Spatio-Temporal Characteristics of Aerosol Optical Depth and Their Relationship with Urbanization over Beijing-Tianjin-Hebei Region

This study validated the applicability of Terra MODIS (MOderate-resolution Imaging Spectroradiometer) C006 3 km aerosol products over Beijing-Tianjin-Hebei region. The spatiotemporal variations of aerosols were analyzed using Aerosol Robotic Network (AERONET) data from 2008 to 2012. Based on the application of the Defense Meteorological Satellite System (DMSP) Operational Linescan System (OLS) nighttime light data as an assessment method, the correlation of urbanization development and aerosol optical depth (AOD) was investigated. The results revealed that:(1) MODIS 3 km AOD and AERONET data were consistent in the study region with a correlation coefficient of 0.91, which meets the requirements of NASA's error; (2) annual areal mean AOD varied between 0.361 and 0.453 over the study area during 2008-2012, and downward but not significant trends occurred in the past five years due to the large inter-annual variation; seasonal average AOD rose substantially in the autumn and winter and dropped in the spring and summer; (3) high AOD values were mainly found in South-Central Hebei, Beijing, and Tianjin, while low values were concentrated in northern Hebei; distribution of seasonal average AOD showed large seasonal variation; (4) spatial distributions of AOD agreed well with that of nighttime light in Beijing-Tianjin-Hebei region, and the R² of Geographically Weighted Regression (GWR) model results of AOD and nighttime light is about 0.8. The results indicated that the AOD distribution is positively correlated with nighttime light. Urbanization development and human activity have significant impacts on the variation of AOD.