Abstract

Use of multi-angle sensors, which can perform ground observations in different view directions, provides an important technical means to acquire more comprehensive and detailed remote sensing information. This study explored the effect of angle changes on satellite-based aerosol optical depth (AOD) retrieval using 2016–2018 Multi-angle Imaging SpectroRadiometer (MISR) data in the Yangtze River Delta. The Moderate resolution Imaging Spectroradiometer (MODIS) surface reflectance determined by the MODIS V5.2 algorithm and MODIS BRDF data are used to obtain MISR surface reflectance at different angles after a spectral conversion between MODIS and MISR, and then MISR AOD with different angles were retrieved based on the MISR surface reflectance at different angles. Moreover, the errors and their formation mechanism in retrieving AOD using MISR remote sensing data at different angles were analyzed based on the Global Aerosol Robotic Network (AERONET) ground observations. We used six indicators, including correlation coefficient (R), significant level (P value), mean absolute error (MAE), mean relative error (MRE) root mean square error (RMSE) and relative mean bias (RMB), and AERONET AOD is used to verify the MISR AOD. The results show that at Taihu and Xuzhou stations, the highest R values are 0.81 (Aa AOD) and 0.75 (An AOD), and the minimum RMSE values at Taihu and Xuzhou-CUMT stations are 0.11 (Aa AOD) and 0.20 (An AOD), respectively. Incorrect surface reflectance measurement is the root cause of the angle effect in MISR AOD retrieval. With the same surface reflectance deviation, the larger the MISR observation angle, the closer the retrieved MISR AOD is to the AOD observed by AERONET. The AOD retrieval of the forward observation angle is closer to AERONET AOD than that of backward observation angle, and the retrieved error is greatest at the vertical angle (nadir). Therefore, sensors for vertical ground observation are not suitable for AOD retrieval, and sensors in non-vertical directions, especially forward to the ground, are more favorable to MISR AOD retrieval.

摘要

利用多角度传感器，可以进行不同视角的地面观测，为获取更全面、更详细的遥感信息提供了重要的技术手段。本研究利用长三角地区 2016-2018 年多角度成像光谱辐射计 (MISR) 数据探讨角度变化对星基气溶胶光学深度 (AOD) 反演的影响。利用MODIS V5.2算法确定的中分辨率成像光谱仪（MODIS）表面反射率和MODIS BRDF数据，在MODIS和MISR光谱转换后获得不同角度的MISR表面反射率，进而反演不同角度的MISR AOD基于不同角度的 MISR 表面反射率。而且，基于全球气溶胶机器人网络（AERONET）地面观测，分析了不同角度使用MISR遥感数据反演AOD的误差及其形成机制。我们使用了六个指标，包括相关系数（R）、显着性水平（P值）、平均绝对误差（MAE）、平均相对误差（MRE）均方根误差（RMSE）和相对平均偏差（RMB），以及AERONET AOD用于验证 MISR AOD。结果表明，太湖站和徐州站的R值最高分别为0.81（Aa AOD）和0.75（An AOD），太湖站和徐州-CUMT站的最小RMSE值分别为0.11（Aa AOD）和0.20（An AOD） ）， 分别。不正确的表面反射率测量是 MISR AOD 检索中角度效应的根本原因。在相同的表面反射率偏差下，MISR 观测角度越大，检索到的 MISR AOD 与 AERONET 观测到的 AOD 越接近。前向观测角的 AOD 反演比后向观测角的 AOD 反演更接近 AERONET AOD，且反演误差在垂直角（最低点）处最大。因此，垂直地面观测的传感器不适合AOD反演，非垂直方向的传感器，尤其是前向地面的传感器，更有利于MISR AOD反演。