Synergistic Retrieval of Multitemporal Aerosol Optical Depth Over North China Plain Using Geostationary Satellite Data of Himawari-8

An N-Dimensional Cost Function (NDCF) method is introduced in this paper to simultaneously retrieve aerosol optical depth (AOD) at multiple time points by exploiting multitemporal data synergy from geostationary satellite. In the proposed method, the number of remote sensing observations used is flexible, the bidirectional reflectance effect is considered, and AOD variation in different observations is allowed. Sensitivity study shows that the relative error of the retrieved AOD decreases as the dimension of the cost function increases. The retrieval accuracy of NDCF method has been improved more than 3 times by changing the dimension of the cost function from 2 to 13. The relative error of the retrieved AOD is less than 20% if viewing zenith angle is less than 70 degrees for dark surface or 60 degrees for bright surface. The proposed method is applied to Advanced Himawari Imager data on board Himawari-8 over North China Plain. Case study shows that the retrieved AOD by NDCF method demonstrates the same time variation tendency with the AErosol RObotic NETwork (AERONET) AOD measurement as well as the similar spatial distribution characteristic with Moderate-resolution Imaging Spectrometer AOD product. The validation result shows that the NDCF method demonstrates the considerable AOD retrieval accuracy in all the three selected AERONET sites of Beijing-Chinese Academy of Meteorological Sciences (CAMS) (slope=0.826, R-2=0.832), XiangHe (slope=0.879, R-2=0.836), and XuZhou-China University of Mining and Technology (CUMT) (slope=0.889, R-2=0.730). The expected error of the NDCF method is estimated as =0.080.19. Compared to the official Himawari product, the NDCF method improves the AOD retrieval accuracy and retrieval applicability over North China Plain of Himawari-8/Advanced Himawari Imager data.