This article aims to determine the factors that introduce more errors to mountainous aerosol optical depth (AOD) in the hope that such results can guide aerosol inversion over mountainous areas. AODs retrieved by the Generalized Retrieval of Aerosol and Surface Properties (GRASP) algorithm from POLDER-3 are compared with those obtained from Aerosol Robotic Network (AERONET) over global mountainous areas between 2005 and 2013. The comparison between the AODs from GRASP/POLDER-3 (AODGP) and AERONET (AODA) is used to test the performance of the GRASP algorithm. It was found that the accuracy of AODGP is significantly different over variable underlying surfaces with different terrain types, and mountainous AODGP is seriously overestimated. The AODGP values are much less consistent with AODA over mountainous than urban areas for almost all aerosol types, which suggests that the terrain size has a significant impact on aerosol remote sensing. Mountainous AODGP in low latitudes performs better than that in midlatitude as the former is less disturbed by shelters and the shadows of mountain bodies. The performance of AODGP as a function of altitude and slope is similar, where the correlation decreases and the overestimation percentage increases quickly with an increase of slope or altitude. The observation geometry and aerosol profile change as a function of slope and altitude, which impart inaccuracies in the retrieved AOD. Overall, the terrain size is dominant in the multiangular and polarization remote sensing of aerosols and the POLarization and Directionality of the Earth’s Reflectances (POLDER) measurements are sensitive to mountain terrain size. Mountainous slope and altitude disturb the AODGP most seriously, followed by latitude and seasonal variation.

中文翻译：

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山区多角度和偏振卫星测量气溶胶光学深度产品的评估

本文旨在确定导致山区气溶胶光学深度（AOD）误差较大的因素，以期为山区气溶胶反演提供指导。将 2005 年至 2013 年间通过 POLDER-3 的气溶胶和表面特性广义检索 (GRASP) 算法检索到的 AOD 与从全球山区气溶胶机器人网络 (AERONET) 获得的 AOD 进行比较。GRASP/POLDER-的 AOD 之间的比较3（AODGP）和AERONET（AODA）用于测试GRASP算法的性能。研究发现，在不同地形类型的变化下垫面上，AODGP的精度存在显着差异，山区AODGP被严重高估。对于几乎所有气溶胶类型，AODGP 值与山区的 AODA 比城市地区的一致性要差得多，这表明地形大小对气溶胶遥感有显着影响。低纬度山区的 AODGP 表现优于中纬度地区，因为前者较少受到避难所和山体阴影的干扰。AODGP 作为高度和坡度的函数的性能是相似的，其中相关性降低并且高估百分比随着坡度或高度的增加而迅速增加。观测几何和气溶胶剖面随坡度和高度的变化而变化，这会导致反演的 AOD 不准确。全面的，地形尺寸在气溶胶的多角和偏振遥感中占主导地位，地球反射率的偏振和方向性（POLDER）测量对山地地形尺寸敏感。山地坡度和海拔对AODGP的干扰最严重，其次是纬度和季节变化。