Impact of Aerosol Vertical Distribution on Aerosol Optical Depth Retrieval from Passive Satellite Sensors
Impact of Aerosol Vertical Distribution on Aerosol Optical Depth Retrieval from Passive Satellite Sensors
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DOI：
10.3390/rs12091524
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
Chong Li;Jing Li;O. Dubovik;Z. Zeng;Y. Yung
中科院分区：
文献类型：
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作者：
Chong Li;Jing Li;O. Dubovik;Z. Zeng;Y. Yung
当从无源卫星传感器反演气溶胶光学深度（AOD）时，通常需要假设气溶胶的垂直分布，这可能会导致反演的不确定性。在本研究中，我们以中分辨率光谱辐射计 (MODIS) 和可见红外成像辐射计套件 (VIIRS) 传感器为例，研究气溶胶垂直分布对 AOD 反演的影响。使用具有不同气溶胶剖面和表面条件的辐射传输模型进行了一系列灵敏度实验。假设AOD为0.2，我们发现AOD反演误差对吸收气溶胶的垂直分布最敏感；气溶胶尺度高度的 −1 km 误差可能导致约 30% 的 AOD 反演误差。此外，对于这种气溶胶类型，忽略边界层的存在可能会进一步导致约 10% 的 AOD 反演误差。同一列内散射气溶胶和吸收气溶胶的垂直分布差异也可能导致-15%（散射气溶胶高于吸收气溶胶）至15%（散射气溶胶低于吸收气溶胶）误差。表面反射率在影响 AOD 检索误差方面也起着重要作用，通常较亮的表面误差较高。还讨论了与 AOD 检索错误相关的物理机制。最后，在VIIRS反演算法中，将默认的指数剖面替换为北大站点微脉冲激光雷达观测到的气溶胶垂直剖面，反演的AOD与地面观测结果吻合得更好，相关系数从0.63增加到0.83，偏差从0.15减少到0.03。我们的研究强调了气溶胶垂直剖面假设在卫星 AOD 反演中的重要性，并表明考虑更现实的剖面有助于减少不确定性。
When retrieving Aerosol Optical Depth (AOD) from passive satellite sensors, the vertical distribution of aerosols usually needs to be assumed, potentially causing uncertainties in the retrievals. In this study, we use the Moderate Resolution Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) sensors as examples to investigate the impact of aerosol vertical distribution on AOD retrievals. A series of sensitivity experiments was conducted using radiative transfer models with different aerosol profiles and surface conditions. Assuming a 0.2 AOD, we found that the AOD retrieval error is the most sensitive to the vertical distribution of absorbing aerosols; a −1 km error in aerosol scale height can lead to a ~30% AOD retrieval error. Moreover, for this aerosol type, ignoring the existence of the boundary layer can further result in a ~10% AOD retrieval error. The differences in the vertical distribution of scattering and absorbing aerosols within the same column may also cause −15% (scattering aerosols above absorbing aerosols) to 15% (scattering aerosols below absorbing aerosols) errors. Surface reflectance also plays an important role in affecting the AOD retrieval error, with higher errors over brighter surfaces in general. The physical mechanism associated with the AOD retrieval errors is also discussed. Finally, by replacing the default exponential profile with the observed aerosol vertical profile by a micro-pulse lidar at the Beijing-PKU site in the VIIRS retrieval algorithm, the retrieved AOD shows a much better agreement with surface observations, with the correlation coefficient increased from 0.63 to 0.83 and bias decreased from 0.15 to 0.03. Our study highlights the importance of aerosol vertical profile assumption in satellite AOD retrievals, and indicates that considering more realistic profiles can help reduce the uncertainties.