Data Processing and Quality Control of the CW193 Sun Photometer Network and Evaluation of Satellite Aerosol Products

Reliable ground-based aerosol observations are essential for evaluating satellite aerosol products across heterogeneous surfaces and aerosol regimes. This study established a six-site CW193 sun photometer network in China with quality-controlled observations from January 2023 to May 2026 and assessed CW193 AOD consistency using collocated CE318 observations at Fujin and Lijiang. A consistent processing chain including Langley calibration, preprocessing, triplet consistency screening, 440 nm daily-stability screening, temporal smoothness tests, and statistical outlier removal was applied, and the sensitivity to QC threshold perturbations was examined. The quality-controlled observations were then used to evaluate the FY-3F/MERSI-III daily AOD product and three MODIS products (MCD19A2, MOD04_L2, and MYD04_L2). Across 440–1020 nm, CW193 and CE318 showed strong agreement (R = 0.979–0.999; slopes = 0.989–1.019; RMSE = 0.007–0.024), with no evident long-term drift during the available comparison periods. At Lijiang, Hebi, and Qingdao, FY-3F/MERSI-III yielded R values of 0.220, 0.664, and 0.702 and RMSE values of 0.128, 0.157, and 0.183, respectively. MODIS performance varied strongly among sites and products; MCD19A2 yielded the lowest RMSE at Dunhuang, Kashgar, and Lijiang, whereas MYD04_L2 yielded the lowest RMSE at Hebi and Qingdao. The small MOD04_L2 and MYD04_L2 matchup samples at Fujin precluded a robust ranking. All three MODIS products substantially underestimated AOD at Kashgar. Regional CW193 observations further distinguished high-AOD, low-AE conditions at Kashgar from low AOD, high-AE conditions at Lijiang. QC threshold perturbations affected data retention more than the principal aerosol and satellite evaluation statistics. These results support CW193 as a regional ground-based reference for satellite AOD evaluation while emphasizing the importance of site conditions, collocation strategy, sampling, and the empirical nature of AOD–AE optical regimes.