| Summary: | High-spatiotemporal-resolution PM<sub>2.5</sub> data are critical to assessing the impacts of prolonged exposure to PM<sub>2.5</sub> on human health, especially for urban areas. Satellite-derived aerosol optical thickness (AOT) is highly correlated to ground-level PM<sub>2.5</sub>, providing an effective way to reveal spatiotemporal variations of PM<sub>2.5</sub> across urban landscapes. In this paper, Multi-Angle Implementation of Atmospheric Correction (MAIAC) AOT and ground-based PM<sub>2.5</sub> measurements were fused to estimate daily ground-level PM<sub>2.5</sub> concentrations in Beijing for 2013–2017 at 1 km resolution through a linear mixed effect model (LMEM). The results showed a good agreement between the estimated and measured PM<sub>2.5</sub> and effectively revealed the characteristics of its spatiotemporal variations across Beijing: (1) the PM<sub>2.5</sub> level is higher in the central and southern areas, while it is lower in the northern and northwestern areas; (2) the PM<sub>2.5</sub> level is higher in autumn and winter, while it is lower in spring and summer. Moreover, annual PM<sub>2.5</sub> concentrations decreased by 24.03% for the whole of Beijing and 31.46% for the downtown area from 2013 to 2017. The PM<sub>2.5</sub> data products we generated can be used to assess the long-term impacts of PM<sub>2.5</sub> on human health and support relevant government policy decision-making, and the methodology can be applied to other heavily polluted urban areas.
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