Yasir E. Mohieldeen^1,, Ranya Elsheikh², Sarra Ouerghi²

This study evaluates the accuracy of monthly MODIS Terra and Aqua Collection 6.1 Level 3 aerosol optical depth (AOD) products- combining Dark Target and Deep Blue algorithms at 550 nm- against ground-based AERONET Version 3 Level 2 measurements at eight active stations located in and near arid regions. Satellite and AERONET monthly AOD values were compared using linear regression. Results show strong correlations for both platforms: Terra (r = 0.844, R² = 0.712) and Aqua (r = 0.828, R² = 0.685). Both sensors exhibit similar positive biases relative to AERONET (+0.083 for Terra, +0.082 for Aqua), indicating that MODIS tends to overestimate AOD. Terra shows slightly greater overestimation but better captures monthly variability than Aqua. Performance varies notably by station, likely reflecting differences in local aerosol composition, surface reflectance, coastal versus desert heterogeneity, and spatial mismatches between point-based AERONET measurements and MODIS's coarser 1° grid cells. Overall, MODIS monthly AOD products provide valuable data for regional-scale aerosol monitoring in dust-prone Middle Eastern environments. However, the study emphasizes that station-specific calibration and cautious interpretation are necessary when applying coarse-resolution MODIS data to localized dust and air-quality assessments, given the observed spatial variability in accuracy.

MODIS, Terra, Aqua, AERONET, aerosol optical depth, Monthly AOD