VALIDATION AND COMPARISON OF FINE-MODE AEROSOL OPTICAL DEPTH PRODUCTS BETWEEN MODIS AND POLDER
Fine-mode aerosol usually comes from anthropogenic emissions. The fine-mode aerosol optical depth (AOD f) is an important parameter for estimating the particulate matter with an aerodynamic diameter little than 2.5 μm (PM 2.5). Compared to the ground-based observations, AOD f products from satellite remote sensing have an advantage of high spatial coverage, which is suitable for monitoring the air quality at a regional or global scale. Up to now, AOD f products have been released by several sensors, such as the single-angle multi-spectral intensity sensor MODIS and multi-angle multi-spectral polarization sensor POLDER, then what’re the different performances of AOD f products from them? In this study, the different spatial resolution AOD f products respectively from MODIS latest Collection 6.1 (C6.1, 3 and 10 km) and POLDER latest level 2 version 1.01 (L2, 18 km) were firstly compared with each other in Beijing-Tianjin-Hebei (BTH) domains. Then those products were validated against the ground-based AERosol RObotic NETwork (AERONET) measurements, where has been suffering the severe air pollution since decades ago. The comparison of yearly averaged AOD f products between MODIS and POLDER shows a good consistency on the spatial distribution, the higher spatial resolution products of MODIS show more details, both low values of AOD f appeared in the northwest area with small population and industry, high values appeared in the southeast area with lots of cities, industries, and large population. However, the whole yearly AOD f average values of MODIS are higher than that of POLDER. The results of validation against AERONET show that the accuracy of AOD f products at 865 nm from POLDER (R = 0.94, RMSE = 0.05) is high than that at 550 nm of MODIS (3 km: R = 0.69, RMSE = 0.32; 10 km: R = 0.76, RMSE = 0.3). In this study, the performance of different spatial resolutions AOD f products retrieved from the intensity (MODIS 3 and 10 km) and polarized sensors (POLDER 18 km) were evaluated. Those results not only have a great significance to provide users amore appropriate choice of the AOD f products in the BTH region but also display that the accuracy and spatial resolution of MODIS and POLDER AOD f products need to be improved.