VALIDATION AND COMPARISON OF FINE-MODE AEROSOL OPTICAL DEPTH PRODUCTS BETWEEN MODIS AND POLDER

Abstract. 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.