Spatial and temporal variation of Visible Infrared Imaging Radiometer Suite (VIIRS)-derived aerosol optical thickness over Shandong, China

Spatial and temporal variations in regional aerosol optical thickness (AOT) at 550 nm over Shandong Province, China, based on one year's Visible Infrared Imaging Radiometer Suite (VIIRS) data were investigated. The regional forest background (FB) annual mean AOT was 0.467 with a standard deviation of 0.339, which was much higher than the North America background continental AOT level of 0.10. Higher AOT values for the study region were mainly found in the spring and summer, especially from May to August, while the lowest mean values were seen in November and December. Urban areas all have obviously higher mean AOT values than those of the rural areas resulting from intense anthropogenic sources. Given that FB AOT represents the natural background level, we estimated that anthropogenic emissions and secondary aerosol generation contribute approximately 0.352 to aerosol loading in this region. Additionally, strong regional imbalance of AOT was found to be distributed over the study area. The maximum annual average AOT values occurred in inland cities, while coastal cities usually had lower AOT values.