated by ground-based measurement from lunar photometer. At last, nocturnal AOD products are retrieved in 6 years of 5 sites (e.g. Beijing) from VIIRS/DNB measurements, their temporal and spatial variance is also propose to analyzed. It will be a breakthrough compared with single AOD value retrieval in one city currently, and provide a new approach for aerosol remote sensing, climate change studies, regional air quality forecast and so on.

气溶胶是全球气候变化评估中最大的不确定性因子。气溶胶光学厚度（AOD）是表征气溶胶含量的重要参量，而目前利用卫星大范围反演气溶胶光学厚度仅在白天研究广泛，夜间却很少见到。最新研究表明，利用VIIRS传感器DNB通道观测的夜晚城市灯光反演气溶胶光学厚度是一种可能的手段。基于此，为获取面覆盖的城市夜间AOD，本项目利用辐射传输模拟月光、城市灯光、大气和卫星的相互作用，构建利用城市灯光和郊区暗目标差异的“背景光”反演模型，以及利用城市相邻像元灯光差异的“邻近像元”反演模型，分别评估城市大小、地表特征、气溶胶类型等对两种模型的影响，并利用月亮光度计观测结果进行验证。最后项目将反演北京等5个站点共6年的夜间气溶胶光学厚度，并分析他们的时空分布变化。本项目反演城市区域内夜间气溶胶光学厚度空间分布，突破目前一个城市仅能反演单个AOD数值的瓶颈，为夜间气溶胶观测、气候变化评估、区域空气质量预报提供新途径。

本项目面向夜间气溶胶光学厚度大面积遥感观测的迫切需求，针对目前夜间微光卫星可见光波段反演气溶胶特性存在的突出问题，重点研究利用城市灯光反演气溶胶光学厚度遥感方案，为获取面覆盖的城市夜间AOD，本项目利用辐射传输模拟月光、城市灯光、大气和卫星的相互作用，构建利用城市灯光和郊区暗目标差异的“背景光”反演模型，以及利用城市相邻像元灯光差异的“邻近像元”反演模型，分别评估城市大小、地表特征、气溶胶类型等对两种模型的影响，并利用月亮光度计观测结果进行验证。最后项目将反演北京等典型站点多年的夜间气溶胶光学厚度，并分析他们的时空分布变化。本项目反演城市区域内夜间气溶胶光学厚度空间分布，突破目前一个城市仅能反演单个AOD数值的瓶颈，为夜间气溶胶观测、气候变化评估、区域空气质量预报提供新途径。