State Key Laboratory of Severe Weather (LASW), Institute of Atmospheric Composition, Chinese Academy of Meteorological Sciences, Beijing, 100081, China.
School of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo, 454000, Henan, China.
Chemosphere. 2019 Dec;236:124268. doi: 10.1016/j.chemosphere.2019.06.238. Epub 2019 Jul 2.
This study provided a comprehensive evaluation of the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 006 (C6) and 061 (C6.1) Dark Target (DT) 10 km aerosol optical depth (AOD) over China during 2002-2014. Considering that sparse Aerosol Robotic Network (AERONET) sites are available in China, 18 sites from China Aerosol Remote Sensing Network (CARSNET) were also used to conduct this validation. The results showed that C6.1 DT outperform C6 with 59.03% of the retrievals falling within the expected error (EE) compared to C6 (54.94%). Meanwhile, C6.1 DT achieved a reduced RMSE of 0.171, a higher R of 0.901 and a bias closer to 0 relative to C6 (RMSE: 0.185; R: 0.890). When the validation was conducted over different underlying surfaces, C6 DT overestimated AOD by 19.8%, with only 45.01% of the retrievals within the EE over urban sites, whereas C6.1 showed clear improvements, with 11.8% more data falling within the EE. Hardly any improvement was observed in C6.1 over forest, cropland, and grassland sites. The C6.1 DT exhibited more significant improvements over Beijing area and northern China than southern China. The highest retrieval accuracy of 61.05% among the four Beijing sites was achieved at Beijing_CARSNET, but the improvements were lower than other Beijing sites. The extent of the improvements was positively correlated with the percentage of urban pixels over the sites in Beijing and northern China in terms of the retrieval accuracy. Moreover, C6.1 DT had a little effect on improvements over southern China and showed reduced collocation over coastal cities.
本研究对 2002-2014 年期间中国地区中分辨率成像光谱仪（MODIS）集合 006（C6）和 061（C6.1）暗目标（DT）10km 气溶胶光学厚度（AOD）进行了全面评估。由于中国的气溶胶自动观测网（AERONET）站点稀少，本研究还使用了中国气溶胶遥感网（CARSNET）的 18 个站点进行验证。结果表明，C6.1 DT 的表现优于 C6，有 59.03%的反演结果落在预期误差（EE）内，而 C6 为 54.94%。同时，C6.1 DT 的均方根误差（RMSE）降低了 0.171，相关系数（R）提高了 0.011，偏差更接近 0，而 C6 的 RMSE 为 0.185，R 为 0.890。在不同下垫面进行验证时，C6 DT 高估了 AOD，城市站点有 45.01%的反演结果落在 EE 内，而 C6.1 则有明显改善，有 11.8%的数据落在 EE 内。在森林、农田和草地站点，C6.1 的改进不明显。C6.1 DT 在北京地区和中国北方的改进比中国南方更为显著。四个北京站点中，北京_CARSNET 的反演精度最高，为 61.05%，但改进程度低于其他北京站点。改进程度与北京和中国北方站点中城市像素的百分比呈正相关，特别是在站点的反演精度方面。此外，C6.1 DT 对中国南方的改进作用较小，对沿海城市的匹配度降低。
