Evaluation of the representativeness of ground-based visibility for analysis the spatial and temporal variability of aerosol optical thickness in China

Aerosol trends is an important factor in climate changes. Visibility is considered as an alternative information to investigate the long-term aerosol loadings. However, few studies analyzed the representativeness of visibility on AOT. In this paper, surface visibility, MODerate-resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR) monthly AOT products between July 2002 and December 2014 were analyzed to extract the dominant modes of variability using Singular Value Decomposition (SVD) method. Result indicates that the AOT and visibility agree well in term of interannual variability. Large differences were observed in seasonal variability between visibility and AOT. Aerosol vertical distribution from LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies (LIVAS) and cloud data from ground-based meteorological station were used to explain the disagreement. Seasonal aerosol vertical distribution variations is the main reason and cloud contamination also played important role. Good agreement were found between the low level AOT from LIVAS and visibility for all regions. The result in this study highlight that visibility can only reflect interannual AOT well and more information is needed to obtained seasonal AOT using visibility.