Monitoring particulate matter with aerodynamic diameters of less than 2.5 µm (PM 2.5 ) is of great importance to assess its adverse effects on human health, especially densely populated regions. In this paper, an improved linear mixed effect model (LMEM) was developed. The model introduced meteorological variable, column water vapor (CWV), which has as the same resolution as satellite-derived aerosol optical thickness (AOT), to enhance PM 2.5 estimation accuracy by considering spatiotemporal consistency of CWV and AOT. The model was implemented to urban agglomeration of Chengdu Plain during 2015. The results show that model accuracy has been improved significantly compared to linear regression model (R 2 = 0.49), with R 2 of 0.81 and root mean squared prediction error (RMSPE) of 15.47 µg/m 3 , mean prediction error (MPE) of 11.09 µg/m 3 , and effectively revealed the characteristics of spatiotemporal variations PM 2.5 level across the study area: The PM 2.5 level is higher in the central and southern areas with dense population, while it is lower in the northwest and southwest mountain areas; and the PM 2.5 level is higher during autumn and winter, while it is lower during spring and summer. The product data in this paper are valuable for local government pollution monitoring, public health research, and urban air quality control. widely used for AOT retrieval, e.g., advanced very high-resolution radiometer (AVHRR), total ozone mapping spectrometer (TOMS), moderate-resolution imaging spectroradiometer (MODIS), multi-angle imaging spectroradiometer (MISR), sea-viewing wide field-of-view sensor (SeaWifFS) [16], and visible infrared imaging radiometer suite (VIIRS) [17], continuously measuring AOT from the late 1990s to the most recent.Satellite data are able to monitor large/urban scale air quality through adding synoptic and spatial distribution information to ground-based air quality measurements and modeling [18,19]. In recent decades, numerous researchers have developed many algorithms for calibrating satellite-derived AOT to ground-level PM 2.5 concentrations. Early studies primarily established simple linear regression models to relate PM 2.5 and AOT [19][20][21]. Then, meteorological data were incorporated in the multiple regression analysis and improved the PM 2.5 -AOT correlation [22]; advanced statistical models, such as artificial neural networks (ARN) [23], generalized additive model (GAM) [24,25], land use regression model (LUR) [26][27][28], and geographically weighted regression (GWR) [29][30][31][32][33] were developed to analyze the variability of PM 2.5 -AOT relationship correlated with meteorology or land use data. Although such advanced models gained higher estimation accuracy for large regions such as the northeastern and southeastern US, Europe, and China, etc., auxiliary parameters increased the complexity of these models and introduced other errors. Lee firstly incorporated time-varying parameters (day-to-day) in a statistical model to calibrate MODIS AOT and obtained good estimation accurac...