This study aims to evaluate the accuracy of the MODIS C6 and C6.1 Aerosol Optical Depths (AOD) from Terra and Aqua satellites over the two sites located in the urban and coastal regions of Turkey. This is the first study in Turkey focusing on comparison of MODIS Dark Target (DT) C6 and C6.1 AOD against AERONET AOD to provide a better understanding of applicability and suitability of MODIS products under different surfaces and aerosol loadings. Analysis was performed with direct comparisons between MODIS DT AOD retrievals with 3 km and 10 km resolutions and Aerosol Robotic Network (AERONET) Version 3 Level 2 ground-based observations at site scale. Meanwhile, the spatial and temporal variations were also compared and discussed. Accuracy of the spatially and temporally collocated AOD retrievals was analyzed with the correlation coefficient (R), normalized mean bias (NMB), the root mean square error (RMSE), and the expected error (EE) (0.05% + 20%) and (0.05% + 15%) of the DT 3 km and 10 km algorithm over land, respectively. The C6.1 showed better accuracy than the C6 with the higher number of the retrievals falling within the expected error (EE). The C6.1 DT exhibited more significant improvements over the urban site than the coastal site, but both the DT 3 km and 10 km products did not show satisfactory performance with the lower percentages of the retrievals falling within EE (ranging from 36.7% to 50.6%), that was less than one standard deviation confidence interval over the urban site. Moreover, C6.1 DT had a little effect on improvements over the coastal site. Higher percentages of the retrievals falling within EE (ranging from 80.2% to 90.7%) were found at the coastal site. The effects of the surface reflectance based on NDVI and SSA parameter for understanding the aerosol type effect on aerosol retrievals were also discussed. Underestimation of the AOD over the coastal site indicated an inaccurate assumption in the aerosol model. Highly absorbing aerosols also caused overestimation over the urban site. This study suggests that further improvements are required to provide better estimates of satellite-based AOD over urban areas of Turkey.

这项研究旨在评估位于土耳其城市和沿海地区两个地点的Terra和Aqua卫星的MODIS C6和C6.1气溶胶光学深度（AOD）的准确性。这是土耳其的第一项研究，重点是将MODIS暗靶（DT）C6和C6.1 AOD与AERONET AOD进行比较，以更好地了解MODIS产品在不同表面和气溶胶载荷下的适用性和适用性。通过直接比较分辨率为3 km和10 km的MODIS DT AOD与站点规模的Aerosol机器人网络（AERONET）第3版2级地面观测进行了分析。同时，还对时空变化进行了比较和讨论。利用相关系数（R）分析了时空并置的AOD检索的准确性，地面上DT 3 km和10 km算法的归一化平均偏差（NMB），均方根误差（RMSE）和预期误差（EE）（0.05％+ 20％）和（0.05％+ 15％），分别。C6.1与C6相比显示出更好的准确性，而更多的检索次数落在预期误差（EE）内。与沿海地区相比，C6.1 DT在城市地区的改善更大，但DT 3 km和10 km产品均未表现出令人满意的性能，EE范围内的取水百分比较低（从36.7％降至50.6） ％），小于市区范围内的一个标准差置信区间。此外，C6.1 DT对沿海地区的改善影响不大。在沿海地区发现属于EE范围内的取回百分比较高（从80.2％到90.7％）。还讨论了基于NDVI和SSA参数的表面反射率对理解气溶胶类型对气溶胶回收的影响。沿海地区AOD的低估表明气溶胶模型中的假设不正确。高度吸收的气溶胶也导致城市地区的高估。这项研究表明，需要进行进一步的改进以更好地估算土耳其市区的卫星AOD。